Mauna Loa SP-28 - History

Mauna Loa SP-28 - History


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Mauna Loa

A former name retained. The second Mauna Loa is named for a 13,680-foot volcano in the Hawaii Volcanoes National Park, island of Hawaii.

I

(SP-28: t. 18 (gr,) ; 1. 56'; b. 9'6"; dr. 2'9"; s. 20 k.; cpl. 7; a. ling.)

The first Mauna Loa, a motor yacht, was built by George Lawley & Sons, Noponset, 'Mass., in 1916; acquired by the Navy under free-lease contract from A. C. James 10 May 1917; and commissioned the next day.

Mauna Loa was called in for special duty during World War 1, operating off the Ist Naval District until the Armistice. She decommissioned 5 December and was returned to her owner the same day.


Mauna Loa: The World’s Biggest Volcano

Mauna Loa (/ˌmɔːnə ˈloʊ.ə/ or /ˌmaʊnə ˈloʊ.ə/ Hawaiian: ˈmɐwnə ˈlowə English: Long Mountain) is the world’s largest active volcano. It is the classic shield volcano, with broad, rounded sides and a Hawaiian name that means “long mountain.” It is one of five volcanoes that make up the Hawaiian Island, which is located in the Pacific Ocean and belongs to the United States of America. Its lengthy submarine flanks plunge another 5 km (16,400 ft) to the sea bottom, which is further depressed another 8 km by Mauna Loa’s massive mass (26,200 ft).

Mauna Loa (meaning “Long Mountain” in Hawaiian) is one of the world’s largest single mountain masses, rising to 13,677 feet (4,169 meters) above sea level and covering half of the island’s area. Its dome measures 75 miles (120 kilometers) in length and 64 miles (103 kilometers) in width. It is an active shield volcano with relatively moderate slopes, with a volume of around 18,000 cubic miles (75,000 km3), despite the fact that its peak is about 125 feet (38 m) lower than Mauna Kea’s. Mauna Loa lava outbursts are silica-poor, extremely fluid, and generally non-explosive.

However, it is more remarkable because it rises 30,000 feet (9,144 m) from the seabed, which is higher than Mount Everest. Under the weight of this massive mountain, the ocean floor literally bends. Mauna Loa’s land mass is nearly equivalent to the total land mass of all of the other Hawaiian Islands. Mauna Loa has been erupting for at least 700,000 years, and it may have first risen above sea level around 400,000 years ago. The oldest rocks that have been dated are less than 200,000 years old.

While an eruption of the volcano that dominates the landscape isn’t imminent, scientists watching the unrest on Hawaii’s largest island believe Mauna Loa’s lengthy slumber may be coming to an end. It is one of the world’s most active volcanoes, while not erupting as frequently as its younger cousin Kilauea. When it erupts, it usually does so in a big way, resulting in massive torrents of lava that have frequently threatened Hilo.

A cinder cone and surrounding flows on Mauna Loa

The magma for the volcano comes from the Hawaii hotspot, which over tens of millions of years has been responsible for the formation of the Hawaiian island chain. Within 500,000 to one million years, Mauna Loa will be carried away from the hotspot by the sluggish movement of the Pacific Plate, and it will become extinct. Moku‘weoweo, the peak caldera, is roughly 6 square miles (15 square kilometers) in size and 600 feet deep (180 metres). Mauna Loa eruptions have historically been characterized by large volume flows that create lava that can travel vast distances, contributing to the island’s form.

The most recent eruption of Mauna Loa occurred between March 24 and April 15, 1984. There have been no recent lethal eruptions of the volcano, but eruptions in 1926 and 1950 destroyed towns, and Hilo is largely built on lava flows from the late 1800s. Because this volcano reaches nearly 9 kilometers above sea level and the immense mountain’s weight has depressed the marine crust by around 8 kilometers, the total pile of volcanic material created by Mauna Loa is likely to be around 17 kilometers. It covers a surface area of 5,271 km2 (2,035 sq mi) and spans a maximum width of 120 km (75 mi), making it the world’s largest subaerial and second largest total volcano (after Tamu Massif).

Since its first well-documented historical eruption in 1843, Mauna Loa has erupted 33 times, making it one of the world’s most active volcanoes. Since 1868, it has produced enormous, voluminous basalt flows that have reached the ocean eight times. It covers more than half of the surface area of the island of Hawai’i, containing roughly 65,000 to 80,000 km3 (15,600 to 19,200 cu mi) of solid rock. Mauna Loa has two rift zones to the northeast and southwest, as well as a primary summit caldera called Moku‘āweoweo. The two rift zones have historically been quite active, with flows flowing toward Hilo in 1984 and South Kona in 1950.

When the volcano’s broad undersea flanks (5,000 m (16,400 ft) and 4,170 m (13,680 ft) subaerial height are added together, Mauna Loa climbs 9,170 m (30,085 ft) from base to summit, surpassing Mount Everest’s 8,848 m or 29,029 ft elevation from sea level to summit. Half of the eruptions reported from Mauna Loa have remained restricted to the remote summit area, indicating that an eruption does not always entail a hazard to people or property. Several eruptions, however, have resulted in lava streaming all the way to the ocean in a couple of hours. It’s just impossible to know what will happen ahead of time.

Since 1843, Mauna Loa has erupted 33 times, once every five years on average. Over a longer length of time, it is thought to have erupted once every six years for the past 3,000 years. Mauna Loa is shaped like a shield volcano, with a long, broad dome stretching down to the ocean floor and steep slopes of roughly 12 degrees at its steepest points due to its incredibly flowing lava. It erupts from both its top, which is occupied by a huge caldera, and its flanks’ NE and SW rift zones.

Mauna Loa continued to erupt, with three (in 1887, 1919, and 1926) partially subaerial eruptions in 1887, 1892, 1896, 1899, 1903 (twice), 1907, 1914, 1916, 1919, and 1926. In particular, the 1926 eruption is notable for inundating a settlement near Hoʻōpūloa, destroying 12 houses, a church, and a small harbor. The most recent eruption of Mauna Loa, which occurred in 1984, saw lava reach the outskirts of Hilo, which is home to the University of Hawaii, on the other side of the island, but only after several weeks of warning.

Almost 90% of Mauna Loa’s surface is covered by lava flows younger than 4000 years, approximately 50% by lava flows no older than 1500 years, and about 25% by lava flows less than 750 years. Since then, Mauna Loa has not erupted, and as of 2020, it has been silent for nearly 35 years, the longest stretch of silence in recorded history. Between 1950 and 1984, Mauna Loa was dormant for 34 years, with the exception of modest activity in 1975. Its recent inactivity is unlikely to be long-term, as even a century of low activity in Mauna Loa’s several hundred-thousand-year lifetime is a fairly short timeframe.


Company-Histories.com

Address:
2445 McCabe Way, Suite 250
Irvine, California 92614-4293
U.S.A.

Statistics:

Private Company
Incorporated: 1976
Employees: 295
Sales: $15.4 million (2003)
NAIC: 311911 Roasted Nuts and Peanut Butter Manufacturing


Company Perspectives:
Hawaii's perfect growing conditions, and Mauna Loa's matchless attention to quality at every step of processing, has earned Mauna Loa Macadamia Nut Corporation its premium reputation as the leader in macadamias.


Key Dates:
1881: The first macadamia tree in Hawaii is planted.
1922: The first macadamia nut company is launched.
1946: Mauna Loa's orchards are planted by Castle & Cooke.
1973: C. Brewer buys Castle & Cooke's macadamia nut operations.
1976: The Mauna Loa Nut label is created.
1986: Buyco, Inc. acquires C. Brewer.
2000: The Shansby Group acquires Mauna Loa.

With it corporate headquarters located in Irvine, California, and its processing facility in Hilo, Hawaii, Mauna Loa Macadamia Nut Corporation is the largest processor and marketer of macadamia nut products in the world. The private company, named after the largest active volcano in the world, markets nuts from 10,000 acres of orchards planted on the Big Island of Hawaii on the slopes of Mauna Loa volcano. Macadamia trees are highly fragile, their shallow roots putting them at risk to high winds. To provide a windbreak, pines trees usually ring the macadamia trees. They are also bred to be suitable to all micro-climates of the Big Island, offering something of a hedge if overly wet or dry conditions prevail during the course of a year. Because macadamia seedlings are so genetically unstable, commercial nut-bearing trees are created by grafting onto rootstock in a nursery, where they are kept for two years. The trees are then transferred to an orchard, but a dozen years will pass before they are producing at commercial levels. Mature nuts fall off the trees naturally and are harvested five times a season, which lasts from mid-August to March. In contrast to the trees, the macadamia nut is the hardest nut in the world, requiring 300 pounds per square inch of pressure to crack the shell. Further, the nut requires an extensive drying, separation, and dry roasting process, which leads in large part to the product's high price. In addition to selling salted and unsalted dry roast macadamias and honey-roasted macadamias, Mauna Loa also offer a number of confections relying on macadamias, including a variety of chocolate covered macadamias, candy-coated macadamias, nut and fruit mixes, macadamia candy bars, and macadamia cookies.

Macadamia Tree Named in 1857

The macadamia tree was not native to Hawaii. Rather, it originated in Australia, and in 1857 was named after Dr. John Macadam, a chemistry professor at the University of Melbourne and a member of Australia's Parliament who apparently had nothing to do with the plants. His friends, Baron Ferdinand von Muller, head of Melbourne's Botanic Gardens, along with Walter Hill, the superintendent of Brisbane's Botanic Gardens, were the first to classify the tree botanically, having discovered it on an expedition. The honor of providing a name fell upon von Muller, who elected to pay tribute to his friend Macadam. Hill removed the kernels from the shells in order to plant and cultivate the trees. He believed the nuts were likely poisonous, according to some aborigines at least, and was shocked to discover a young assistant happily snacking on some. When the boy seemed to suffer no ill effects, Hill tried the kernels, found them delicious, and became an enthusiast.

The man responsible for introducing the macadamia tree to Hawaii was William H. Purvis, who was a manager of a sugar plantation on the Big Island. While visiting Australia, he was so taken by the beauty of the macadamia tree that he brought back seeds to Hawaii and in 1881 planted them to adorn his house, uninterested in their nuts. Brothers E.W. and R.A. Jordan in 1892 were also successful in planting seeds at their home in Nu-Uanu. Macadamia trees thrived in the Hawaiian climate, but for the next thirty years they were valued mostly for their appearance, although residents of Hawaii had in the meantime learned to appreciate the flavorful macadamia nut. It was Massachusetts-born Ernest Van Tassel who commercialized the macadamia nut, having first tasted it at a cocktail party in 1916 after coming to Hawaii for his failing health. Because his health improved, he looked for a way to show his gratitude, and he decided to plant a macadamia orchard for the purpose of sharing the delicacy with other people and perhaps establishing a new industry on the islands. With seeds from the Purvis and Jordan trees, he leased 25 acres of government land near Honolulu to plant them, and in 1922 he created Hawaiian Macadamia Nut Co., Ltd.

Van Tassel was not experienced in agriculture, and his initial efforts at commercializing macadamia nut production proved unsuccessful because seedlings from the same tree produced nuts that differed wildly in terms of quality and yield. With the help of the University of Hawaii, a method of grafting was developed and over the course of 20 years nine strains of the macadamia were developed that were able to produce a consistently high quality nut. In the meantime, Van Tassel was able to begin commercial processing of macadamia nuts on a limited basis in 1934 under the brand name Van's Macadamia Nuts. Also in the 1930s, Ellen Dye Candies and the Alexander Young Hotel candy shop began to sell chocolate-covered macadamia nuts, and by the end of the decade Hawaiian Candies & Nuts Ltd. was marketing macadamias under the Menehune Mac label.

The consortium of corporations known as the "Big Five," which had dominated the Hawaiian economy for more than 100 years, took note of the macadamia nut's emergence and began to become involved. Castle & Cooke, best known as the owners of the Dole Pineapple Co., planted the orchard that would form the foundation of Mauna Loa Macadamia Nut Corp. in 1946 on the Big Island near Kea'au. In 1948, Castle & Cooke organized the Royal Hawaiian Macadamia Nut Company, but it was not until 1954 that trees began to bear fruit, and another two years would pass before the first commercial crop was available. Full production would not be achieved on the company's holdings until 1965, at which point a state-of-the-art processing plant was built near Hilo. The plant was ahead of its time in that it was designed to supply its own power by burning macadamia shells.

Mauna Loa Created in 1976

Another major Big Five company to become involved in macadamia nuts was C. Brewer and Company Ltd., which formed subsidiary Royal Iolani. Long involved in running sugar plantations, C. Brewer began divesting its sugar operations in the early 1970s, when sugar became an unprofitable commodity, and looked elsewhere for opportunities. In 1973, it bought Castle & Cooke's macadamia nut orchard and processing plant, which was doing about $4 million in annual business. Royal Iolani changed its name to Mauna Loa Macadamia Nut Corp in 1976 and began marketing its nuts under the Mauna Loa label. It was also in 1976 that C. Brewer began to convert five sugar plantations to macadamia cultivation, turning over 1,000 acres each year. In the late 1970s, Mauna Loa found a way to fund its expansion by selling off its nut orchards to private investors in small parcels. As part of the deal, Mauna Loa would buy the nuts produced under a long-term contract.

With the loss of sugar as a strong cash crop, many Hawaii agriculturalists believed that macadamia nuts held the most potential to make up the loss in business. However, macadamia nuts remained very much a delicacy enjoyed while staying in Hawaii or on the airplane during the flight to the islands. In large part, people on the mainland bought macadamia nuts as a way to relive their Hawaiian vacation. Although Mauna Loa was by far the largest producer of macadamia nuts, it faced serious challenges from other Hawaiian growers as well as from nuts grown in South America and elsewhere. The result was a glut of macadamias and concern that the market was simply not large enough for the gourmet nut. In the early 1980s, Mauna Loa began to advertise on the mainland (advertising ceased in 1988) and in 1984 moved its marketing division to Los Angeles in order to make further inroads in the mainland market, where it established regional distribution centers in New York, Atlanta, Chicago, and Los Angeles. In addition, Mauna Loa looked to the Japanese market, signing a distribution contract with Suntory, Ltd. Another answer was to find a way to add value to the product. In 1985, Mauna Loa opened a 10,000-square-foot chocolate factory. In this way, the company could increase the value of substandard nuts by making candy out of them. In addition, this strategy served to expand the appeal of macadamias. Mauna Loa also continued its program of selling small orchards to real estate syndicates, in many cases to visiting investors, as a way to fund its diversification efforts and plans to continue converting old sugar land to macadamia cultivation. In 1985, the company launched a ten-year program to sell off orchards in 30-acre parcels. At the same time, it purchased much of the land it had been leasing as a way to accumulate additional orchard land to sell to investors. Buyers had the option of signing a farm management contract, but no formal agreement was necessary in order to sell the nuts to Mauna Loa, which was always in the market to acquire the harvests.

In the mid-1980s, C. Brewer's corporate parent, IU International Corporation, decided to spin-off the Hawaiian company. C. Brewers' chief executive officer, John "Doc" Buyers, who had turned around the business ten years earlier, making it something of a cash cow for IU, was given the opportunity to head the spin-off. However, because IU suffered severe losses in 1985 and was burdened by an inordinate amount of debt, it was unable to afford the spin-off. Rather than take his chances with new owners, Buyers assembled a group of investors, formed a company called Buyco, Inc., and bought C. Brewer, including Mauna Loa. The sale of macadamia orchards was a key component in the financing, as Buyers sold shares in a master limited partnership, Mauna Loa Macadamia Partners, which packaged more than 2,400 acres of macadamia nut orchards. The offering raised about $35 million of the approximate $207 million purchase price for C. Brewer. Moreover, Buyco retained a management contract to farm, process, and sell the nuts produced by the orchards.

Sluggish Growth in the 1990s and New Owners in 2000

In the 1990s, Mauna Loa was far from aggressive in growing the business. The company increased its output of macadamia nuts and allowed the market for the product to essentially grow at its own pace. The company overcame some problems, such as a lawsuit from mainland buyers who charged that Mauna Loa and Mac Farm International Inc. conspired to fix the price of mac- adamia nuts. Another concern was a tree disease, Macadamia Quick Decline (MQD), which cost Mauna Loa some 25,000 trees over the course of a five-year period. A more positive development was the signing of a distribution agreement with the Planters Division of Nabisco Foods Group for the sale of Mauna Loa nuts on the U.S. mainland. In 1994, that relationship was severed when Mauna Loa formed a mainland marketing and sales division, headed by Scott C. Wallace. In 1998, Wallace was named president and chief operating officer for the company, working out of Irvine, California, a move that began the transition of the corporate office from Hawaii to Irvine.

In September 2000, Mauna Loa changed ownership as part of a restructuring of C. Brewer, which Buyers now wanted to reposition as an agricultural services company in alliance with the local biotechnology industry. Mauna Loa was sold to the Shansby Group, a San Francisco private equity group founded in 1987 by J. Gary Shansby, a former CEO who was responsible for growing Shaklee Corporation from a small family business to a Fortune 500 company. Along with partner Charles H. Esserman, Shansby invested in a number of brand consumer products, including The Famous Amos Chocolate Chip Cookie Co., Terra Chips, and La Victoria Foods.

Under the Shansby Group, Mauna Loa made a number of changes. Scott Wallace was named CEO and the headquarters relocated to Irvine. Mauna Loa resumed advertising on the mainland, which led to a major increase in sales. The company also expanded its product offerings, so that in spite of a significant macadamia nut shortage in the early 2000s, Mauna Loa enjoyed an annual growth rate in the 40 percent range. To make up for the lack of nuts, the company became adept at quickly launching products that did not rely on the entire kernel, such as trail mixes, cookies, caramel corn, toffee, and brittle. After decades in business, Mauna Loa was finally coming of age in its marketing approach. It now leveraged the strength of the Mauna Loa brand name, which management believed connoted more than just macadamia nuts and could be associated in the consumer mind with anything tropical. Not only would the company continue to expand its slate of confectionary products, it might acquire other food business in order to create a premium products company centered on the Mauna Loa name.

Principal Competitors: Hawaiian Host Inc Mac Farms of Hawaii Inc. Kraft Foods Inc.

  • Furlong, Tom, "Macadamias Helping to Bring Hawaii out of Its Shells as an Exporter," Los Angeles Times , May 29, 1988, p. 5.
  • Koepke, Bill, Stephen W. Knox, and Richard Ha, "Putting Down Roots," Hawaii Business , November 1985, p. 66.
  • MacNeil, Karen, "The Noblest of Nuts," St. Petersburg Times , October 12, 1989, p. 1D.
  • Porrazzo, Kimberly A., "Custom Packages Lure Buyers," OC Metro , March 18, 2004, p. 32.
  • Rodrigo, Christine, "Hawaii's Mac Nut Crop Threatened by Disease," Pacific Business , July 8, 1991, p. 34.

Source: International Directory of Company Histories , Vol.64. St. James Press, 2004.


Mauna Loa, Hawaii, 1984

On average, Mauna Loa, located on the island of Hawaii in the Pacific Ocean, erupts every three and a half years with fountains and streams of incandescent lava. Following a year of increased seismicity, Mauna Loa began erupting at 1:25 am on March 25, 1984. The outbreak began along a fissure that split the long axis of the summit caldera, an oval, cliff-bounded basin approximately 3 to 5 km (1.9 to 3.1 miles) from rim to rim that had been formed by prehistoric subsidence. Lava fountains along the fissure formed a curtain of fire that illuminated the clouds and volcanic fumes into a red glow backlighting the black profile of the volcano’s huge but gently sloping summit. Lava from the summit fissure ponded in the caldera, and the first observers in the air reported that much of the caldera floor was covered by a lake of orange-red molten rock, which quickly cooled to a black crust with zigzag-shaped fractures that were still incandescent.

At dawn the summit fissure began to propagate down the northeast rift zone, and a new line of lava fountains formed at an elevation of 3,800 metres (12,500 feet). Two hours later the fracture extended an additional 6 km (3.7 miles) down the northeast rift, forming another curtain of fire about 2 km (1.2 miles) long and 50 metres (164 feet) high at an elevation of 3,450 metres (11,300 feet). As new vents opened at lower elevations, the higher vents stopped erupting. The vents at 3,450 metres continued to erupt throughout the early afternoon, sending a small lava flow down the high southeast flank of Mauna Loa. At about 4:00 pm the lava fountains dwindled, and a swarm of new earthquakes indicated that the fissure was propagating even farther down the rift. It stopped opening some 7 km (4.3 miles) down the ridge at an elevation of 2,900 metres (9,500 feet), where new and final vents opened at 4:40 pm .

The output of lava from these final vents was vigorous. Although the fountains were only about 20 metres (66 feet) high, the volume of lava produced amounted to approximately 500,000 cubic metres (about 17.6 million cubic feet) per hour. In 24 hours the river of lava flowed 12 km (7.5 miles) northeast toward the city of Hilo. The vents erupted steadily for the next 10 days. Even though the eruption rate remained high, the advance of the front of the lava flow slowed, traveling 6 km (3.7 miles) on the second day, 4 km (2.5 miles) on the third day, and 3 km (1.9 miles) on the fourth day. This progressive slowing of the lava front had several causes. The lava supply was increasingly starved at lower altitudes by a slow widening of flows at higher elevations, by thickening of flows at higher elevations through overplating (that is, accumulation of new layers on top of layers only a few hours or days old), and by branching of the flows upstream into new lobes that robbed the lower flows of their lava. An additional cause was the thickening and widening of flows at lower elevations where the slope of the land is more gradual.

By April 5, output from the vents at 2,900 metres (9,500 feet) had begun to wane, and the eruption was over by April 15. The longest flows had traveled 27 km (16.8 miles), stopping at an elevation of 900 metres (3,000 feet)—10 km (6 miles) from the outskirts of Hilo. The total volume of the eruption was 220 million cubic metres (7.7 billion cubic feet), and new lava flows covered 48 square km (18.5 square miles). No one was hurt, and the only significant damage was the cutting of power lines and the blocking of a few jeep roads.

The temperature of the erupting lava was 1,140 °C (2,084 °F) and its viscosity was about 10 3 poise (dyne-second per cm 2 ), which is roughly equivalent to the viscosity of liquid honey at 20 °C (68 °F). A household analog of a Hawaiian lava flow in miniature is the slow and erratic advance of molten wax as it adds new lobes to a pile of candle drippings.

Mauna Loa’s massive outpourings of lava have made it the world’s largest volcano. Its summit rises 4,170 metres (13,680 feet) above sea level and more than 9,000 metres (29,500 feet) above the seafloor surrounding the Hawaiian Ridge. The volume above its base, which has subsided well below the adjacent seafloor, is estimated to be about 75,000 cubic km (18,000 cubic miles).

Kilauea, a smaller and younger volcano on the southeast side of Mauna Loa, has been erupting lava from 1983 to the present. Its output of lava has averaged about 400,000 cubic metres (14 million cubic feet) per day, in sharp contrast to the 12 million cubic metres (424 million cubic feet) per day during the first week of the 1984 eruption of Mauna Loa. It is this slow but steady effusion of molten lava that has allowed the eruption of Kilauea to continue so long. Apparently, magma from depth is replacing the amount being erupted at a balanced rate. In contrast, the effusion of lava at Mauna Loa in 1984 was at a much more rapid rate than that at which magma could be resupplied from depth, and the eruption was soon exhausted. Both Mauna Loa and Kilauea were erupting at the same time in 1984. Even though the difference in elevation between the vents on Mauna Loa and Kilauea was only 2,000 metres (6,600 feet), there was no apparent effect of one eruption upon the other. This indicates that, although both volcanoes have the same general source region of magma about 60 km (37 miles) below the surface, their conduits and shallower magma chambers are separate.


Mauna Loa SP-28 - History

click on the image for a larger version. The sketch at left is by Joseph Nawahi. It shows the 1881 lava flow approaching Hilo on February 21. Image courtesy of National Park Service, Hawaii Volcanoes National Park, HAVO 394, Volcano House Guest Register 1873 to 1885 via Big Island News. (Color and contrast balance in Photoshop from the original by K. Rubin, HCV)

1855-56 Eruption

     Read the full account of the 1855-56 Mauna Loa lava flow entering Hilo at this link. The history is in part based on an account by Titus Coan, whose autobiography is proudly hosted on our HCV website.

    short summary: The eruption began with high fountaining and a lava flow in 1855, continued downslope through early 1856. By mid year it had stalled six miles from Hilo Bay (just above what is now Kaumana City subdivision) although the eruption at the vent continued.

    Mauna Loa erupted most recently in 1984. The eruption started at the summit (in Moku'aweoweo crater, which is the grey oblong area in the lower-left corner of the image to the left), extended in to the upper Southwest Rift Zone, and then migrated to the Northeast Rift Zone on the first day of the eruption. Volcanic activity remained in the northeast rift for 21 days. This sequence of events resulted in three flow units (shades of red to the left) the flows are numbered 1, 2 and 3 in the image. The a'a flow system from the lower vents achieved a maximum length of 27 km within a few days of inception of the eruption. The total lava flow was near 220 million m³. As eruption rates declined, the main a'a flow evolved from a simple narrow lobe with an efficient channel that delivered virtually the entire vent output to within 1 km of the flow toe, to an upright-stagnating channel system characterized by levees, blockages, ponds, and complexly branching overflows.

    Radiocarbon dating of charcoal from beneath lava flows of Mauna Loa has provided the most detailed prehistoric eruptive history of any volcano on Earth. After accounting for contradictory dates and averaging multiple dates on single flows, there are at least 170 "reliable" ages on separate lava flows (Lockwood, USGS Professional Paper 1350). This number of dated flows makes up about 35% of the total number of mapped prehistoric Mauna Loa flows, which is a very significant proportion.

    The distribution of these ages has revealed fundamental variations in the time and place of Mauna Loa eruptive activity, particularly for Holocene time. As lava flow activity from Mauna Loa's summit waxes, activity on the rift zones wane. A cyclic model has been proposed (by Lockwood, ibid.) which involves a period of concentrated summit, shield-building activity associated with long-lived lava lakes and frequent overflows of pahoehoe lavas on the north and southeast flanks. During these periods, compressive stresses across Mauna Loa's rift zones are relatively high, inhibiting eruptions in these areas. These periods are then followed by a relaxation of stresses across Mauna Loa's rift zones and a long period of frequent rift zone eruptions as magma migrates downrift. This latter eruptive style is marked by summit caldera collapse (possibly associated with massive eruptions of picritic lavas low on the rift zones). Concurrent with this increased rift zone activity, the summit caldera is gradually filled by repeated smaller summit eruptions then, stress across the rift zone increases, magma rises more easily to the summit, rift activity wanes, and the cycle repeats itself.

    Two such cycles have been recognized within the late Holocene, each lasting 1,500-2,000 years. However, evidence for earlier such cycles is obscure. Mauna Loa appears to have been quiescent between 6-7 ka, for unknown reasons. A period of increased eruptive activity marked the period of 8-11 ka, coincident with the Pleistocene-Holocene boundary. Other volcanoes on the island of Hawaii for which (limited) radiocarbon data are available show no evidence of similar cyclicity or repose.

Some of Mauna Loa's larger eruptions
Year Volume x 10 6 m³ Area km² Eruption Source
1843 202 45 North Flank
1852 182 33 Northeast Rift
1855-1856 280 66 Northeast Rift
1859 383* 91* North Flank
1868 123* 24* Southwest Rift
1873 630 5 Summit
1880-1881 130 57 Northeast Rift
1887 128* 29* Southwest Rift
1907 121 28 Southwest Rift
1919 183* 28* Southwest Rift
1926 121* 35* Southwest Rift
1933 100 6 Summit
1940 110 13 Summit
1942 176 34 Northeast Rift
1949 116 22 Summit
1950 370* 112* Southwest Rift
1975 30 13 Summit
1984 220 48 Northeast Rift
* denotes flows erupted above and below sea level. The numbers given are for the above sea level parts of these flows only.
Eyewitness Accounts of these Mauna Loa eruptions can be found in various chapters of our on-line version of Life in Hawai`i by the Rev. Titus Coan (originally published in 1882)
[ 1843 | 1852 | 1855-1856 | 1868 & 1877 | 1880]

This page created by Ken Rubin with assistance from Rochelle Minicola
maintained by Ken Rubin ©,
Rochelle contributed her work in the late 1990s under the auspices of the Kailua High School Community Quest work experience program, in cooperation with the Hawaii Center for Volcanology.
Other credits for this web site.


Historic Ascents of Mauna Loa

The summit of Mauna Loa was visited by prehistoric Hawaiians for ceremonial purposes. They constructed the Ainapo Trail from their closest village, Kapapala to the rim of Moku'aweoweo caldera. The Ainapo Trail had a series of shelters that were stocked with drinking water and fire wood. The Hawaiian method of ascent involved moving upslope in easy segments to lessen fatigue and to allow proper acclimatization. Footwear for the climb usually involved wrapping the feet with tea leaves or merely going barefoot. The major stages were a series of overnight camps, complete with small, warm, thatched houses and supplied with food water and firewood. Smaller stages were areas used as frequent rest stops in natural rockshelters, caves and lava tubes. Ascents of Mauna Loa by prehistoric Hawaiians were made during summit eruptions, when the godess Pele was present to honor her with chants, prayers and offerings. The first non-Hawaiian credited with climbing Mauna Loa is Archibald Menzies. Menzies was the surgeon/naturalist for the 1791-1795 Voyage of Discovery led by Captain George Vancouver of the British Navy. An expedition set out on Feb. 6 1794 from Kealakekua Bay with Chief Luhea in a large double hulled canoe that belonged to King Kamehameha. Menzies reached the summit of Mauna Loa on Feb. 16, 1794 where he used barometric readings to calculate the summit elevation at 13,564 ft. An excerpt from Menzies journal: "We managed to boil the chocolate in a tin pot over a small fire made of our walking sticks, and each had his share of it warm, with a small quantity of rum in it, before we went to bed. . as it was agreed we should all sleep together to keep ourselves warm, we joined together everything we had for our general covering, made pillows of hard lava, and in this [way] was passed the night. Febuary 16. Next morning, at sun-rise, the Thermometer was at 26 degrees and the air was exceedingly keen and piercing. About 11 in the forenoon we arrived at the mouth of an immense crater. [we] crossed over this rugged hollow after a hard struggle, and by noon got to the highest part of the mountain, on the western brink of the great crater, where I observed the Barometer. "


Mauna Loa SP-28 - History

  • United States
  • Hawaii and Pacific Ocean
  • Shield
  • 1984 CE
  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 19.475°N
  • 155.608°W
  • 4170 m
    13681 ft
  • 332020
  • Latitude
  • Longitude
  • Summit
    Elevation
  • Volcano
    Number
Most Recent Weekly Report: 26 June-2 July 2019 Cite this Report

HVO reported that during the previous several months earthquake and ground deformation rates at Mauna Loa were elevated above background levels. During the first half of 2018 the seismic network recorded fewer than 20 shallow, small-magnitude earthquakes per week. Following a significant earthquake swarm in October, the rate increased to at least 50 events per week beneath the summit, upper Southwest Rift Zone, and upper west flank. These locations were similar to those that preceded eruptions in 1975 and 1984. GPS and satellite RADAR data detected deformation consistent with recharge of the shallow magma storage system. The increased seismicity and deformation indicated that Mauna Loa is no longer at background levels, prompting HVO to raise the Aviation Color Code to Yellow and the Volcano Alert Level to Advisory. HVO noted that an eruption was not imminent.

Most Recent Bulletin Report: May 2012 (BGVN 37:05) Cite this Report

2004-2010 deformation trends intrusive bodies modeled

Mauna Loa has remained non-eruptive since April 1984. We previously reported on an April-October 2004, deep, long-period (LP) earthquake swarm and associated brief period of contraction ( BGVN 29:09). After that and through 2010, deformation continued at variable rates and with brief pauses. During 2004-2010, HVO reported little variation in gas emissions at Mauna Loa.

The material in this report is drawn from monitoring data collected by the USGS Hawaiian Volcano Observatory (HVO) and, in particular, Interferometric Synthetic Aperture Radar (InSAR) data provided by HVO's Mike Poland. A subsection below discusses the use of deformation data as a basis for modeling inferred magma bodies in the subsurface at Mauna Loa (Amelung and others, 2007).

Slowed edifice inflation. Increased rates of inflation following the April-October 2004 deep LP earthquake swarm continued through 2007, when HVO reported that GPS and InSAR-based inflation rates had slowed substantially. Comparison of radar interferograms covering two intervals (11 October 2003-19 November 2005 and 24 March 2007-17 April 2010) highlights the slowed deformation rates during the latter interval (figure 24). To better understand the technique used to observe the slowed rate of deformation at Mauna Loa, see the next section.

Figure 24. Radar interferograms of Mauna Loa covering the time intervals of (a) 11 October 2003-19 November 2005 and (b) 24 March 2007-17 April 2010. These interferograms highlight the slowing of inflation during the latter interval. The large number of color bands ('fringes') in (a) indicates an increased rate of inflation compared to the fewer number of fringes in (b). As depicted in the scale bar (bottom center), concentric and cyclical sets of fringes indicate a ground movement of 2.83 cm towards the satellite's line-of-sight during the time interval shown in each image. The images were produced from data acquired by the European Space Agency's Environmental Satellite (ENVISAT), with an incidence angle of 25° from the ground, looking W to E. Courtesy of Michael Poland, USGS-HVO.

InSAR technique to monitor deformation. A technique has emerged that enables scientists to create an image of where and how much displacement occurred over a ground or glacial (ice) surface (e.g., Rosen and others, 2000). The technique's spatial coverage is variable from hundreds of square meters to hundreds of square kilometers. Measurements of the component of deformation along the instrument's line-of-sight typically have centimeter-scale precision. While the precision may be less than some other deformation techniques (i.e., GPS monitoring or tilt measurements), the broad coverage can pinpoint particularly interesting patterns and help define areas for collateral studies, including further modeling of the causes of deformation (see next section).

The image, which is called a radar interferogram, compares two separate 'snapshots' acquired at distinct points in time. The snapshots are radar images of the topography of the ground surface in the area of interest (figure 25) acquired by an instrument mounted on an airplane or satellite. The images are generated by transmitting radar waves to the earth's surface the radar waves then reflect (backscatter) and are measured upon their return to the instrument. To make one interferogram, two such images taken at different times are compared. Variations in the phase of the coherent radar signal in the two snapshots disclose areas where displacement occurred along the instrument's line-of-sight (example radar waves A-E, figure 25). In some cases scientists collect and process enough data to enable them to make a time series of interferograms, for example, annual interferograms that enable yearly comparisons of the ground surface over a decade of time.

Figure 25. A cartoon representation of the basic principles of radar interferometry. As the satellite makes its first pass over a ground surface ('Initial ground surface'), it collects radar waves reflected off of the ground surface (solid wave, 'pass 1'). During a subsequent orbit (often months to years later), when the satellite again passes over the same ground surface, another collection is made from very nearly the same orbital location (dashed wave, 'pass 2'). If the ground surface deformed during the time between data collections (e.g., 'Subsided ground surface'), then the collected radar waves of the second pass will be out of phase compared to those collected during the first pass (example waves A-E, at right). The phase difference of the waves is then converted into the component of ground motion along the line-of-sight of the satellite (either towards or away from the satellite), and is represented by a color as part of a full color cycle. Since the technique is based on the phase difference of multiple waves, the accuracy is constrained by detectable fractions of the radar wave's wavelength. In figure 24, C-band radar (wavelength = 5.6 cm) was used. Image not drawn to scale. Image created by GVP staff.

On the interferograms, interference patterns appear as full color cycles, or 'fringes', indicating how far out of phase the radar waves are when they return to the satellite (figure 25) one fringe indicates a line-of-sight ground offset equivalent to one half of the radar waves' wavelength. An increased number of fringes at a specific area within an image thus indicates increased deformation during the time between images, allowing estimation of deformation rates over the time period analyzed. Our discussion of this technique has omitted various assumptions, sources of error, and corrections used to process and interpret the data.

Magma chamber and dike modeling . Amelung and others (2007) assessed measured ground deformation at Mauna Loa from InSAR data. They modeled the size, location, and geometry of inferred intrusive bodies beneath Mauna Loa that led to the observed surface deformation. Their modeling suggested a spherical magma chamber of 1.1 km radius, centered under the SE caldera margin at 4.7 km depth below the summit (0.5 km below sea level), and a vertical dike with most of its inflation occurring along an 8-km-long zone at depths of 4-8 km (Figure 26). The dike's direction of opening was normal to its inferred planar orientation. An HVO model, fit to ground-based GPS measurements, agrees with the model of Amelung and others (2007).

References. Amelung, F., Yun, S.H., Walter, T.R., Segall, P., and Kim, S.W. (2007) Stress Control of Deep Rift Intrusion at Mauna Loa Volcano, Hawaii. Science, 316 (5827), pg. 1026-1030 (DOI: 10.1126/science.1140035).

Rosen, P.A., Hensley, S., Joughin, I.R., Li, F.K., Madsen, S.N., Rodriguez, E., and Goldstein, R.M. (2000) Synthetic aperture radar interferometry, Proc. IEEE, 88, 333- 382.

Information Contacts: Michael Poland, Hawaiian Volcano Observatory (HVO) , U.S. Geological Survey, PO Box 51, Hawai'i National Park, HI 96718, USA (URL: https://volcanoes.usgs.gov/observatories/hvo/) Christelle Wauthier , Department of Terrestrial Magnetism, Carnegie Institute of Washington, Washington, DC.

Weekly Reports - Index
26 June-2 July 2019 Cite this Report

HVO reported that during the previous several months earthquake and ground deformation rates at Mauna Loa were elevated above background levels. During the first half of 2018 the seismic network recorded fewer than 20 shallow, small-magnitude earthquakes per week. Following a significant earthquake swarm in October, the rate increased to at least 50 events per week beneath the summit, upper Southwest Rift Zone, and upper west flank. These locations were similar to those that preceded eruptions in 1975 and 1984. GPS and satellite RADAR data detected deformation consistent with recharge of the shallow magma storage system. The increased seismicity and deformation indicated that Mauna Loa is no longer at background levels, prompting HVO to raise the Aviation Color Code to Yellow and the Volcano Alert Level to Advisory. HVO noted that an eruption was not imminent.

20 June-26 June 2018 Cite this Report

On 21 June HVO reported that seismicity and deformation at Mauna Loa had been at near-background levels for at least the previous six months. The Aviation Color Code was lowered to Green and the Volcano Alert Level was lowered to Normal. During 2014 through most of 2017 seismicity was variable but elevated, and ground deformation was consistent with an influx of magma in the shallow reservoir.

16 March-22 March 2016 Cite this Report

On 17 March HVO reported that seismicity at Mauna Loa remained above long-term background levels and was characterized by shallow earthquakes occurring beneath the Southwest Rift Zone (SRZ) at depths of less than 5 km. GPS data showed continuing deformation related to inflation of a magma reservoir beneath the summit and upper SRZ, with inflation recently detected in the SW part of the magma storage complex. The Aviation Color Code remained at Yellow and the Volcano Alert Level remained at Advisory.

16 September-22 September 2015 Cite this Report

On 18 September HVO reported that for at least the previous year the seismic network at Mauna Loa detected elevated seismicity beneath the summit, upper Southwest Rift Zone, and W flank the rate of these shallow earthquakes varied but overall had remained above the long-term average. The earthquakes locations were similar to those preceding recent eruptions in 1975 and 1984, although the magnitudes were comparatively low. In addition, ground deformation consistent with recharge of the volcano’s shallow magma storage system was also detected during the previous year. The rate and pattern of the deformation was similar to that measured during a period of inflation 2005, unrest that did not lead to an eruption. However, since the observations indicated that Mauna Loa is no longer at background levels, HVO raised the Aviation Color Code to Yellow and the Volcano Alert Level to Advisory.

24 March-30 March 2010 Cite this Report

On 30 March, HVO reported that the Aviation Color Code and the Volcano Alert Level for Mauna Loa were both lowered to Green and Normal, respectively. Deformation had not been noted since mid-2009 and seismicity was at normal levels.

17 August-23 August 2005 Cite this Report

HVO reported on 21 August that extension across Mauna Loa's summit had resumed over the previous few weeks after pausing for much of July. Seismicity remained at low levels at the volcano.

13 October-19 October 2004 Cite this Report

According to HVO, since early July 2004 an increased number of earthquakes had been recorded from beneath Mauna Loa. From week to week, the numbers fluctuated but remained well above the norm. During the week ending 13 October, 110 earthquakes were located under the summit, up from 47 for the week ending 6 October. Through 13 October, more than 730 earthquakes related to the ongoing seismic activity have been centered beneath Mauna Loa's summit caldera and the adjacent part of the southwest rift zone.

6 October-12 October 2004 Cite this Report

According to HVO, since early July 2004 an increased number of earthquakes had been recorded from beneath Mauna Loa. From week to week, the numbers fluctuated but remained well above the norm. Through September, more than 580 earthquakes were centered beneath Mauna Loa's summit caldera and the adjacent part of the southwest rift zone. Most of these earthquakes were quite deep, from 35 to 50 km below the ground surface and small, less than M 3. They were "long-period" (LP) earthquakes, which means that their signals gradually rise out of the background rather than appearing abruptly. Such a concentrated number of deep LP earthquakes from this part of Mauna Loa is unprecedented, at least in the modern earthquake record dating back to the 1960s. During about 4-11 October, however, only 23 earthquakes were located under the summit.

22 September-28 September 2004 Cite this Report

No changes were noted by HVO at Mauna Loa through 27 September. Since early July 2004, an increasing number of earthquakes had been recorded from beneath Mauna Loa. From week to week the numbers fluctuated but remained well above the earlier established norm. Through the third week of September, more than 560 earthquakes were centered beneath Mauna Loa's summit caldera and the adjacent part of the southwest rift zone. Most of these earthquakes were quite deep, 35-50 km below the surface, and less than M 3. Inflation continued at the summit and showed no change during the increased seismic activity.

15 September-21 September 2004 Cite this Report

No changes have been noted by HVO at Mauna Loa through 21 September. Since early July 2004, an increasing number of earthquakes has been recorded from beneath Mauna Loa. From week to week the numbers fluctuate but remain well above the earlier established norm. Through the second week of September, more than 500 earthquakes were centered beneath the summit caldera and the adjacent part of the southwest rift zone. Most of these earthquakes were quite deep, 35-50 km below the surface, and less than M 3. Inflation was continuing at the summit and has so far shown no change during the increased seismic activity.

8 September-14 September 2004 Cite this Report

HVO reported that beginning in early July 2004 an increasing number of earthquakes had been recorded beneath Mauna Loa. From week to week, the numbers fluctuated but remained well above the norm. Through the first week of September, more than 350 earthquakes were centered beneath Mauna Loa's summit caldera and the adjacent part of the southwest rift zone. Most of these earthquakes were quite deep, from 35 to 50 km below the ground surface. They were "long-period" (LP) earthquakes, which means that their signals gradually rise out of the ambient seismic background. Such a concentrated number of deep LP earthquakes from this part of Mauna Loa is unprecedented, at least in the modern earthquake catalog dating back to the 1960s. Inflation continued at the summit and as of 12 September showed no change during the increased seismic activity.

14 May-20 May 2003 Cite this Report

HVO reported on 18 May that inflation may have resumed at Mauna Loa's summit during the week, after slackening off following an increase in mid-February. Seismicity, however, remained low. Inflation was noted where the GPS network first showed definite lengthening of the lines across the summit caldera in late April or May 2002, after nearly 10 years of slight deflation. HVO interpreted the lengthening, uplift, and tilting to indicate resumed swelling of the magma reservoir within the volcano.

12 March-18 March 2003 Cite this Report

HVO reported on 16 March 2003 that renewed inflation at Mauna Loa's Moku`aweoweo summit caldera began in late February 2003. The GPS network first showed inflation in late April or May 2002, which tailed off and perhaps stopped in mid-winter. The lengthening, uplift, and tilting were interpreted to indicate resumed swelling of the magma reservoir within Mauna Loa. Seismicity remained at low levels.

22 January-28 January 2003 Cite this Report

HVO reported on 27 January that during the previous couple of months the rate of lengthening across Mauna Loa's summit caldera (Moku`aweoweo) slowed significantly. The lengthening started in late April or May, as did uplift measured by GPS and ground tilt measured by several dry-tilt stations. As of the 27th, seismicity remained at low levels.

30 October-5 November 2002 Cite this Report

On the afternoon of 1 November volcanic tremor, centered low on Mauna Loa's SE flank, occurred for 30 minutes. HVO stated that this is a common occurrence, taking place several times a year in the same general region. The permanent, continuous GPS network indicated ongoing lengthening across Moku`aweoweo summit caldera, as it has since late April or May 2002.

23 October-29 October 2002 Cite this Report

As of 28 October Mauna Loa continued to inflate, but seismicity remained at low levels. The permanent, continuous GPS network indicated ongoing lengthening across Moku`aweoweo summit caldera, as it has since late April or May 2002.

9 October-15 October 2002 Cite this Report

A brief period of low-amplitude tremor occurred at Mauna Loa's summit on 7 October, lasting several minutes. It apparently was triggered by, or at least quickly followed, a small earthquake. The following day, several more small earthquakes took place. By the 10th, seismicity had returned to low levels. During 8-15 October, the permanent continuous global positioning system network indicated that ongoing lengthening occurred across Moku`aweoweo summit caldera as it has since late April or May.

25 September-1 October 2002 Cite this Report

HVO reported on 30 September that a pattern of slow deflation occurring at Mauna Loa for the past 9 years abruptly changed in mid-May when the summit area began to slowly swell and stretch. Global Positioning System measurements revealed that distances across the summit caldera (Moku`aweoweo) have been lengthening at a rate of 5-6 cm per year, and the caldera has widened about 2 cm since 12 May. The summit area was slightly higher than before mid-May, consistent with swelling. In addition, the upper part of the SE flank showed outward movement. Seismicity remained low at Mauna Loa, although it may have been slightly higher level than during the pre-inflation interval.

1 May-7 May 2002 Cite this Report

A small earthquake cluster event, with magnitudes between 1.1-1.7, occurred at Mauna Loa during 19-26 April. There were no signs indicating that an eruptive event was imminent and no significant deformation was recorded.

Bulletin Reports - Index

Reports are organized chronologically and indexed below by Month/Year (Publication Volume:Number), and include a one-line summary. Click on the index link or scroll down to read the reports.

07/1975 (CSLP 48-75) Lava fountains in the summit caldera and along two rift zones

11/1976 (NSEB 01:14) Increased seismicity during 20-24 November

01/1978 (SEAN 03:01) New fumarolic activity and increased inflation rate

05/1983 (SEAN 08:05) Seismicity and summit caldera deformation increase

03/1984 (SEAN 09:03) Fissure eruption produces voluminous lava flows from NE rift vents SO2-rich tropospheric plume reduces visibilities 7,000 km away

04/1984 (SEAN 09:04) Major NE Rift Zone eruption ends total eruption volume

10/1987 (SEAN 12:10) Steady post-1984 reinflation eruption but seismicity low

02/1989 (SEAN 14:02) 50% of 1984 deflation recovered no shallow seismicity

09/2002 (BGVN 27:09) Following 9 years of slow deflation, quicker inflation since mid-May 2002

09/2004 (BGVN 29:09) Deep, long-period earthquake swarm and contraction in July and August 2004

05/2012 (BGVN 37:05) 2004-2010 deformation trends intrusive bodies modeled

Information is preliminary and subject to change. All times are local (unless otherwise noted)

July 1975 (CSLP 48-75)

Lava fountains in the summit caldera and along two rift zones

Card 2212 (07 July 1975) Lava fountains in the summit caldera and along two rift zones

Mauna Loa volcano began erupting at 2344 hours HST, 5 July 1975 (0944 GMT 6 July). By 0200 July 6th a line of fountains extended the length of the summit caldera in a N30°E direction through the cones of 1940 and 1949. Fresh lava covered most of the caldera floor, and overflowed from both South Pit and North Pit. Fountains extended for about 2 km beyond the caldera margin into the southwest rift zone, and new flows traveled as much as 3 km down the flanks of the volcano both southward and westward and partly filled the pit craters Lua Honhonu and Lua Hou. Fountains also extended into the northeast rift zone and ultimately reached 3 km beyond the margin of North Pit.

Caldera activity stopped between 0400 and 0500, soutwest rift zone activity stopped about 0600, and activity concentrated in the northeast rift zone along two en echelon fissures 1 km long at an elevation of about 3,780 m. Major flows from these fountains traveled 5 km ENE along the rift zone and 6 km NNE down the N flank. Activity continued through the morning, declined in the afternoon, and all fountains ended by early evening.

Frequent earthquakes centered along the northeast rift zone and harmonic tremor are continuing as of 0300 on 7 July.

Information Contacts: Robert Tilling and Donald W. Peterson , Hawaiian Volcano Observatory, USGS.

November 1976 (NSEB 01:14) Cite this Report

Increased seismicity during 20-24 November

A substantial increase in the number of earthquakes beneath Mauna Loa was recorded 20-24 November (table 1). On the morning of 25 November, only one earthquake was recorded (beneath the NE rift). The USGS predicts a major eruption of Mauna Loa within the next 18 months.

Table 1. Earthquakes recorded at Mauna Loa during 20-24 November 1976.

Date Event Totals
20 Nov 1976 350
21 Nov 1976 200-300
22 Nov 1976 200-300
23 Nov 1976 more than 300
24 Nov 1976 less than 100

January 1978 (SEAN 03:01) Cite this Report

New fumarolic activity and increased inflation rate

The July 1975 eruption of Mauna Loa has been described by Lockwood and others (1976). Soon after this eruption, Mauna Loa began to inflate, and, chiefly on the basis of the historic patterns of activity, the USGS predicted that a second eruption, followed soon thereafter by a larger eruption from the NE rift, was likely to occur before July 1978. During the first half of 1977, however, local seismicity and inflation rates declined considerably, and in July 1977 the USGS issued a press release withdrawing the "before July 1978" date for the predicted eruption. Seismicity beneath the summit region has remained low, but measurements made in December 1977 indicate that the inflation rate for June-December 1977 had increased to that recorded during 1976. Furthermore, dense fume clouds have been emitted from the 1975 eruptive fissures since October 1977. The USGS has installed gas monitoring devices on one of these fumaroles and is continuing to monitor the volcano closely.

Reference. Lockwood, J., Koyanagi, R., Tilling, R., Holcomb, R., and Peterson, D., 1976, Mauna Loa threatening: Geotimes, v. 21, no. 6, p. 12-15.

Information Contacts: G. Eaton , HVO, Hawaii.

May 1983 (SEAN 08:05) Cite this Report

Seismicity and summit caldera deformation increase

"Mauna Loa last erupted in July 1975. That eruption was preceded by an increase in both shallow and intermediate-depth earthquakes, and by extension of survey lines across the caldera (figure 1, left). Since 1980, and especially since early 1983, the number of shallow earthquakes beneath Mauna Loa has been increasing again. Intermediate-depth earthquakes have continued at a higher rate during the period from 1978 to present than during 1971-73, but have not shown the same pattern of increase as they did in 1974 (figure 1, right). Figure 1 also shows a recent increase in the rate of extension of survey lines across the summit caldera.

Figure 1. Plot of cumulative number of local earthquakes at shallow (0-5 km) and intermediate (5-13 km) depths, and extension (in mm) on two survey lines across the summit caldera, for 1970-75 (left), and 1978-83 (right).

"The recent rate of strain from apparent intrusion of magma beneath the summit region shows an increasing trend from both seismic and ground surface deformation data. The present strength of the summit region is not known, so no precise forecast of the next eruption can be made. However, the present seismic and deformation data indicate a significantly increased probability of eruption of Mauna Loa during 1983 or 1984."

Information Contacts: R. Decker , R. Koyanagi , and J. Dvorak , HVO, Hawaii.

March 1984 (SEAN 09:03) Cite this Report

Fissure eruption produces voluminous lava flows from NE rift vents SO2-rich tropospheric plume reduces visibilities 7,000 km away

The following (except for the plume data) is from HVO. Times noted below are preliminary and subject to slight revision after later analysis. "A long-expected flank eruption of Mauna Loa began on 25 March, and had ended by 14 April.

Background. "When summit seismic activity increased sharply in April 1974, Mauna Loa had not erupted since June 1950. Measurement of EDM lines across the summit caldera (Mokuaweoweo) in the summer of 1974 revealed significant extensions, monitoring capabilities were increased, and a forecast of renewed activity was issued (Koyanagi and others, 1975). The summit eruption of 5-6 July, 1975 lasted for less than 20 hours, and only about 30 x 10 6 m 3 of lava were erupted. The eruption was identical to numerous other Mauna Loa summit eruptions that had been followed within 3 years by large flank eruptions. Given the historic record and continuing inflation, a forecast was made for renewed eruptive activity sometime before the summer of 1978 (Lockwood and others, 1976). The 1976 forecast was rescinded in 1977 but slow inflation continued and another forecast (based on an increase in the rate of geodetic change and seismic activity) was issued in 1983. This called attention to the increased probability of a Mauna Loa eruption within the next two years' (Decker and others, 1983), but see SEAN 08:05 in which the forecast was more specific: 'a significantly increased probability of eruption of Mauna Loa during 1983 or 1984.'

Premonitory activity. "The 25 March outbreak gave almost no short-term instrumental warning. Seismic activity had been increasing gradually through March (figure 2), but was relatively low immediately preceding the outbreak only 29 microearthquakes were recorded beneath the summit caldera during the preceding 24 hours (in contrast to 700 microearthquakes/day in September 1983).

Figure 2. Number of earthquakes per day at Mauna Loa, 1 January-5 April. The start of the eruption is indicated by an arrow.

"Several people saw probable fume clouds from the summit caldera and a camper at the summit noted small explosions from the 1975 eruptive fissures on 23 March. One hiker had reported seeing 'glowing cracks' near the 1940 cone on 18 March, but no anomalous activity was detected on a thermal probe in the 1975 fumaroles. Oxidation state and temperatures of fumarolic gases remained essentially unchanged prior to the last satellite transmission about midnight on 24 March.

Eruption narrative. "At 2255 on 24 March, a small earthquake swarm began directly beneath the summit. Weak harmonic tremor with an amplitude of about 1 mm was recorded at the summit station (WIL, figure 3) at 2330. The number of small summit earthquakes increased at 2350. Tremor amplitude recorded at the summit increased to about 5 mm at 0015 on 25 March, remained high at 0051, and was recorded on all Mauna Loa and Kilauea summit area stations.

Figure 3. Sketch maps of the NE rift zone and summit of Mauna Loa, showing positions of 1984 lava flows (stippled) as of 5 April. Eruption fissures are indicated by hachured lines. The edge of the suburbs of Hilo is shown by a dotted line on the NE rift zone map. The areas covered are shown by the index map (inset).

"At 0055 a magnitude 4.0 earthquake beneath the summit awoke geologists (from the University of Massachusetts) camped at Pu'u Ula'ula on the NE Rift Zone. At 0056, the telescope at the summit of Mauna Kea (42 km NNW of Mauna Loa) began high-amplitude oscillation, preventing astronomical observations for the next few hours. Between 0051 and 0210, 11 earthquakes with magnitudes between 2.0 and 4.1 were recorded beneath the summit. At 0100 borehole tiltmeters recorded the onset of rapid summit inflation.

"A military satellite detected a strong infrared signal from the summit at 0125. Glow was sighted in the SW portion (1940 cone area) of the summit caldera by an observer on the summit of Mauna Kea at 0129, by the geologists at Pu'u Ula'ula at 0130, and from Kilauea at 0140. At 0146, fountain reflection on fume clouds observed from HVO suggested that fountaining extended across much of SW Mokuaweoweo and was migrating down the SW Rift Zone.

"At 0232 the tops of fountains within Mokuaweoweo were seen from Pu`u Ula`ula, suggesting a height greater than 100 m. At approximately 0340, fountaining ceased on the SW Rift Zone. At 0357, 30-m-high fountains migrated out of Mokuaweoweo, down the upper NE Rift Zone. Lava flowed downrift and onto the SE flank.

"At approximately 0600, fountaining in the caldera gradually ended. At 0632, a new vent opened about 700 m E of Pohaku Hanalei and 8 minutes later another en echelon fissure began to erupt about 600 m downrift. Lava appearance was preceded by 3 minutes of copious white steam emission from the fissure. For the next 2.5 hours, activity waned.

"At 0905, profuse steaming appeared on a fracture at about 3,510 m altitude, and at 0910 fountaining 15-40 m high began at 3,410 m and migrated downrift. At 0930, fountains above Pohaku Hanalei died down as lava production increased to approximately 1-2 x 10 6 m 3 /hour along a 2 km-long curtain of fire between about 3,400 and 3,470 m. The loci of most vigorous fountaining alternated along the 2-km fountain length. Much of the production from these vents was consumed by an open fissure parallel to and S of the principal fissure upslope, although an aa flow did move 5 km SE, S of an 1880 flow. During activity of these vents, episodic turbulent emissions of red and brown `dust' from the eruptive fissures sent clouds to about 500 m height. At 1030, steaming was noted along a 1-km-long crack system extending from about 3,260-3,170 m, but there was no further downrift migration of eruptive vents for several hours. At about 1550, ground cracking extended below 3,000 m, and at 1641 eruptive vents opened at about 2,800 m and migrated both up- and downrift. At 1830 an eruptive vent extended about 1.7 km from about 2,770-2,930 m elevation. Fountains to 50 m height fed fast-moving flows to the E and NE. Activity waned at the 3,400-m vents.

"By 0640 the next day, all lava production had ceased above 3000 m. Fountains (to 30 m height) were localized along a 500-m segment of the fissure that had opened the previous afternoon. The fastest moving flow cut the power line to the NOAA Mauna Loa Observatory shortly before dawn. At 0845, the E flows were spread out over a wide area above 1,900 m elevation, but their advance slowed during the day. Four principal eruptive vents then developed along this fissure system. Two vents fed the NE flow (1), while the other two fed the S (2-4) flows. Flow 1 steadily advanced downslope 27-28 March (figure 4), between the 1852 and 1942 lava flows. Approximately 80% of the lava production fed flow 1. Flows 2-4 ceased significant advance by 28 March. The terminus of flow 1 stopped significant advance by early 29 March, while production at the vents remained essentially constant. This suggested that a new branch flow had developed upslope. Bad weather prevented confirmation of the new branch until 30 March. This new flow (1A) moved rapidly downslope, N of flow 1.

Figure 4. Rates of movement of flows 1, 1A, and 1B in kilometers per day. Small circles represnet observations of flow positions. Courtesy of J.P. Lockwood.

"Phase 17 of Kilauea's E Rift Zone eruption began that morning but had no apparent effect on Mauna Loa activity. Likewise Kilauea tilt showed no deflection at the time of the Mauna Loa outbreak on 25 March.

"Flow 1A slowed on 31 March as the feeding channel became sluggish, and the flow thickened and widened upstream. At 1215 on 5 April, the flow was moving very slowly (18 m/hour) slightly below 900 m elevation. A major overflow at about 2,000 m shut off most of its lava supply and created a fast-moving flow (lB), which advanced 3 km NE to about 1,800 m elevation by 1700.

Deformation. "Much of the NE rift zone geodetic monitoring network was measured shortly before the 25 March outbreak, and EDM, tilt, and gravity stations were re-measured several times during the eruption. Although continuously recording tiltmeters at the summit showed sharp inflation (dike emplacement) immediately preceding the outbreak, major subsidence of the summit region accompanied eruptive activity along the NE rift. The center of subsidence, near the S edge of the summit caldera (figure 5), was coincident with the center of uplift identified from repeated geodetic surveys between 1977 and 1983. The amount of summit deflation recorded by tilt and horizontal distance measurements exceeded the amount of gradual inflation of the volcano since the July 1975 summit eruption, suggesting substantial injection of magma into the summit area prior to this eruption, and possibly prior to the first EDM line across the summit caldera in 1964. Maximum vertical elevation change, inferred from repeated gravity measurements, is 500 mm.

"Large extensions occurred across the middle NE rift zone during dike emplacement on 25 March, but EDM monitor lines across this zone showed no significant change after the initial dilation. The rate of summit subsidence initially followed an exponential decay, similar to subsidence episodes in the summit region of Kilauea. Since 30 March, tilt and horizontal distance measurements have indicated a steady rate of deflation (figures 6 and 7), although measurements on 6 April suggest decreasing deflation rates.

Dike propagation. "All dikes were emplaced within the first 15 hours of the eruption. The eruptive fissure (surface expression of dikes) extended discontinuously along a 25-km zone from 3,890 m on the SW rift zone to about 2,770 m on the NE rift zone. Ground cracking along most of this zone demonstrates the continuity of the dike at shallow levels. Lateral propagation rates vary from >2,500 m/hour down the SW rift zone to about 1,200 m/hour in lower parts of the NE rift zone (figure 8).

Figure 8. Rate of propagation of eruption fissures, shown as distance from the 1940 cone (in the SW part of the summit caldera) vs. hours after the start of the eruption.

Petrography, lava temperatures, and gas measurements. "Hand specimens of the 1984 basalt are very fine-grained with widely scattered (<1%) phenocrysts of olivine <3 mm in diameter and sparse microphenocrysts of plagioclase and clinopyroxene. Most olivines are anhedral, resorbed, commonly kinked, and surprisingly forsteritic (Fo88-90). Plagioclase and clinopyroxene are barely resolvable in the groundmass. Maximum temperatures determined repeatedly by thermocouple and radiometer ranged from 1,137 to 1,141°C and had not changed as of 5 April.

"Eruptive gases have been extensively sampled and analyzed. Observed C/S ratios are much lower than expected in primitive Hawaiian tholeiite, suggesting extensive degassing in a shallow (<4 km deep) magma reservoir.

Geoelectric studies. "One self-potential (SP) profile, first measured in July 1983, exists across the NE Rift Zone about 1 km W of the main erupting vents. The first complete reoccupation of the SP line 3 days after the eruption's start showed an amplitude increase slightly > l00 mV centered over a zone about 300 m wide across the 1.5 km-long crack zone N of Pu'u Ula'ula. VLF measurements show that the dike is located nearly in the center of the cracked zone, directly beneath the pre-existing SP maximum, at a very approximate depth of 150 m.

Areal extent and volume of lava. "As of 5 April, 25-30 km 2 of area was covered. The lava is mostly pahoehoe near the vents, but is mostly aa more than 2 km from the vents. The volume was estimated to be about 150 x 10 6 m 3 by 5 April."

Eruption plume. The eruption produced a large gas plume that was carried thousands of kilometers to the W. The plume from the summit caldera activity was clearly visible from HVO. An airline pilot approaching Honolulu at dawn 25 March reported that the top of the plume was between 10.7 and 11 km altitude and was drifting SW. Observers at Honolulu airport tower (300 km NW of Mauna Loa) reported that the top of a tall cumulus-like cloud became visible S of the airport just before dawn.

There was no evidence that the plume reached the stratosphere the tropopause on 25 March was at about 18 km altitude. The plume was carried W by trade winds. By 30 March, a haze layer was detected at Wake and Johnston Islands (3,900 km W and 1,400 km WSW of Mauna Loa table 2). Haze reached Kwajalein (4,000 km WSW of Mauna Loa) the next day and had reached Guam (6,300 km WSW of Mauna Loa) by 2 April.

Table 2. Visibilities at airports on several islands affected by the plume from Mauna Loa (distances are from Mauna Loa). All times are Hawaiian Standard Time. Note that all except Johnston Island are across the International Date Line from Hawaii. Data courtesy of NOAA.

Island Distance Visibility Date and Time (1984)
Johnston 1,400 km WSW 6 km 2200 on 2 April - 0200 on 3 April
Wake 3,900 km W 1.6 km 1200 on 2 April - 1700 on 2 April
Ponape 5,000 km WSW 3.2 km 1000 on 2 April - 1400 on 2 April

SO2 emitted by Mauna Loa was detected by the TOMS instrument on the Nimbus 7 polar orbiting satellite, which passed over Hawaii daily at about local noon (figure 9). Although the TOMS instrument was designed to measure ozone, it is also sensitive to SO2. An algorithm has been developed to isolate SO2 values and calculate its approximate concentration within pixels (picture elements) roughly 50 km in diameter. Preliminary estimates of the total SO2 in the Mauna Loa plume, using TOMS data, were roughly 130,000 metric tons on 26 March and 190,000 metric tons on 27 March.

Figure 9. Preliminary SO2 data from the TOMS instrument on the Nimbus-7 satellite. All values less than 10 milliatmosphere-cm (100 ppm-meters) have been supressed. Each number or letter represents the average SO2 value within an area 50 km across. 1 = 11-15 matm-cm = 101-150 ppm-m, 2 = 16-20 matm-cm = 151-200s ppm-m, etc 9 is followed by A, B, C, etc. Courtesy of Arlin Krueger.

References. Decker, R.W., Koyanagi, R.Y., Dvorak, J.J., Lockwood, J.P. Okamura, A.T. Yamashita, K.M., and Tanigawa, W.R., 1983, Seismicity and surface deformation of Mauna Loa volcano, Hawaii: EOS, v. 64, no. 37, p. 545-547.

Koyanagi, R.Y., Endo, E.T., and Ebisu, J.S., 1975, Reawakening of Mauna Loa volcano, Hawaii a preliminary evaluation of seismic evidence: Geophys. Res. Letters, v. 2, no. 9, p. 405-408.

Information Contacts: J. Lockwood and HVO staff , Hawaii M. Rhodes , Univ. of Massachusetts M. Garcia , Univ. of Hawaii T. Casadevall , CVO, Vancouver, WA A. Krueger , NASA/GSFC M. Matson , NOAA/NESDIS.

April 1984 (SEAN 09:04) Cite this Report

Major NE Rift Zone eruption ends total eruption volume

"The NE Rift Zone eruption, which began on 25 March, ended early on the morning of 15 April. Lava output and fountain vigor steadily decreased during the last week of the eruption. As flow channels became blocked (by sluggish aa and channel collapse breccias) progressively farther upslope, flows terminated higher on Mauna Loa's NE flank. Many short overflows of viscous aa, up to 15 m thick, moved less than a few hundred meters from these points of channel blockage. By 10 April, no lava flowed below 2,400 m. The total area covered by new lavas increased very little after 5 April, as multiple flows mostly piled on top of older flows. Total volume for this eruption was estimated at 180-250 x 10 6 m 3 ."

Information Contacts: J. Lockwood and T. Wright , HVO, Hawaii.

October 1987 (SEAN 12:10) Cite this Report

Steady post-1984 reinflation eruption but seismicity low

"Mauna Loa's latest eruption was in March-April 1984 on the Northeast rift zone. The eruption was associated with a large collapse (figure 10) and seismicity that peaked during and following the eruption (figure 11). Since 1984 the volcano has begun to reinflate, as shown by outward tilt and horizontal extension of Mauna Loa's summit area.

Figure 10. EDM data along three lines across Mauna Loa's summit caldera, January 1983-4 November 1987. HVO 93 is on the NW rim of the caldera, and the three lines cross the caldera in ESE, SE, and S directions, respectively, to the SE rim. Courtesy of HVO.
Figure 11. Daily number of recorded short-period (top) and long-period (middle) summit microearthquakes, and NE rift events (bottom) at Mauna Loa, January 1984-4 November 1987. Courtesy of HVO.

Seismicity. "Following the increase and peak in seismicity of the last eruption in Mar-Apr 1984, the number of shallow microearthquakes had slowly decreased (figure 11). Most of the post-eruption events were attributed to the gradual structural adjustments from the major deflation at the summit (resulting from the voluminous magma withdrawal) and the principal eruptive vent near Pu'u Ulaula on the Northeast rift zone. The post-eruption pattern of decreasing seismicity is indicated by the daily number of summit microearthquakes and Northeast rift events.

"There has been no significant seismic activity beneath the summit and rift zones of Mauna Loa since the 1984 eruption, and the present level of shallow seismicity is relatively low. There has been some increase in intermediate-depth events beneath the volcano noticed over the past year. Most of the events are very small, recorded only on a few summit and rift stations, and essentially < 0.5 in magnitude.

Ground deformation. "Deformation studies show that Mauna Loa reinflation has been steady at this writing the summit has recovered over 1/3 of the amount of subsidence that took place during the eruption, as measured by both dry tilt and cross-caldera EDM (figure 10).

"A forecast of the next Mauna Loa eruption will depend on two things: an increase in shallow earthquakes and tilt recovery. The last two eruptions showed a precursory period of 1 year (July 1975 eruption) and 4 years (March 1984 eruption) respectively from the time of increased seismicity to the onset of eruption. There is no absolute level of tilt recovery at which we can specify that Mauna Loa will erupt. However, we would consider roughly 90% recovery from the 1984 deflation would indicate a state of readiness to erupt. On the basis of the data shown here we would not expect a Mauna Loa eruption for at least five years. We will update this estimate as we continue to monitor tilt and seismicity . . . ."

Information Contacts: T. Wright , R. Koyanagi , and A. Okamura , HVO.

February 1989 (SEAN 14:02) Cite this Report

50% of 1984 deflation recovered no shallow seismicity

By 17 November 1988, when Mauna Loa's summit tilt network was relevelled, the summit region had recovered

50% of the deflation associated with the 1984 eruption (figures 12 and 13). Intermediate-depth microearthquakes have occurred at a moderate rate in the summit region. However, the abundant shallow seismicity that originated beneath the summit crater during the year before the 1975 eruption and for 4 years before the 1984 eruption has not been observed. The absence of such precursory shallow seismicity suggests to HVO geophysicists that the next eruption . . . is several years away.

Figure 12. Changes in N-S and E-W components of tilt at Mauna Loa, measured by station NEW MOK 2 on the NW rim of the caldera, 1 June 1983-17 November 1988.
Figure 13. Dry tilt changes near the summit of Mauna Loa from 23-27 April 1984 to 8-17 November 1988. Courtesy of T. Wright.

Information Contacts: T. Wright , HVO.

July 1991 (BGVN 16:07) Cite this Report

Surface deformation measurements indicate gradual reinflation of Mauna Loa's summit since its 1984 eruption. Earthquake counts have fluctuated, but have apparently increased since late 1990.

Two bursts of intermediate-depth volcanic tremor, beginning at about 1200 on 13 July, preceded a swarm of long-period earthquakes that continued for

14 hours. Activity peaked between 2300 on 13 July and 0100 the next morning. As the long-period events gradually declined, shallow microearthquake activity increased, and continued for about 6 hours. All of the events were too small for precise location.

The 13 July activity began

2 hours before an earthquake swarm under the summit of Kilauea. Seismicity at Mauna Loa has apparently returned to average background levels since mid-July.

Information Contacts: P. Okubo , HVO.

September 2002 (BGVN 27:09) Cite this Report

Following 9 years of slow deflation, quicker inflation since mid-May 2002

Mauna Loa is the southern-most volcano on the island of Hawaii. Following the last eruption of Mauna Loa, during March-April 1984 ( SEAN 09:03), there have been several periods of inflation and deflation at the volcano's summit caldera, Moku`aweoweo. As of September 2002, Mauna Loa has remained non-eruptive (figure 14) for 18.5 years. The pattern of deformation at Moku`aweoweo abruptly changed in mid-May 2002 from deflation to inflation, lasting until at least September 2002. An archive of deformation and seismic data from Mauna Loa dating back to the 1970s provides an example of the volcano's pre-eruptive and precursory behavior.

After the last Bulletin report about Mauna Loa in July 1991( BGVN 16:07) the volcano's summit continued to gradually inflate as it had since the 1984 eruption. This trend reversed in 1993-1994 when distances across the caldera shortened by as much as 7 cm, and leveling surveys in 1996 and 2000 measured more than 7 cm of subsidence SE of the caldera.

Beginning on 24 April 2002 at 0645 a notable cluster of deep earthquakes (darkest circles in figure 15) occurred in a 52-hour period. The earthquakes ended on 26 April at 1045. Many of the epicenters plotted within or close to the caldera's SW margin. The earthquakes ranged in depth from 26 to 43 km and in magnitude from 1.1 to 1.7. Several shallow earthquakes preceded this cluster the largest, a magnitude 2.5 event on 21 April at 1931, was located

3 km beneath the SW rift zone. After the cluster, several deep long-period events were recorded beneath the SW rift zone. At that time data from the continuous tiltmeter, dilatometer, and nearly continuous global positioning system (GPS) stations failed to suggest significant deformation of Moku`aweoweo caldera, upper-rift zones, or outer flanks.

Figure 15. Plot showing the magnitudes, locations, and depths of earthquakes registered at Mauna Loa during 7 April- 26 September 2002. Following the swarm of deep earthquakes during 24-26 April (dark circles), seismicity was somewhat elevated.

Inflation. HVO maintains several continuously recording GPS stations installed in 1999 (figure 16). Beginning in late April or early May 2002, deformation data began to show signs of renewed activity.

Figure 16. Map showing the several GPS stations HVO maintains on Mauna Loa as of September 2002. HVO plans to install several additional stations (white dots), on indefinite loan from Stanford University. Courtesy HVO.

Figure 17 shows the change in distance between MOKP and MLSP GPS stations, located on opposite sides of Moku`aweoweo. The increased distance between the two stations was interpreted to represent inflation of the summit magma reservoir, centered

5 km below the caldera. The small amount of extension marks a noticeable change from the pattern of deflation during the preceding 9 years. GPS measurements also revealed that the summit area had inflated about 2 cm, consistent with swelling.

Figure 17. Graph showing the change in distance between GPS stations MOKP and MLSP, located on opposite sides of Moku'aweoweo caldera, as seen during 4 October 2000-30 September 2002. Distance across Moku'aweoweo began to increase by 5-6 cm/year starting in late April-May 2002. Courtesy HVO.

The switch from slow deflation to more rapid inflation occurred around 12 May. GPS data indicated lengthening at a rate of 5-6 cm per year. Therefore, as of 26 September the caldera had widened about 2 cm since 12 May. Measurements at GPS stations farther out on the flanks showed that swelling occurred at more than the summit, in particular, the upper part of the SE flank was moving outward.

In order to test the precision of the GPS measurements, HVO compared the GPS data against dry-tilt method data at the summit, an independent means to measure ground deformation using land-surveying instruments, deployed at regularly visited stations. These confirmed the GPS results, though with less precision.

Electronic-tiltmeter data obtained at the Moku'aweoweo tiltmeter were also analyzed for changes in tilt direction. No significant volcanic tilt was recorded that deviated from the diurnal signal corresponding to daily temperature fluctuations, or an annual signal corresponding to seasonal temperature changes.

During the inflationary period, seismicity at Mauna Loa was at a somewhat elevated level following the 24-26 April earthquake cluster. But, it remained far lower than it was the months prior to the 1975 and 1984 eruptions.

May-September 2002 unrest in comparison to activity since 1974. For Mauna Loa these data sets are available: electric distance meter (EDM) measurements since about 1975, GPS observations since 1999, dry-tilt observations since 1975, and seismicity since 1974. The capability to detect unrest at Mauna Loa has increased in the past few years with the installation of many new, continuously recording electronic tiltmeters, GPS receivers, and strainmeters (figure 18).

Figure 18. Map showing locations of continuously recording instruments for measuring deformation and seismicity at Mauna Loa as of September 2002. This map omits many additional benchmarks used in various deformation surveys. Courtesy HVO.

Figure 19 shows the distance measured across Moku`aweoweo caldera between MOKP and MSLP benchmarks by EDM during 1975 to September 2002, and by GPS beginning in 1999. Abrupt extensions associated with the 1975 and 1984 eruptions were caused by the rise of magma from the summit reservoir to the surface. During the 1984 eruption, the summit area subsided rapidly as lava erupted. When the eruption stopped, the summit reservoir again began to inflate in response to the influx of magma, as indicated by the increasing distance between the two benchmarks until about1993. Inflation did not occur again until early May 2002 when the slow contraction across the summit changed abruptly to extension. This extension rate is the highest since immediately after the 1984 eruption.

Figure 19. The change in distances across Moku`aweoweo caldera at Mauna Loa, between MOKP and MSLP benchmarks (see map inset) as measured by electronic distance meter since about 1975 to September 2002 and by GPS receivers since 1999. Note the abrupt change from contraction to extension in May 2002. Courtesy HVO.

GPS measurements have only been made at Mauna Loa since 1999, but in that relatively short time an abrupt change in ground movement has been recorded (figure 20). Measurements made during January 1999-May 2002 show small velocities of ground displacement towards the SW. In contrast, during May-September 2002 the direction of ground motion changed from a fairly uniform, southeastward movement to a predominately radial pattern. In addition, the rate of ground motion increased by 5 to 10 times.

Figure 20. Velocities of ground displacement measured by GPS stations on Mauna Loa during 1999 to 12 May 2002 (light lines) and 12 May to 21 September 2002 (black lines). The arrows represent the speed and direction of motion. The tips of the arrows representing the actual motion point lie somewhere within the uncertainty ellipses. Courtesy HVO.

Ground tilt away from the caldera occurs when magma accumulates beneath the surface. Although electronic measurements provide much more precise readings, the dry-tilt method remains in use at HVO after 35 years for several reasons. First, the measurements can be made nearly anywhere at any time. Second, they are not subject to long-term instrument drift. Lastly, they provide an independent corroboration of measurements made by more sophisticated modern instruments. Dry-tilt measurements revealed the following: inflation between the 1975 and 1984 eruptions (figure 21a), inflation after the 1984 eruption, continuing until 1993 (figure 21b), and deflation from 1993 through March (probably May) 2002 (figure 21c). After March (probably May), the tilt returned to an inflationary pattern (figure 21d). The most recent pattern of inflation is based on only two sets of measurements, and the tilt varies, with some smaller arrows pointing inward, so it is much less certain than the past patterns. Still, the radial pattern strongly suggests that inflation is occurring.

Figure 21. Rates of ground tilt measured in the summit region of Mauna Loa during 1975 to September 2002. Arrows point in the direction of downward tilt rate of the ground surface arrow lengths show the amount of tilt in microradians (note scale bars). A) inflation during 1975-1984, between the last two eruptions at Mauna Loa b) inflation after the 1984 eruption to 1993 c) deflation during 1993 to March (probably May) 2002 and d) a general return to inflation until at least September 2002. Courtesy HVO.

HVO's telemetered seismographic network recorded significant changes in seismicity before the Mauna Loa eruptions in 1975 and 1984 (figure 22). The short-term forecasts of these eruptions were based in large part on precursory activity. Both eruptions were preceded by an increase in earthquakes at intermediate depths NE of Moku`aweoweo, and then by an increase in shallower earthquakes beneath Mauna Loa's summit. From the 1984 eruption until late April 2002, approximately 30 earthquakes were located per year beneath Mauna Loa's summit and upper flanks. Rates of seismicity moderately increased beginning in late April 2002, particularly at depths greater than 15 km (figure 22d). As of 29 September 2002, 100 earthquakes were recorded in 2002 below the summit and upper flanks of the volcano, 83 of which occurred after mid-April. This rate is markedly higher than those of previous years, but it is still well below the rates seen prior to the last two eruptions. Before an eruption becomes imminent, HVO scientists expect that rates of shallow seismicity will elevate to levels much higher than those observed in late September 2002.

Figure 22. Monthly earthquakes (bars, scales at left) and cumulative numbers of located earthquakes (curves, scales at right), separated into three depth ranges, within or beneath Mauna Loa between 1974 and 29 September 2002. The earthquakes shown occurred beneath Mauna Loa's summit and upper flanks and had magnitudes greater than 1.0. Part "a" shows all earthquakes "b", shallow earthquakes (0 to 5 km deep) "c", intermediate earthquakes (5 to 15 km deep) and "d", deep earthquakes (greater than 15 km deep). Courtesy HVO.

References. Moore J G, Clague D A, Holcomb R T, Lipman P W, Normark W R, Torresan M E, 1989. Prodigous submarine landslides on the Hawaiian Ridge. J Geophys Res, 94: 17,465-17,484 Lockwood J P, Lipman P W, 1987. Holocene eruptive history of Mauna Loa volcano. U S Geol Surv Prof Pap, 1350: 509-535.

Information Contacts: Hawaiian Volcano Observatory (HVO) , U.S. Geological Survey, PO Box 51, Hawaii National Park, HI 96718, USA (URL: https://volcanoes.usgs.gov/observatories/hvo/).

September 2004 (BGVN 29:09) Cite this Report

Deep, long-period earthquake swarm and contraction in July and August 2004

After a swarm of deep earthquakes centered just S of Mauna Loa's summit caldera in late April 2002, seismicity remained barely elevated until July 2004. In other words, seismicity during late April 2002-July 2004 stood far lower than it did in the months prior to the 1975 and 1984 eruptions.

Starting in July 2004, a swarm of small (M < 3), deep (> 40 km), mostly long-period (LP) earthquakes occurred just S of the caldera and adjacent areas. Neither the depth nor the magnitude of the earthquakes changed significantly. Through 13 October 2004 more than 730 related earthquakes occurred beneath the summit caldera and the adjacent part of the SW rift zone.

The location and magnitude of earthquakes making up the recent swarm (seismicity from 24 April-15 October 2004, a 6-month interval) are shown in figure 23. Such a concentration of deep LP earthquakes from this part of Mauna Loa was unprecedented in the modern earthquake record dating back to the 1960s. In contrast, more typical seismicity over a 6-month period at Mauna Loa is shown in a figure in a previous issue ( BGVN 27:09). By comparison to the interval 24 April-15 October 2004, earthquakes in a typical 6 month interval are relatively sparse.

Figure 23. Seismicity for Mauna Loa for the 6-month period 24 April-15 October 2004. Courtesy of the U.S. Geological Survey, Hawaiian Volcano Observatory.

Inflation continued at the summit through the start of the earthquake swarm. In late August 2004, however, distances across the summit caldera began to contract significantly, apparently caused by the center of inflation shifting slightly to the S, rather than by deflation. This was the first contraction since inflation started in late April or early May 2002. Toward the end of September, the contraction ended and the line once again began to lengthen. During 2004, the inflation had been at a fairly steady to slightly increasing rate until the contraction in late August. When present, the lengthening, uplift, and tilting were taken to indicate swelling of the magma reservoir within the volcano.

Information Contacts: Hawaiian Volcano Observatory (HVO) , U.S. Geological Survey, PO Box 51, Hawaii National Park, HI 96718, USA (URL: https://volcanoes.usgs.gov/observatories/hvo/).

May 2012 (BGVN 37:05) Cite this Report

2004-2010 deformation trends intrusive bodies modeled

Mauna Loa has remained non-eruptive since April 1984. We previously reported on an April-October 2004, deep, long-period (LP) earthquake swarm and associated brief period of contraction ( BGVN 29:09). After that and through 2010, deformation continued at variable rates and with brief pauses. During 2004-2010, HVO reported little variation in gas emissions at Mauna Loa.

The material in this report is drawn from monitoring data collected by the USGS Hawaiian Volcano Observatory (HVO) and, in particular, Interferometric Synthetic Aperture Radar (InSAR) data provided by HVO's Mike Poland. A subsection below discusses the use of deformation data as a basis for modeling inferred magma bodies in the subsurface at Mauna Loa (Amelung and others, 2007).

Slowed edifice inflation. Increased rates of inflation following the April-October 2004 deep LP earthquake swarm continued through 2007, when HVO reported that GPS and InSAR-based inflation rates had slowed substantially. Comparison of radar interferograms covering two intervals (11 October 2003-19 November 2005 and 24 March 2007-17 April 2010) highlights the slowed deformation rates during the latter interval (figure 24). To better understand the technique used to observe the slowed rate of deformation at Mauna Loa, see the next section.

Figure 24. Radar interferograms of Mauna Loa covering the time intervals of (a) 11 October 2003-19 November 2005 and (b) 24 March 2007-17 April 2010. These interferograms highlight the slowing of inflation during the latter interval. The large number of color bands ('fringes') in (a) indicates an increased rate of inflation compared to the fewer number of fringes in (b). As depicted in the scale bar (bottom center), concentric and cyclical sets of fringes indicate a ground movement of 2.83 cm towards the satellite's line-of-sight during the time interval shown in each image. The images were produced from data acquired by the European Space Agency's Environmental Satellite (ENVISAT), with an incidence angle of 25° from the ground, looking W to E. Courtesy of Michael Poland, USGS-HVO.

InSAR technique to monitor deformation. A technique has emerged that enables scientists to create an image of where and how much displacement occurred over a ground or glacial (ice) surface (e.g., Rosen and others, 2000). The technique's spatial coverage is variable from hundreds of square meters to hundreds of square kilometers. Measurements of the component of deformation along the instrument's line-of-sight typically have centimeter-scale precision. While the precision may be less than some other deformation techniques (i.e., GPS monitoring or tilt measurements), the broad coverage can pinpoint particularly interesting patterns and help define areas for collateral studies, including further modeling of the causes of deformation (see next section).

The image, which is called a radar interferogram, compares two separate 'snapshots' acquired at distinct points in time. The snapshots are radar images of the topography of the ground surface in the area of interest (figure 25) acquired by an instrument mounted on an airplane or satellite. The images are generated by transmitting radar waves to the earth's surface the radar waves then reflect (backscatter) and are measured upon their return to the instrument. To make one interferogram, two such images taken at different times are compared. Variations in the phase of the coherent radar signal in the two snapshots disclose areas where displacement occurred along the instrument's line-of-sight (example radar waves A-E, figure 25). In some cases scientists collect and process enough data to enable them to make a time series of interferograms, for example, annual interferograms that enable yearly comparisons of the ground surface over a decade of time.

Figure 25. A cartoon representation of the basic principles of radar interferometry. As the satellite makes its first pass over a ground surface ('Initial ground surface'), it collects radar waves reflected off of the ground surface (solid wave, 'pass 1'). During a subsequent orbit (often months to years later), when the satellite again passes over the same ground surface, another collection is made from very nearly the same orbital location (dashed wave, 'pass 2'). If the ground surface deformed during the time between data collections (e.g., 'Subsided ground surface'), then the collected radar waves of the second pass will be out of phase compared to those collected during the first pass (example waves A-E, at right). The phase difference of the waves is then converted into the component of ground motion along the line-of-sight of the satellite (either towards or away from the satellite), and is represented by a color as part of a full color cycle. Since the technique is based on the phase difference of multiple waves, the accuracy is constrained by detectable fractions of the radar wave's wavelength. In figure 24, C-band radar (wavelength = 5.6 cm) was used. Image not drawn to scale. Image created by GVP staff.

On the interferograms, interference patterns appear as full color cycles, or 'fringes', indicating how far out of phase the radar waves are when they return to the satellite (figure 25) one fringe indicates a line-of-sight ground offset equivalent to one half of the radar waves' wavelength. An increased number of fringes at a specific area within an image thus indicates increased deformation during the time between images, allowing estimation of deformation rates over the time period analyzed. Our discussion of this technique has omitted various assumptions, sources of error, and corrections used to process and interpret the data.

Magma chamber and dike modeling . Amelung and others (2007) assessed measured ground deformation at Mauna Loa from InSAR data. They modeled the size, location, and geometry of inferred intrusive bodies beneath Mauna Loa that led to the observed surface deformation. Their modeling suggested a spherical magma chamber of 1.1 km radius, centered under the SE caldera margin at 4.7 km depth below the summit (0.5 km below sea level), and a vertical dike with most of its inflation occurring along an 8-km-long zone at depths of 4-8 km (Figure 26). The dike's direction of opening was normal to its inferred planar orientation. An HVO model, fit to ground-based GPS measurements, agrees with the model of Amelung and others (2007).

References. Amelung, F., Yun, S.H., Walter, T.R., Segall, P., and Kim, S.W. (2007) Stress Control of Deep Rift Intrusion at Mauna Loa Volcano, Hawaii. Science, 316 (5827), pg. 1026-1030 (DOI: 10.1126/science.1140035).

Rosen, P.A., Hensley, S., Joughin, I.R., Li, F.K., Madsen, S.N., Rodriguez, E., and Goldstein, R.M. (2000) Synthetic aperture radar interferometry, Proc. IEEE, 88, 333- 382.

Information Contacts: Michael Poland, Hawaiian Volcano Observatory (HVO) , U.S. Geological Survey, PO Box 51, Hawai'i National Park, HI 96718, USA (URL: https://volcanoes.usgs.gov/observatories/hvo/) Christelle Wauthier , Department of Terrestrial Magnetism, Carnegie Institute of Washington, Washington, DC.

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.

Synonyms
Cones
Craters
Basic Data

Last Known Eruption

Volcano Types
Rock Types
Tectonic Setting
Population
Geological Summary

Massive Mauna Loa shield volcano rises almost 9 km above the sea floor to form the world's largest active volcano. Flank eruptions are predominately from the lengthy NE and SW rift zones, and the summit is cut by the Mokuaweoweo caldera, which sits within an older and larger 6 x 8 km caldera. Two of the youngest large debris avalanches documented in Hawaii traveled nearly 100 km from Mauna Loa the second of the Alika avalanches was emplaced about 105,000 years ago (Moore et al. 1989). Almost 90% of the surface of the basaltic shield volcano is covered by lavas less than 4000 years old (Lockwood and Lipman, 1987). During a 750-year eruptive period beginning about 1500 years ago, a series of voluminous overflows from a summit lava lake covered about one fourth of the volcano's surface. The ensuing 750-year period, from shortly after the formation of Mokuaweoweo caldera until the present, saw an additional quarter of the volcano covered with lava flows predominately from summit and NW rift zone vents.

This volcano is located within the Hawaiian Islands, a UNESCO World Heritage property.

References

The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography.

Brigham W T, 1909. The volcanoes of Kilauea and Mauna Loa. Mem B P Bishop Museum, 2: 1-222.

Garcia M O, Davis M G, 2001. Submarine growth and internal structure of ocean island volcanoes based on submarine observations of Mauna Loa volcano, Hawaii. Geology, 29: 163-166.

Green J, Short N M, 1971. Volcanic Landforms and Surface Features: a Photographic Atlas and Glossary. New York: Springer-Verlag, 519 p.

Hitchcock C H, 1909. Hawaii and its Volcanoes. Honolulu: Hawaiian Gazette Pub Co, 306 p.

Jurado-Chichay Z, Rowland S K, 1995. Channel overflows of the Pohue Bay flow, Mauna Loa, Hawai'i: examples of the contrast between surface and interior lava. Bull Volcanol, 57: 117-126.

Jurado-Chichay Z, Rowland S K, Walker G P L, 1996. The formation of circular littoral cones from tube-fed pahoehoe, Mauna Loa, Hawai'i. Bull Volcanol, 57: 471-482.

Lipman P W, 1995. Declining growth of Mauna Loa during the last 10,000 years: rates of lava accumulation vs. gravitational subsidence. In: Rhodes J M, Lockwood J P (eds), Mauna Loa Revealed. Structure, Composition, History, and Hazards. Geophys Monogr, 92: 45-80.

Lockwood J P, Lipman P W, 1987. Holocene eruptive history of Mauna Loa volcano. U S Geol Surv Prof Pap, 1350: 509-535.

Macdonald G A, 1955. Hawaiian Islands. Catalog of Active Volcanoes of the World and Solfatara Fields, Rome: IAVCEI, 3: 1-37.

Moore J G, Clague D A, Holcomb R T, Lipman P W, Normark W R, Torresan M E, 1989. Prodigious submarine landslides on the Hawaiian Ridge. J. Geophys. Res, 94: 17,465-17,484.

Newhall C G, Dzurisin D, 1988. Historical unrest at large calderas of the world. U S Geol Surv Bull, 1855: 1108 p, 2 vol.

Riker J M, Cashman K V, Kauahikaua J P, Montierth C M, 2009. The length of channelized lava flows: Insight from the 1859 eruption of Mauna Loa volcano, Hawaii. J. Volcanol. Geotherm. Res., 183: 139-156.

Robinson J E, Eakins B W, 2006. Calculated volumes of individual shield volcanoes at the young end of the Hawaiian Ridge. J. Volcanol. Geotherm. Res., 151: 309-317.

Wanless V D, Garcia M O, Rhodes J M, Weis D, Norman M D, 2006. Shield-stage alkalic volcanism on Mauna Loa volcano, Hawaii. J. Volcanol. Geotherm. Res., 151: 141-155.

Yokose H, Lipman P W, 2004. Emplacement mechanisms of the South Kona slide complex, Hawaii Island: sampling and observations by remotely operated vehicle Kaiko. Bull Volcanol, 66: 569-584.

Zimbelman J R, Garry W B, Johnston A K, Williams S H, 2008. Emplacement of the 1907 Mauna Loa basalt flow as derived from precision topography and satellite imaging. J. Volcanol. Geotherm. Res., 177: 837-847.

Eruptive History

There is data available for 110 Holocene eruptive periods.

Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
1984 Mar 25 1984 Apr 15 Confirmed 0 Historical Observations Mokuaweoweo, SW and NE rift zones
1975 Jul 5 1975 Jul 6 Confirmed 0 Historical Observations Mokuaweoweo and NE and SW rift zones,
1950 Jun 1 1950 Jun 23 Confirmed 0 Historical Observations SW rift zone (2440 m)
1949 Jan 6 1949 May 31 Confirmed 0 Historical Observations Mokuaweoweo and SW rift zone
1942 Apr 26 1942 May 10 Confirmed 0 Historical Observations NE rift zone (2800 m) and Mokuaweoweo
1940 Apr 7 1940 Aug 18 Confirmed 0 Historical Observations Mokuaweoweo and SW rift zone
1935 Nov 21 1936 Jan 2 Confirmed 0 Historical Observations NE rift zone (3690 m) and Mokuaweoweo
1933 Dec 2 1933 Dec 18 Confirmed 0 Historical Observations Mokuaweoweo
1926 Apr 10 1926 Apr 28 (?) Confirmed 0 Historical Observations SW rift (2320 m)
1919 Sep 26 1919 Nov 5 (?) Confirmed 0 Historical Observations SW rift zone (3450 and 2350 m)
1916 May 19 1916 May 30 Confirmed 0 Historical Observations SW rift zone (3000 and 2250 m)
1914 Nov 25 1915 Jan 11 Confirmed 0 Historical Observations Mokuaweoweo
1907 Jan 9 1907 Jan 24 (in or after) Confirmed 0 Historical Observations SW rift zone (1890 m) and Mokuaweoweo
1903 Sep 1 1903 Dec 7 (?) Confirmed 0 Historical Observations Mokuaweoweo
1899 Jul 1 1899 Jul 23 Confirmed 1 Historical Observations NE rift zone (3260 m) and Mokuaweoweo
1896 Apr 21 1896 May 6 Confirmed 0 Historical Observations Mokuaweoweo
1892 Nov 30 1892 Dec 3 Confirmed 0 Historical Observations Mokuaweoweo
1887 Jan 16 1887 Jan 28 (?) Confirmed 0 Historical Observations SW rift zone (1740 m) and Mokuaweoweo
1880 Nov 5 1881 Aug 10 Confirmed 1 Historical Observations NE rift zone (3170 m)
1880 May 1 1880 May 6 Confirmed 1 Historical Observations Mokuaweoweo
1879 Mar 9 1879 Mar 9 (?) Confirmed 0 Historical Observations Mokuaweoweo
1877 Feb 14 1877 Feb 24 Confirmed 0 Historical Observations Mokuaweoweo, submarine west flank
1876 Feb 13 1876 Feb 14 (?) Confirmed 0 Historical Observations Mokuaweoweo
1875 Aug 11 1875 Aug 18 (?) Confirmed 0 Historical Observations Mokuaweoweo
1875 Jan 10 1875 Feb 9 (?) Confirmed 0 Historical Observations Mokuaweoweo
1873 Apr 20 1874 Oct 19 (?) Confirmed 1 Historical Observations Mokuaweoweo
1873 Jan 6 1873 Jan 7 (?) Confirmed 0 Historical Observations Mokuaweoweo
1872 Aug 9 1872 Sep Confirmed 1 Historical Observations Mokuaweoweo
1871 Aug 10 1871 Aug 30 (?) Confirmed 0 Historical Observations Mokuaweoweo
[ 1870 Jan 1 (?) ] [ 1870 Jan 15 (?) ] Uncertain 0 Mokuaweoweo
1868 Mar 27 1868 Apr 22 Confirmed 2 Historical Observations SW rift zone (1000 m) and Mokuaweoweo
1865 Dec 30 1866 Apr 29 (?) Confirmed 0 Historical Observations Mokuaweoweo
1859 Jan 23 1859 Nov 25 Confirmed 1 Historical Observations North flank (2800 m) and Mokuaweoweo
1855 Aug 11 1856 Nov Confirmed 1 Historical Observations NE rift zone (3200 m) and Mokuaweoweo
1852 Feb 17 1852 Mar 11 (?) Confirmed 2 Historical Observations NE rift zone (2560 m) and Mokuaweoweo
1851 Aug 8 1851 Aug 11 ± 1 days Confirmed 0 Historical Observations Mokuaweoweo and SW rift zone
1849 May Unknown Confirmed 0 Historical Observations Mokuaweoweo
1843 Jan 9 1843 Apr 10 (?) Confirmed 0 Historical Observations North flank, Mokuaweoweo and NE rift
1832 Jun 20 1832 Jul 15 ± 7 days Confirmed 0 Historical Observations Mokuaweoweo and adjacent vents
1750 (?) Unknown Confirmed 0 Historical Observations North flank (2380 m) and SW rift zone?
1730 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
1685 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
1680 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NW flank
1650 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
1640 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
1540 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
1510 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
1500 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
1470 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
1440 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone and NW flank
1390 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
1370 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone and Mokuaweoweo
1360 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
1310 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) SW rift zone
1190 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone and Mokuaweoweo
1170 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
1130 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) SW rift zone
1070 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
1040 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
0940 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
0830 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) Mokuaweoweo and NW flank
0810 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) Mokuaweoweo
0680 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) Mokuaweoweo
0630 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
0600 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) Mokuaweoweo
0550 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) Mokuaweoweo
0480 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) Mokuaweoweo
0450 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
0350 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) Mokuaweoweo
0300 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
0200 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) Mokuaweoweo
0150 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) SE rift zone
0100 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) SE rift zone
0050 (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
0030 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE and SW rift zones
0060 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) Mokuaweoweo
0080 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) SE rift zone
0200 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
0300 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
0400 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) SW rift zone
0500 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) SW rift zone
0600 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
0950 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) Mokuaweoweo
1300 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) Mokuaweoweo and NE rift zone
1650 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE and SW rift zones
1700 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) SW rift zone
1750 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
1800 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NW and SW rift zones
1900 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) SW rift zone
2000 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) SW rift zone
2050 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) Mokuaweoweo
2150 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
2250 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
2350 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) Mokuaweoweo
2750 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE and SW rift zones
3250 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) SW rift zone
3350 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
3750 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
4250 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) SW rift zone
5350 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) SW rift zone
5650 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) SW rift zone
5850 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE and SW rift zones
6250 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
6550 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) Mokuaweoweo
6650 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
7150 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE and SW rift zones
7350 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) SW rift zone
7550 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
7850 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone
8050 BCE (?) Unknown Confirmed 0 Radiocarbon (uncorrected) NE rift zone

Deformation History

There is data available for 2 deformation periods. Expand each entry for additional details.

Deformation during 2006 Oct 15 - 2006 Oct 15 [Subsidence Observed by InSAR]

Remarks: Two earthquakes triggered subsidence of lava deposits on Hawaii.

ENVISAT ASAR mode 4, track 157, interferogram spanning 17 February?29 December 2006 and indicating deformation associated with the 15 October 2006 Hawai?i earthquakes. The lava flows discussed in the text are outlined and labeled. The dashed boxes delimit areas covered in Figures 4?6, and the gray box outlines the area of Figure 7. The fringes at the summit of Mauna Loa indicate long-term volcano inflation (confirmed by GPS measurements) and are not related to the 15 October 2006 earthquakes. The inset shows the location of the K?holo Bay (Mw 6:7) and Mahukona (Mw 6:0) earthquakes, with locations and focal mechanisms from the Global Centroid Moment Tensor catalog (see the Data and Resources section).

Reference List: Poland 2010.

Full References:

Poland, M., 2010. Localized surface disruptions observed by InSAR during strong earthquakes in Java and Hawai'i. Bulletin of the Seismological Society of America, 100(2), 532-540.

Deformation during 2002 - 2005 [Variable (uplift / subsidence) Observed by InSAR]

Remarks: InSAR shows inflation of a dike-like magma body in the southwest rift zone between 2002 and 2005.

(A) Averaged 2002 to 2005 satellite radar interferogram of the Big Island of Hawaii showing ground velocity in the radar line-of-sight (LOS) direction. The radar looks toward the east (ascending orbit) with an incidence angle of

45? on the ground (Standard Beam A6). The star denotes the 1983 Kaoiki earthquake. The seismicity with depth > 20 km and with M > 2.2 is also shown. (B) Vertical and east component of the ground-velocity field obtained by combining averaged interferograms from four different viewing geometries. The black line and circle indicate the dike and magma chamber, respectively, of the model in Fig. 2A.

Reference List: Amelung et al. 2007.

Full References:

Amelung F, Yun S H, Walter T R, Segall P, Kim S W, 2007. Stress control of deep rift intrusion at Mauna Loa volcano, Hawaii. Science, 316, 1026-1030. https://doi.org/10.1126/science.1140035

Emission History

There is data available for 1 emission periods. Expand each entry for additional details.

Emissions during 1984 Mar 25 - 1984 Mar 25 [1197 kt SO2 at 11 km altitude]

Start Date: 1984 Mar 25 Stop Date: 1984 Mar 25 Method: Satellite (Nimbus-7 TOMS)
SO2 Altitude Min: 11 km SO2 Altitude Max: 11 km Total SO2 Mass: 1197 kt

Date Start Date End Assumed SO2 Altitude SO2 Algorithm SO2 Mass
19840325 11.0 1197.000

Photo Gallery
GVP Map Holdings

The maps shown below have been scanned from the GVP map archives and include the volcano on this page. Clicking on the small images will load the full 300 dpi map. Very small-scale maps (such as world maps) are not included. The maps database originated over 30 years ago, but was only recently updated and connected to our main database. We welcome users to tell us if they see incorrect information or other problems with the maps please use the Contact GVP link at the bottom of the page to send us email.


Title: Hawaii
Publisher: US Geological Survey
Country: United States
Year: 1988
Map Type: Topographic
Scale: 1:750,000

Title: Seismicity of Hawaii
Publisher: US Geological Survey
Country: United States
Year: 1988
Map Type: Topographic
Scale: 1:750,000

Title: Map Showing Distribution, Composition, and Age of Late Cenozoic Volcanic Craters in Hawaii
Publisher: US Geological Survey
Country: United States
Year: 1988
Series: Misc Investigations
Map Type: Geology
Scale: 1:1,000,000

Title: HI-Map of Dist, Comp & Age of Late CZ Volc Centers
Publisher: US Geological Survey
Country: United States
Year: 1988
Series: MI
Map Type: Geology (Volcano)
Scale: 1:1,000,000

Title: Seismicity of Hawaii, 1962-1985
Publisher: US Geological Survey
Country: United States
Year: 1988
Series: OFR
Map Type: Geophysical (Seismic)
Scale: 1:750,000

Title: Hawaiian Islands
Publisher: DMA Aerospace Center
Country: United States
Year: 1986
Series: ONC
Map Type: Topographic
Scale: 1:1,000,000

Title: Aeromag Map of Rift Systems of Kilauea, Mauna Loa
Publisher: US Geological Survey
Country: United States
Year: 1986
Series: MFS
Map Type: Unknown
Scale: 1:100,000

Title: Apparent-Resistivity Map of Kilauea, Mauna Loa
Publisher: US Geological Survey
Country: United States
Year: 1986
Series: MFS
Map Type: Unknown
Scale: 1:100,000

Title: Earthquake Map of South Hawaii, 1968-1981
Publisher: US Geological Survey
Country: United States
Year: 1985
Series: MI
Map Type: Geophysical (Seismic)
Scale: 1:100,000

Title: Hawaii to French Frigate Shoals
Publisher: US Department of Commerce, NOAA National Ocean Service
Country: United States
Year: 1983
Map Type: Bathymetric
Scale: 1:1,650,000

Title: Geothermal Resources of Hawaii
Publisher: HI Institute of Geophysics, Univ. HI
Country: United States
Year: 1983
Map Type: Unknown
Scale: 1:500,000

Title: Oblique Map of Loihi Seamount, Papa'u Landslide
Publisher: US Geological Survey
Country: United States
Year: 1982
Series: OFR
Map Type: Physiographic
Scale: 1:100,000

Title: Close-Up USA Hawaii
Publisher: National Geographic Society
Country: United States
Year: 1976
Map Type: Geology
Scale: 1:675,000

Title: Hawaii
Publisher: US Geological Survey
Country: United States
Year: 1975
Series: W532
Map Type: Topographic
Scale: 1:250,000

Title: Island of Hawaii
Publisher: Dept of Commerce, ESSA, Coast & Geodetic Survey
Country: United States
Year: 1967
Map Type: Bathymetric
Scale: 1:250,000

Title: Hawaii South
Publisher: US Army Map Service
Country: United States
Year: 1962
Map Type: Topographic
Scale: 1:250,000

Smithsonian Sample Collections Database

The following 331 samples associated with this volcano can be found in the Smithsonian's NMNH Department of Mineral Sciences collections, and may be availble for research (contact the Rock and Ore Collections Manager). Catalog number links will open a window with more information.


Earth's Largest Volcano, Hawaii's Mauna Loa

Mauna Loa was observed by a team of experts from the Rosenstiel School of Marine and Atmospheric Science at the University of Miami (MU). The tests were accomplished using the Interferometric Synthetic Aperture Radar (InSAR) satellite imagery that receives and interprets data from ground movements.

Through the InSAR technology, researchers found the exact parameters of the magma's direction and change over time. And with the help of the Hawaii Volcano Observatory, they were also able to analyze the mapping of the flanks that moved using GPS networks.

In reference to the research published in Scientific Reports entitled "Southward growth of Mauna Loa's dike-like magma body driven by topographic stress," the scientists found that a large volume of magma moved into a basin located on the summit caldera's southern area between the year 2015 to 2020. This basin is a dike-like contraption with a depth of 3 kilometers just below the summit.


Hawaii's Mauna Loa volcano is beginning to stir, new data reveal

Mauna Loa -- Hawaii's biggest and potentially most destructive volcano -- is showing signs of life again nearly two decades after its last eruption.

Mauna Loa volcano last erupted on March 25, 1984. The next day, massive lava fountains erupted on the volcano&rsquos northeast rift zone about 11 miles from the original outbreak point. Photo: USGS HVO

Recent geophysical data collected on the surface of the 13,500-foot volcano revealed that Mauna Loa's summit caldera has begun to swell and stretch at a rate of 2 to 2.5 inches a year, according to scientists from the U.S. Geological Survey (USGS) and Stanford University. Surface inflation can be a precursor of a volcanic eruption, the scientists warn.

"Inflation means that magma is accumulating below the surface, but at this point we don't have the kinds of sophisticated models that would be required to tell us if or when an eruption will occur," said Paul Segall, a professor of geophysics at Stanford who has collaborated with USGS volcanologists in Hawaii since 1990.

Located on the Big Island of Hawaii, Mauna Loa -- or "Long Mountain" in Hawaiian -- is the largest volcano in the world. Its last eruption occurred in spring 1984 -- a violent three-week event that produced fast-moving lava flows that came within 4 miles of the city of Hilo. The volcano has remained silent for the past 18 years -- in sharp contrast to its neighbor, Kilauea, which has been erupting continuously since January 1983.

Oblique shaded-relief map of the five volcanoes that built the Island of Hawai`i. Mauna Loa encompasses 51 percent of the island's surface area its most recent eruption was in 1984. Map: USGS HVO

"After the 1984 eruption, Mauna Loa went through nearly a decade of inflation, followed by almost 10 years of deflation," said Peter Cervelli, a geophysicist with the Hawaiian Volcano Observatory (HVO).

The deflationary period abruptly ended around Mother's Day, May 12, when HVO's global positioning system (GPS) network revealed that the summit had begun to rise and swell. May 12 was the same day that Kilauea's most recent active lava flow began -- a discovery that scientists say is far from coincidental.

"This clearly indicates that there is a connection between the two magma systems," Segall noted. "That's the great thing about Hawaii: It's so incredibly active that just about every year we learn something new."

HVO maintains several GPS stations on Mauna Loa that continuously record their positions using information transmitted from orbiting satellites. The around-the-clock satellite data allow scientists to measure how far the GPS stations have moved -- and thus determine if the volcano is expanding or contracting. Cervelli, who earned his doctorate at Stanford last year, said the university has loaned HVO eight additional GPS stations to monitor the volcano. Because of the remote mountaintop location, each instrument can cost up to $20,000 to install. Segall's research on the Big Island is funded through a National Science Foundation grant.

This satellite GPS station on Kilauea volcano is one of eight Stanford instruments being deployed by USGS for service on 13,500-foot Mauna Loa. To reach the summit, David Okita and other USGS contract pilots must transport each station by helicopter -- a costly and somewhat risky procedure. Photo: Peter Cervelli/USGS HVO

"Until recently, Stanford's research in Hawaii has been primarily on Kilauea, but when Mauna Loa started to show renewed activity in late spring, Paul [Segall] agreed to lend us four of his continuous GPS receivers," Cervelli explained. "We are holding four more Stanford instruments in reserve to be deployed as conditions warrant."

Cervelli and his USGS colleagues will work with Segall to interpret the new GPS data as they become available.

"We see this as an opportunity to watch the volcano evolve through an entire eruptive period -- from early awakening to actual eruption," Cervelli said. "If the recent activity does culminate in an eruption, this will be the first time that a Mauna Loa eruption is imaged with precise clarity. Without Stanford's help, this would not be possible."

History of destruction

Mauna Loa has erupted 33 times since 1843, spewing out enough lava to cover 40 percent of the Big Island. The most destructive eruption in recorded history occurred in 1950, when lava raced to the sea at speeds up to 5 miles an hour -- destroying homes, businesses, roads and ranches along the way.

Despite the volcano's destructive potential, the USGS estimates that more than $2.3 billion has been invested in new construction along Mauna Loa's slopes since the 1984 eruption.

"Mauna Loa is capable of erupting huge volumes of lava in a relatively short period of time, and the flows can reach great distances," Segall observed. "It presents a more significant safety hazard than Kilauea."

Cervelli echoed that concern: "There has been a substantial amount of development on what has historically been the most hazardous part of Mauna Loa -- its southwest rift zone above South Point. Though lava flows can reach Hilo on the eastern side of the island and the Gold Coast resorts of Kona in the west, flows are much more likely to inundate the subdivisions in the southwest rift zone -- and possibly without much warning."

Increased earthquake activity is another indication that magma is rising to the surface. "Seismicity does seem to be picking up," Cervelli noted, "but at this point we are not issuing a public warning. Instead, we are asking that the people of Hawaii remind themselves that they live among the world's most active volcanoes."

© Stanford University . All Rights Reserved. Stanford , CA 94305 . (650) 723-2300 .


Mauna Loa SP-28 - History

by Zahra Hirji Thursday, August 7, 2014

Earth&rsquos largest active volcano is taking a nap. And after 30 years, no one is quite sure when Hawaii&rsquos Mauna Loa will reawaken. Odds are that it will be within the next couple of decades — and that it will be spectacular.

Red hot lava will fountain violently, reaching 50 meters into the air. An underground molten magma ocean will be unleashed, draining from giant fresh cracks in the surface. A plume of sulfur-rich steam and ash will climb into the sky, billowing like a huge smoke stack.

It paints a hellish scene, but is there any danger for humans? That depends on whether the eruptions are confined to the mountain&rsquos highest levels above the tree line, or if, as scientists and emergency managers fear, the flows and plumes migrate downslope to the realm of people and commerce.

When Mauna Loa last erupted in 1984 (left), lava came within 7 kilometers of Hilo (right). Parts of Hilo are built on lava from eruptions that occurred over the past couple of hundred years. Credit: left: U.S. Geological Survey Hawaiian Volcano Observatory/ESW Image Bank right: ©Ken Lund, CC BY-NC-ND 2.0.

History warns us that Mauna Loa&rsquos current silence is anomalous. Over the past 3,000 years, the geologic record testifies that the volcano has, on average, erupted every six years. And about 45 percent of historical eruption sites have departed the volcano&rsquos summit for lower elevations.

Lying at the foot of the mountain&rsquos northeastern side is the Big Island&rsquos largest city, Hilo. Despite being the population most recently threatened by Mauna Loa (when the volcano last erupted in 1984), Hilo residents are largely apathetic to their risk, according to Frank Trusdell, a geologist at the U.S. Geological Survey&rsquos (USGS) Hawaiian Volcano Observatory (HVO) and the world&rsquos leading Mauna Loa expert. Part of the problem is the city&rsquos growing population, which has increased by almost a third since the last eruption, from about 35,000 to more than 43,000. In response, development has pushed farther up Mauna Loa&rsquos slopes.

Mauna Loa lava flows can be seen on the Big Island, including crossing the major highways 11 and 190. The dark lava flow shown at left in this photo formed in 1859 and the dark flow shown at right is from about 1800. Credit: USDA Forest Service.

The last Mauna Loa eruption to threaten communities on the volcano&rsquos southwestern side was in 1950. Since that eruption, several subdivisions have sprung up, including one of the state&rsquos largest, Hawaiian Ocean View Estates, and the population has climbed from 8,000 to more than 18,000. &ldquoA lot of new people have come in not realizing they are settling on an active volcano,&rdquo says Jim Kauahikaua, head of HVO. According to a survey conducted in 2003, less than 25 percent of Big Island residents living on the west and southwest coasts knew that Mauna Loa had erupted in the previous 50 years.

The passage of time has also left a shortage of firsthand experience among those tasked with responding to the eruption. When asked how many geologists currently working at HVO were around for the previous eruption, Trusdell gives a sobering response: &ldquoone,&rdquo himself. The statistics are even bleaker at Hawaii&rsquos state Civil Defense Agency, the group in charge of emergency management, where there is no overlap.

Meanwhile, the risk of a future catastrophic Mauna Loa eruption grows as more people and buildings pack into known hazardous areas like Hilo and Hawaiian Ocean View Estates. And that&rsquos why, despite Mauna Loa&rsquos current silence, HVO geologists are already taking steps — upgrading their monitoring tools and talking with the public — to prepare Hawaii for another eruption.

Location, Location, Location

Erupting vents on Mauna Loa's northeast rift zone near Pu‘u‘ula‘ula on March 25, 1984, sent massive 'a'a lava flows down a rift toward Kūlani. Credit: U.S. Geological Survey Hawaiian Volcano Observatory.

Mauna Loa may share an island with four other volcanoes — and it even shares the same general magma source, a hot spot currently positioned below the island — but its potential scope of destruction is unmatched.

The massive shield volcano, with active zones that sprawl 60 kilometers from the summit to the southeast and about 20 kilometers to the northeast, sits in the middle of the island. The other big topographic bumps are all relegated to outer vantages — the dormant Kohala to the northwest and Mauna Kea to the northeast, the active Hualalai to the west, and the currently erupting Kilauea to the southeast. No other volcano poses a threat to both the eastern and western sides of the island.

Part of the difficulty planning for a future eruption is anticipating where it will occur. Even after an eruption has started, it might not be so obvious. The 1984 event is proof of that.

The eruption started early in the morning on Sunday, March 25, 1984, with lava flows in Moku΄āweoweo caldera, the summit crater. A few hours later, eruptive fissures migrated southwest about 5 kilometers, reaching down to an elevation of 3,886 meters before the lava retreated to the 4,170-meter summit.

By late morning, however, new fissures had formed along the volcano&rsquos northeastern side. A 2-kilometer-long &ldquocurtain&rdquo of lava fountained from the cracks, reaching up to 50 meters in height and releasing between 1 million and 2 million cubic meters of lava per hour.

Over the 22-day eruption, new fissures propagated farther down the mountainside, prompting several families living in Hilo&rsquos upper reaches to voluntarily evacuate. Along the steepest slopes, lava oozed at speeds up to 0.2 kilometers per hour. The eruption produced seven distinct flows, the longest of which traveled more than 20 kilometers.

Damage due to the eruption was limited to some roads and power lines that were overrun by lava. The flows stopped 7 kilometers short of Hilo, but still threatened the only cross-island highway, Saddle Road, as well as a prison. Civil Defense closed the highway for the duration of the eruption as a precaution.

A geologist monitors the 1984 Mauna Loa eruption. Credit: Christina A. Neal, U.S. Geological Survey.

When the lava began flowing, Frank Trusdell was on Oahu working on a graduate degree in plant pathology. Trusdell, who had spent many summers working at HVO during and after college, called up his former boss, Reginald Okamura, to check in and was given a curt order: &ldquoGet over here.&rdquo Trusdell was on Mauna Loa two days later.

Jack Lockwood, now a consulting geologist, was the Mauna Loa geologist at the time of the eruption. &ldquoFor the first week, we were concerned about Hilo,&rdquo Lockwood says. That is when the flows were dynamic and fast-paced. Due to Mauna Loa&rsquos varied topography, the downslope lava switched composition from speedy lava, called `a`a (pronounced ah-ah), on the upper, steeper slopes to a slower-moving ropy form, called pahoehoe (pronounced pa-hoy-hoy), on the lower, flatter regions.

&ldquoSeeing how quickly lava moves, whether it is `a`a or the pahoehoe, makes me a believer that if you are not paying attention, you could die working around [the lava] when you are out on the flow fields,&rdquo Trusdell says. &ldquoThere&rsquos no latitude for error.&rdquo

For safety reasons, and to keep pace with the flows, monitoring was mostly done by helicopter or plane. Trusdell mapped the flows from aloft by sketching their margins in pencil on a topographic map.

After the eruption ended, Trusdell returned to school, switched to volcanology and eventually joined HVO as a temporary hire before taking over for Lockwood as Mauna Loa geologist in 1996.

Monitoring the Sleeping Giant

In the event of a future eruption, geologists and emergency managers will work together to assess and respond to the threat in much the same way they did back in 1984.

The region around the eruption will be closed off to the public and air space will be restricted to those involved with the response. Civil Defense will handle road closures and evacuations using information about lava flow intensity and di"ection provided by the HVO geologists.

Currently, Trusdell is the only full-time HVO staffer devoted to Mauna Loa. That will change as soon as the volcano starts to show signs of restlessness, he says. By the time an eruption actually starts, the observatory will be manned 24/7 &ldquoso that somebody&rsquos looking at all the data, all the time,&rdquo Kauahikaua says, which will require bringing in staff from USGS sister volcano observatories in Alaska, California and Washington.

Unlike in 1984, when there was only one seismometer used to measure earthquakes near Mauna Loa&rsquos summit — and it was turned off the night of the eruption — scientists today have more and better monitoring tools collecting data all day and night."

Trusdell and the other HVO geologists collect data from nearly 50 instruments speckled across Mauna Loa. Seismometers record earthquake activity at more than 15 different locations. Nearly a dozen tiltmeters measure how much the ground inflates, or &ldquotilts,&rdquo due to the volcano&rsquos internal accumulation of lava. Two shoebox-sized cameras are positioned along a section of the volcano&rsquos most recent areas of activity, offering continuous real-time views of the summit crater and the upper northeast rift zone. And more than 20 GPS devices connect to satellite systems and provide geologists with precise indications of motion, accurate down to a few millimeters, which are used for map-making.

HVO geologists collect data from nearly 50 instruments — everything from seismometers to tiltmeters to thermal cameras — speckled across Mauna Loa. Credit: all: Patrick et al., Journal of Applied Volcanology (2014).

Then there are the alarms. For example, a Mauna Loa summit seismometer may trigger if more than four earthquakes occ"r in an hour, and then an alert is sent directly to the HVO geologists' cellphones and email. Likewise, th"rmal cameras measure ground surface temperatures and send alerts if the temperature observed passes a certain level tiltmeters also send alerts if the ground inflates rapidly within a short time.

The observatory&rsquos alarm system is flexible, says HVO geophysicist Weston Thelen. &ldquoThresholds now will likely be too sensitive once activity ramps up,&rdquo he says. As future activity unfol"s, &ldquowe may develop new alarms … we need to be ready to move quickly to address needs as they occur.&rdquo

&ldquolong with technological advances, scientists are now much better informed about Mauna Loa&rsquos long eruptive history, courtesy of years of intensive fieldwork and mapping. The widespread and detailed mapping of Mauna Loa &ldquois unprecedented for any other volcano in the world,&rdquo Trusdell says. That&rsquos because of the volcano&rsquos massive size: It is almost as big as the rest of the Hawaiian Islands put together. With clues from the giant volcano&rsquos eruptive history, he has been working to simulate what future eruptions may look like.

&ldquoTo evaluate risk, to evaluate the future, you have to know the past,&rdquo Lockwood says.

The Past Is Key to the Future

On June 1, 1950, at 9:04 p.m., Mauna Loa started quaking. Less than 30 minutes later, Mauna Loa's upper southwestern flank (higher than 2,400 meters elevation) glowed. Credit: Gordon A. Macdonald, U.S. Geological Survey.

In the past 200 years, just one eruption, in 1880, has sent lava into Hilo&rsquos current city limits. Based on mapping of old flows, it appears that the lava stopped about 1.5 kilometers short of the old city limits. But because the city has grown since then, the old flows are now partially covered with houses, parks and roads.

Trusdell used a prehistoric flow similar to the 1880 eruption as the basis of his representative worst-case scenario for Hilo. To determine the impacts of such an eruption occurring today, he first accumulated infrastructure and tax data, including identifying the city&rsquos critical infrastructure — airports, bridges, police stations, electrical power plants and nursing homes — and its monetary value. Trusdell only accounted for land improvements (anything built on top of the land), not the value of the land itself. He also calculated a cost per mile of road.

If we take the historical lava flow and apply these modern parameters, Trusdell says, then we can start to assess what could happen. The results are grim: The eruption could cause approximately $1.2 billion in damage. And &ldquothis estimate is conservative,&rdquo he adds.

For an eruption heading for Hilo, there is a silver lining, however: Lava flows would likely take weeks if not months to reach the city, giving residents ample time to pack up and leave.

But this is not true of all Mauna Loa eruptions. If an eruption in the summer of 1950 is any indication, people on the southwest side of the island would have far less time to respond — on the order of hours to days.

On June 1, 1950, at 9:04 p.m., the massive mountain started quaking. Less than 30 minutes later, Mauna Loa&rsquos upper southwestern flank glowed fire-engine red. The brief time between the first tremor and the appearance of lava presaged the heart-racing pace of the eruption.

Several flows, or lava &ldquofingers,&rdquo stretched down the mountainside that night, one a raging river of lava that crossed the region&rsquos only exit route, Highway 11. The burning asphalt released clouds of noxious black smoke. The flow then consumed a post office, multiple houses and a gas station before emptying into the ocean. The flow took only 3.5 hours to reach the ocean, one of the fastest times ever recorded for flows traveling more than 30 kilometers. A combination of high lava output and, more importantly, steep slopes contributed to the speed of the lava flow, which reached about 10 kilometers per hour.

By the end of the eruption on June 23, 1950, Mauna Loa had produced eight discrete flows and enough lava to fill the Empire State Building more than 358 times. Disruptions to daily life continued well after the eruption&rsquos end. Transportation to and from many homes and farms was cut off by flows, and it took weeks for the lava to cool enough for new roads to be paved. And they did get paved, and new roads, buildings and infrastructure were built.

Expanding Into Danger Zones

Today, the southwestern stretch of Highway 11 is lined with real estate signs, from the western town of Kailua-Kona down to the Hawaiian Ocean View Estates subdivision, which is built atop fissures dating to an 1887 eruption. And the real estate market is growing, despite the risks. &ldquoccording to Arnold Rabin, a Big Island real estate agent for 36 years, prospective buyers show a range of concern about the volcano some care a lot and others not at all.

&ldquoI don&rsquot think many people think of it in their day-to-day existence,&rdquo he says. Personally, he adds, &ldquoI choose to live here. The pros far outweigh the cons.&rdquo

In general, realtors refer people to the HVO website, which displays a map of volcanic hazard zones (or lava zones) on the Big Island — ranked one through nine, with zone one the most dangerous — or to a 1997 USGS handbook titled &ldquoVolcanic and Seismic Hazards on the Island of Hawaii,&rdquo which covers volcano, earthquake and tsunami threats.

HVO researchers have created a map of volcanic hazard zones on the Big Island — ranked one through nine, with zone one being the most dangerous. Credit: U.S. Geological Survey Hawaiian Volcano Observatory.

Prospective buyers are made to sign the Hawaii Island Disclosure, a two-page document out"ining aspects of property ownership particular to the island, before a purchase goes through. But even in that, mention of volcanoes is buried in a paragraph sandwiched between property taxes and wastewater disposal. The disclosure notes that volcanoes &ldquomay affect the availability, limits and cost of property and/or liability insurance.&rdquo The translation, Rabin says, is that banks and insurance companies steer clear of the most hazardous zone one, and sometimes lava zone two, offering no loans, mortgages, or insurance coverage to people living there.

But where private companies don&rsquot offer coverage, the state fills the gap. Starting in 1992, the government created the controversial Hawaii Property Insurance Association (HPIA), which offers insurance to residents in the riskiest parts of the island, including the southwest rift zone. In 2013, HPIA had more than 2,190 policyholders in the state of Hawaii, and 40 percent of them were in the Big Island&rsquos lava zone two.

According to a 2008 article in the Honolulu Advertiser, &ldquothe state-created HPIA has made rapid development possible in precisely those areas of the Big Island most likely to be devastated by lava flows from the Kilauea volcano, or from future eruptions of Mauna Loa volcano.&rdquo

No Sneak Attacks

Remnants of Mauna Loa's eruptive history dot the landscape. Credit: ©Brocken Inaglory, CC BY-SA 3.0.

Volcanoes rarely blow without warning. Eruptions are preceded by many subtle signs in the form of cracks, bulges, quakes and steam. In the case of Mauna Loa, geologists say they will likely have several months to a couple of years to prepare. However, whether that&rsquos enough time to prepare the general public is not a gamble that Trusdell says geologists are willing to make.

Every January for the past five years, HVO has hosted a public outreach event: Volcano Awareness Month. Geologists give talks about the island&rsquos various volcanoes and their respective hazards, both within the national park and in towns across the island. Trusdell&rsquos annual speech is titled, &ldquoMauna Loa: How Well Do You Know the Volcano in Your Backyard?&rdquo

&ldquoPeople should be aware of where the hazards are,&rdquo Trusdell says. And if you&rsquore in the hazard zone, &ldquoyou can reduce your personal risk by being prepared.&rdquo Stock an emergency kit with food, medicine and clothes keep copies of medical and financial papers and devise plans to connect with family and/or friends during an emergency.

Conversations regarding Mauna Loa among scientists, officials and the public are focused on reacting — laying out plans for what the geologists, disaster managers or individuals will do when an eruption starts. For the Mauna Loa hazard to feel real, Trusdell says, Hawaii residents need a more frequent reminder of Mauna Loa&rsquos hazard than his annual talk. That&rsquos why HVO shares information about changes in the volcano&rsquos physical condition whenever something is detected, no matter how small.

Recently, there has been a change — an uptick in earthquake swarms measured around the volcano. Although &ldquothis is definitely a change,&rdquo Kauahikaua says, it doesn&rsquot necessarily mean that a new eruption is brewing. For an eruption, &ldquowe&rsquod be looking for a lot more signs&rdquo and a lone earthquake swarm &ldquois only one factor — and it&rsquos a weak one at this point,&rdquo he says.

At the very least, however, the earthquake swarms are a reminder of Mauna Loa&rsquos continued active status. &ldquoIt&rsquos not a dead volcano yet,&rdquo Trusdell says.

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