Misplaced Pages

Revision as of 15:28, 8 January 2013

Mauna Loa
Mauna Loa as seen from the air; Hualālai is visible in the background
Highest point
Elevation	13,679 ft (4,169 m)
Prominence	7,079 ft (2,158 m)
Listing	Ultra
Geography
Mauna LoaHawaii, USA
Parent range	Hawaiian Islands
Topo map	USGS Mauna Loa
Geology
Rock age	700,000–1 million
Mountain type	Shield volcano
Volcanic arc/belt	Hawaiian-Emperor seamount chain
Last eruption	1984
Climbing
First ascent	1794

Mauna Loa (/ˌmɔːnə ˈloʊ.ə/ or /ˌmaʊnə ˈloʊ.ə/; Hawaiian: [ˈmɔunə ˈlowə]) is one of five volcanoes that form the Island of Hawaii in the U.S. state of Hawaiʻi in the Pacific Ocean, and the largest on Earth in terms of volume and area covered. It is an active shield volcano, with a volume estimated at approximately 18,000 cubic miles (75,000 km), although its peak is about 120 feet (37 m) lower than that of its neighbor, Mauna Kea. The Hawaiian name "Mauna Loa" means "Long Mountain". Lava eruptions from Mauna Loa are silica-poor, and very fluid; eruptions tend to be non-explosive and the volcano has relatively shallow slopes.

Mauna Loa has probably been erupting for at least 700,000 years, and may have emerged above sea level about 400,000 years ago. The oldest-known dated rocks are not older than 200,000 years. The volcano's magma comes from the Hawaii hotspot, which has been responsible for the creation of the Hawaiian island chain over tens of millions of years. The slow drift of the Pacific Plate will eventually carry Mauna Loa away from the hotspot within 500,000 to one million years from now, at which point it will become extinct.

Mauna Loa's most recent eruption occurred from March 24 to April 15, 1984. No recent eruptions of the volcano have caused fatalities, but eruptions in 1926 and 1950 destroyed villages, and the city of Hilo is partly built on lava flows from the late 19th century. In view of the hazards it poses to population centers, Mauna Loa is part of the Decade Volcanoes program, which encourages studies of the most dangerous volcanoes. Mauna Loa has been monitored intensively by the Hawaiian Volcano Observatory since 1912. Observations of the atmosphere are undertaken at the Mauna Loa Observatory, and of the Sun at the Mauna Loa Solar Observatory, both located near its summit. Hawaii Volcanoes National Park covers the summit and the southeastern flank of the volcano, also incorporating a separate volcano, Kīlauea.

Geology

Setting

Like all Hawaiian volcanoes, Mauna Loa was created as the Pacific tectonic plate moved over the Hawaiian hotspot in the Earth's underlying mantle. The Hawaii island volcanoes are merely the most recent evidence of this process that, over 70 million years, has created the 6,000 km (3,700 mi)-long Hawaiian–Emperor seamount chain. The prevailing, though not completely settled, view is that the hotspot has been largely stationary within the planet's mantle for much, if not all of the Cenozoic Era. However, while the Hawaiian plume is well-understood and extensively studied, the nature of hotspots themselves remains fairly enigmatic.

Mauna Loa is one of five subaerial volcanoes that make up the island of Hawaiʻi, created by the Hawaii hotspot. The oldest volcano on the island, Kohala, is more than a million years old, and Kīlauea, the youngest, is believed to be between 300,000 and 600,000 years of age; Lōʻihi Seamount on the island's flank is even younger, but has yet to breach the surface. At 1 million to 700,000 years of age, Mauna Loa is the second youngest of the five volcanoes on the lsland, making it the third youngest volcano in the Hawaiian – Emperor seamount chain, a chain of shield volcanoes and seamounts extending from Hawaii to the Kuril–Kamchatka Trench in Russia.

Following the pattern of Hawaiian volcanics, Mauna Loa would have started out as young submarine volcano, gradually building itself up through subsurface eruptions of alkali basalt before emerging from the sea with a series of surtseyan eruptions about 400,000 years ago. Since then the volcano has remained active, generating a continual stream of effusive and explosive eruptions, including 33 historical ones since the first well-documented eruption in 1843. Although Mauna Loa's activity has been overshadowed in recent years by that of its neighbor Kīlauea, it remains active.

Structure

Covering an area of 5,271 km (3,275 mi), Mauna Loa, 60 km (37 mi) wide at its furthest point, is the largest volcano in the world. Consisting of approximately 65,000 to 80,000 km (15,600 to 19,200 cu mi) of solid rock, it makes up more than half of the surface area of the island of Hawaiʻi, with a bulk so massive that it causes the causes the oceanic crust underneath it to sag about 8 km (5 mi). When combined with the volcano's extensive submarine flanks (5 km (3 mi) to the sea floor) and 4,170 m (13,680 ft) subaerial height, Mauna Loa rises an impressive 17 km (11 mi) from base to peak; in comparison, Mount Everest, 8,848 m (29,029 ft) high, is slightly more than half of its true height and a fraction of its volume.

Mauna Loa is a typical shield volcano in form, taking the shape of a long, broad dome extending down to the ocean floor whose slopes are about 12° at their steepest, a consequence of its extremely fluid lava. Mauna Loa's summit hosts three overlapping pit craters arranged northeast-southwest, the first and last roughly 1 km (0.6 mi) in diameter and the second an oblong 4.2 km × 2.5 km (2.6 mi × 1.6 mi) feature; together these three craters make up the 6.2 by 2.5 km (3.9 by 1.6 mi) summit caldera Mokuʻāweoweo, so named for the Hawaiian ʻāweoweo fish (Priacanthus meeki), purportedly due to the resemblance of its eruptive fires to the coloration of the fish. Mokuʻāweoweo's caldera floor lies between 170 and 50 m (558 and 164 ft) beneath its rim and it is only the latest of several calderas that have formed and reformed over the volcano's life. It was created between 1,000 and 1,500 years ago by a large eruption from Mauna Loa's northeast rift zone, which emptied out a shallow magma chamber beneath the summit and collapsed it into its present form. Additionally, two smaller pit craters lie southwest of the caldera, named Lua Hou (New Pit) and Lua Hohonu (Deep Pit); these were last active around 3,000 years ago.

Mauna Loa's summit is also the focal point for its two prominent rift zones, marked on the surface by well-preserved, relatively recent lava flows (easily seen in satellite imagery) and linearly arranged fracture lines intersected by cinder and splatter cones. These rift zones are deeply set structures, driven by dike intrusions along a decollement fault that is believed to reach down all the way to the volcano's base, 12 to 14 km (7 to 9 mi) deep. The first is a 60 km (37 mi) rift trending southwest from the caldera to the sea and a further 40 km (25 mi) underwater, with a prominent 40° directional change along its length; this rift zone is historically active across most of its length. The second, northeastern rift zone extends towards Hilo and is historically active across only the first 20 km (12 mi) of its length, with a nearly straight and, in its latter sections, poorly defined trend. The northeastern rift zone takes the form of a succession of cinder cones, the most prominent of which the 60 m (197 ft) high Puu Ulaula, or Red Hill. There is also a less definite northward rift zone that extends towards the Humuula Saddle marking the intersection of Mauna Loa and Mauna Kea.

Eruptions are typically Hawaiian in character and rarely violent, starting with the emergence of lava fountains over a several kilometer long rift colloquially known as the "curtain of fire" (often, but not always, propagating from Mauna Loa's summit) and eventually concentrating at a single vent, its long-term eruptive center. The shield-stage lavas that built the enormous main mass of the mountain are tholeiitic basalts, like those of Mauna Kea, created through the mixing of primary magma and subducted oceanic crust. Most eruptions are centered at either the summit or either of its two major rift zones; within the last two hundred years, 38 percent of eruptions occurred at the summit, 31 percent at the northeast rift zone, 25 percent at the southwest rift zone, and the remaining 6 percent from northwest vents. 40 percent of the volcano's surface consists of lavas less than a thousand years old, and 98 percent of lavas less than 10,000 years old.

Simplified geophysical models of Mauna Loa's magma chamber have been constructed, using interferometric synthetic aperture radar measures of ground deformation due to the slow buildup of lava under the volcano's surface. These models predict a 1.1 km (1 mi) wide magma chamber located at a depth of about 4.7 km (3 mi), 0.5 km (0 mi) below sea level, near the southeastern margin of Mokuʻāweoweo. This shallow magma chamber is significantly higher-placed than Mauna Loa's rift zones, suggesting magma intrusion into the deeper and occasional dike injections into the shallower parts of the rift zone drive rift activity; a similar mechanism has been proposed for neighboring Kīlauea. Earlier models based on Mauna Loa's two most recent eruptions made a similar prediction, placing the chamber at 3 km (1.9 mi) deep in roughly the same geographic position.

Mauna Loa has complex interactions with its neighbors, Hualālai to the west, Mauna Kea to the north, and particularly Kīlauea to the east. Lavas from Mauna Kea intersect with Mauna Loa's basal flows as a consequence of Kea's older age, and Mauna Kea's original rift zones were buried beneath post-shield volcanism from Mauna Loa; additionally, Mauna Kea shares Mauna Loa's gravity well, depressing the ocean crust beneath it by 6 km (4 mi). There are also a series of normal faults on Mauna Loa's northern and western slopes, between its two major rift zones, that are believed to be the result of combined circumferential tension from the two rift zones and from added pressure do to the westward growth of neighboring Kīlauea.

Because Kīlauea lacks a topographical prominence and appears as a bulge on the southeastern flank of Mauna Loa, it was historically interpreted by both native Hawaiians and early geologists to be an active satellite of Mauna Loa. However, analysis of the chemical composition of lavas from the two volcanoes show that they have separate magma chambers, and are thus distinct. Nonetheless, their proximity has led to a historical trend in which high activity at one volcano roughly coincides with low activity at the other. When Kīlauea lay dormant between 1934 and 1952, Mauna Loa became active, and when the latter remained quiet from 1952 to 1974, the reverse was true. This is not always the case; the 1984 eruption of Mauna Loa started during an eruption at Kīlauea, but had no discernible effect on the Kīlauea eruption, and the ongoing inflation of Mauna Loa's summit, indicative of a future eruption, began the same day as new lava flows at Kīlauea's Puʻu Ōʻō crater. Geologists have suggested that "pulses" of magma entering Mauna Loa's deeper magma system may have increased pressure inside Kīlauea and triggered the concurrent eruptions.

Mauna Loa is slumping eastward along its southwestern rift zone, leveraging its mass into Kīlauea and driving the latter eastward at a rate of about 10 cm (4 in) per year; the interaction between the two volcanoes in this manner has generated a number of large earthquakes in the past, and has resulted in a significant area of debris off of Kīlauea's seaward flank known as the Hilina Slump. A system of older faults exists on the southeastern side of Mauna Loa that likely formed before Kilauea became large enough to impede Mauna Loa's slump, the lowest and northernmost of which, the Kaoiki fault, remains an active earthquake center today. The west side of Mauna Loa, meanwhile, is unimpeded in movement, and indeed is believed to have underwent a massive slump collapse between 100,000 and 200,000 years ago, the residue from which, consisting of a scattering of debris up to several kilometers wide and up to 50 km (31 mi) distant, is still visible today. The damage was so extensive that the headwall of the damage likely intersected its southwestern rift zone. There is very little movement there today, a consequence of the volcano's geometry.

Mauna Loa is tall enough to have experienced glaciation during the last ice age, 25,000 to 15,000 years ago. Unlike Mauna Kea, on which extensive evidence of glaciation remains even today, Mauna Loa was and has remained active at the time, having grown an additional 150 to 300 m (492 to 984 ft) in height since then and covering any glacial deposits beneath new flows; strata of that age doesn't occur until at least 2,000 m (6,562 ft) down from the volcano's summit, too low for glacial growth. Mauna Loa also lacks its neighbor's summit permafrost region, although sporadic ice persists in places. It is speculated that extensive phreatomagmatic activity occurred during this time, contributing extensively to ash deposits on the summit.

Eruptive history

Prehistoric eruptions

Mauna Loa has been subjected to extensive charcoal-based radiocarbon dating that have allowed scientists to reconstruct perhaps the most extensive prehistorical eruptive history of any volcano on Earth, with almost two hundred reliably dated extant flows. To have reached its enormous size within its relatively short (geologically speaking) 600,000 to 1,000,000 years of life, Mauna Loa would logically have had to have grown extremely rapidly through its developmental history, and indeed, geological evidence points to a slowdown in the volcano's activity through the present circa 100,000 years ago.

Studies have shown that a cycle occurs in which volcanic activity at the summit is dominant for several hundred years, after which activity shifts to the rift zones for several more centuries, and then back to the summit again. Two cycles have been clearly identified, each lasting 1,500–2,000 years. This cyclical behavior is unique to Mauna Loa among the Hawaiian volcanoes.

Records show that between about 7,000 and 6,000 years ago Mauna Loa was largely inactive. The cause of this cessation in activity is not known, and no known similar hiatus has been found at other Hawaiian volcanoes except for those currently in the post-shield stage. Between 11,000 and 8,000 years ago, activity was more intense than it is today. However, Mauna Loa's overall rate of growth has probably begun to slow over the last 100,000 years, and the volcano may in fact be nearing the end of its tholeiitic basalt shield-building phase.

Origins

Mauna Loa began erupting between 700,000 and 1,000,000 years ago and has grown steadily since then. Like all of the Hawaiian islands, Mauna Loa has its origins in the Hawaii hotspot—a plume of magma rising from deep in the Earth's mantle. The hotspot remains in a fixed position, while the Pacific Plate drifts over it at a rate of about 4 inches (10 cm) per year. The upwelling of the hot magma creates volcanoes, and each individual volcano erupts for a few million years before the movement of the plate carries it away from the rising magma.

The hotspot has existed for at least 80 million years, and the Emperor Seamounts chain of old volcanoes stretches almost 3,600 miles (5,800 km) away from the hotspot. Currently, the hotspot feeds activity at five volcanoes: Mauna Loa, Kīlauea, and Hualālai on the Big Island, Haleakalā on Maui, and Loʻihi, a submarine volcano south of the Big Island and the youngest Hawaiian volcano. Mauna Loa is the largest of these, although Kīlauea is currently the site of the most intense volcanic activity.

Climate

Trade winds blow from east to west across the Hawaiian islands, and the presence of Mauna Loa strongly affects the local climate. At low elevations, the eastern (windward) side of the volcano receives heavy rain, and the city of Hilo is the wettest in the United States. The rainfall supports extensive forestation. The western (leeward) side has a much drier climate. At higher elevations, the amount of precipitation decreases, and skies are very often clear. Very low temperatures mean that precipitation often occurs in the form of snow, and the summit of Mauna Loa is described as a periglacial region, where freezing and thawing play a significant role in shaping the landscape.

Mauna Loa has a tropical climate with warm temperatures at lower elevations and cool to cold temperatures higher up all year round. Below is the table for the slope observatory, which is at 10,000 feet (3,000 m) in the alpine zone. The highest recorded temperature was 85 °F (29 °C) and the lowest was 18 °F (−8 °C) on February 18, 2003 and February 20, 1962, respectively.

Ascents

Prehistoric

The ʻAinapō Trail was established in prehistoric times, rising from the village of Kapāpala over 11,200 feet (3,400 m) in about 35 miles (56 km). Although the more active and accessible Kīlauea caldera was the usual site to honor the fire goddess Pele, offerings and prayers were also made on Mokuʻāweoweo during its eruptions. Journeys up the trail extended over many days and required many porters. Several established camps along the way supplied water and food.

John Ledyard

John Ledyard led a team to attempt an ascent on the third voyage of Captain James Cook in January 1779. They struggled to go directly up from Kealakekua Bay, but turned back after an estimated 39 kilometres (24 mi), thinking they had about 18 kilometres (11 mi) more to go. The summit was actually only a total of 32 kilometres (20 mi) from the coast.

Archibald Menzies

Archibald Menzies led a party from the Vancouver Expedition in the first successful ascent to Mokuʻāweoweo with a written record. He also first tried a direct route from the west and turned back in February 1793. After arriving again the next year, he climbed to the summit of Hualālai, on the northwest part of the island. He then tried to cross the interior plateau to Mauna Loa, but had to turn back. He consulted King Kamehameha I and was astonished to learn he could take canoes to the south and follow the route established by Ancient Hawaiians known as the ʻAinapō Trail.

On his third attempt on February 16, 1794, Menzies reached the summit and used a barometer to estimate the height as 13,634 feet (4,156 m) compared to its currently known height of 13,679 feet (4,169 m). He was surprised to find heavy snow and morning temperatures of 26 °F (−3 °C). He again underestimated the length of the climb and exhausted food rations, arriving with only three coconuts left for the summit party. The sheer mass of Mauna Loa is deceptive. Slopes are generally not very steep (always less than 12°) which makes it very hard to judge progress on the trail.

Others

On January 29, 1834, 40 years later, another European, David Douglas, reached the summit, also using the ʻAinapō Trail. It is sometimes reported that missionary Joseph Goodrich reached the summit around this time, but he never claimed this himself. He climbed Mauna Kea, and described the sight of Mokuʻāweoweo from Mauna Kea through a telescope. Isidor Löwenstern successfully climbed Mauna Loa in February 1839, only the third successful climb in 60 years.

Wilkes expedition

Wilkes Campsite
U.S. National Register of Historic Places
Sketch by ship's artist Alfred Thomas Agate
Nearest city	Hilo, Hawaii
Area	4 acres (16,000 m)
Built	1840
Architect	Charles Wilkes
Architectural style	Stone shelter
NRHP reference No.	74000295
Added to NRHP	July 24, 1974

The United States Exploring Expedition led by Lieutenant Charles Wilkes was tasked with a vast survey of the Pacific Ocean starting in 1838. In September 1840 they arrived in Honolulu, where repairs to the ships took longer than expected. He decided to spend the winter in Hawaii and take the opportunity to explore its volcanoes while waiting for better weather to continue the expedition. King Kamehameha III assigned American medical missionary Dr. Gerrit P. Judd to the expedition as translator.

Wilkes sailed to Hilo on the island of Hawaiʻi and decided to climb Mauna Loa first, since it looked easier than Mauna Kea. On December 14 he hired about 200 porters, but after he left he realized only about half the equipment had been taken, so had to hire more Hawaiians at higher pay. When they reached Kīlauea after two days, their guide Puhano headed off to the established ʻAinapō Trail. Wilkes did not want to head back downhill so he blazed his own way through dense forest directed by a compass. The Hawaiians were offended by the waste of sacred trees, which did not help morale. At about 6,000 feet (1,800 m) elevation they established a camp called "Sunday Station" at the edge of the forest.

Two guides joined them at Sunday Station: Keaweehu, "the bird-catcher" and another whose Hawaiian name is not recorded, called "ragsdale". Although Wilkes thought he was almost to the summit, the guides knew they were less than half way up. Since there was no water at Sunday Station, porters had to be sent back ten miles (16 km) to a lava tube on ʻAinapō Trail which had a known supply. After an entire day replenishing stocks, they continued up to a second camp they called "Recruiting Station" at about 9,000 feet (2,700 m) elevation. After another full day's hike they established "Flag Station" on December 22, and by this time were on the ʻAinapō Trail. Most of the porters were sent back down to get another load.

At the Flag Station Wilkes and his eight remaining men built a circular wall of lava rocks and covered the shelter with a canvas tent. A snowstorm was in progress and several suffered from altitude sickness. That night (December 23), the snow on the canvas roof caused it to collapse. At daylight some of the group went down the trail to retrieve firewood and the gear abandoned on the trail the day before. After another day's climb, nine men reached the rim of Mokuʻāweoweo. They could not find a way down its steep sides so chose a smooth place on the rim for the camp site, at coordinates 19°27′59″N 155°34′54″W / 19.46639°N 155.58167°W / 19.46639; -155.58167. Their tent was pitched within 60 feet (18 m) of the crater's edge, secured by lava blocks.

The next morning they were unable to start a fire using friction due to the thin air at that altitude, and sent for matches. By this time, the naval officers and Hawaiians could not agree on terms to continue hiring porters, so sailors and marines were ordered from the ships. Dr. Judd traveled between the summit and the Recruiting Station to tend the many who suffered from altitude sickness or had worn out their shoes on the rough rock. Christmas Day was spent building rock walls around the camp to give some protection from the high winds and blowing snow. It took another week to bring all the equipment to the summit, including a pendulum designed for measuring slight variations in gravity.

On December 31, 1840 the pre-fabricated pendulum house was assembled. Axes and chisels cut away the rock surface for the pendulum's base. It took another three days to adjust the clock to the point where the experiments could begin. However, the high winds made so much noise that the ticks could often not be heard, and varied the temperature to make measurements inaccurate. Grass had to be painstakingly brought from the lowest elevations for insulation to get accurate measurements.

On Monday, January 11, Wilkes hiked around the summit crater. Using an optical method, he estimated Mauna Kea was only 193 feet (59 m) higher (modern measurements are 104 feet (32 m) feet). On January 13, 1841, he had "Pendulum Peak, January 1841 U.S. Ex, Ex." cut into a rock at the site. The tents were dismantled and Hawaiians carried the gear down over the next three days, while Wilkes enjoyed a lomilomi Hawaiian massage. He continued his measurements at lower elevations and left the island on March 5. For all the effort he did not obtain any significant results, attributing gravity discrepancies to "the tides".

The Wilkes expedition's camp site's ruins are the only known physical evidence in the Pacific of the U. S. Exploring Expedition. The camp site was listed on the National Register of Historic Places on July 24, 1974 as site 74000295, and is state historic site 10-52-5507.

Today

A summit shelter was built with some of the stones from Wilkes' camp site and mortar in 1934. In 1916 Mokuʻāweoweo was included in Hawaii Volcanoes National Park, and a new trail was built directly from park headquarters at Kīlauea, an even more direct route than the one taken by Wilkes. This trail, arriving at the summit from the east via Red Hill, became the preferred route due to its easier access and gentler slope. After falling into disuse, the historic ʻAinapō Trail was reopened in the 1990s. A third modern route to the summit is from the Saddle Road, up to the Mauna Loa Observatory which is located at the elevation of 11,135 feet (3,394 m) a few miles north of Mokuʻāweoweo, and the North Pit trail.

Historic eruptions

Although Ancient Hawaiians had witnessed eruptions for many centuries, written records exist only for eruptions that have occurred since the early 19th century. The first historical eruption occurred in 1832, and since then 32 eruptions have been documented.

The typical pattern is for an eruption to start at Mokuʻāweoweo, then move to a focal vent lower on one of the rift zones. Often, a major rift eruption is preceded by a smaller event that is limited to Mokuʻāweoweo, a year or more before the larger one. The latter occurred in 1880, 1940, and 1949, before the massive flank eruptions of 1881, 1942, and 1950. In total, these eruptions have covered over 310 square miles (800 km) of the volcano's flanks with lava flows. Typically, eruptions have been brief but intense, with 0.06 to 0.12 cubic miles (0.25–0.5 km³) of lava erupted over a few weeks.

The most prominent historic eruptions of Mauna Loa, with extensive lava flows in forest and agricultural areas, were in 1855, 1881, 1935, 1942, and 1950 on the northeast rift zone; 1887, 1907, 1916, 1919, 1926, and 1950 on the southwest rift zone; and the 1859 radial vent eruption.

An eruption in 1935 that headed toward the city of Hilo led to an unusual employment of air power. Five bombers of the 23d and 72d Bombardment Squadrons of the United States Air Force dropped bombs in the path of the lava in order to divert it away from Hilo. The eruption stopped six days later.

The 1950 eruption produced lava flows along a 20 kilometers (12 mi) fissure from Lua Hou to the southwest. The first flow extended 24 kilometers (15 mi) from the vent at 2,800 meters (9,200 ft) elevation to the ocean in only three hours during the night, and a second flow before dawn cut off the escape route for people in the village of Hoʻokena. The eruption eventually focused on a flow further to the south, which also reached the ocean.

On March 25, 1984 an eruption started: a small summit eruption was followed by a larger flank lava flow that threatened Hilo. Fissures opened to the northwest and southeast, from the summit down to 9,500 feet (2,900 m) above sea level. Flows from this eruption headed rapidly towards Hilo again, but stopped about 2.5 miles (4.0 km) from the outskirts when the eruption ended after three weeks.

As of 2009, Mauna Loa has been inactive for over 25 years, its longest quiet period in recorded history.

Current activity

In 2002 seismic activity, which had been low, increased, and inflation suddenly started, and the caldera walls started to move apart at 2 inches (5 cm) per year. This is thought to indicate that magma is filling a reservoir about 3.1 miles (5.0 km) beneath the summit. The inflation has been intermittent, sometimes slowing, and sometimes stopping for several weeks. Thus far, though, it has always restarted, and this is likely to indicate an increased probability of an eruption in the next few years.

In July 2004 a swarm of deep earthquakes began, and continued until the end of the year. Earthquakes were detected at a rate of one per day for the first three weeks, increasing steadily over subsequent months to 15 or so per day by the end of the year. The swarm ended in December 2004, and earthquake levels have been only moderately elevated since then.

Hazards

Volcanic eruptions in Hawaiʻi rarely cause casualties: the only fatality due to volcanic activity there in the last century occurred at Kīlauea in 1924, when an unusually explosive eruption hurled rocks at onlookers, killing one. However, property damage is common. Mauna Loa is a Decade Volcano, which means the IAVCEI has identified it as worthy of particular research in light of its frequent eruptions and proximity to populated areas. Many towns and villages near the volcano are built on lava which has erupted in the last two hundred years, and there is a very strong likelihood that future eruptions will cause damage to populated areas.

Areas of the volcano have been classified into different Lava Flow Hazard Zones. There are two classifications. One classification is based upon historical flows and uses a 1-9 numbering system. The second classification was created to account for present flow activity and uses the numbers 11, 12 and 13.

Lava flows

The main volcanic hazard at Mauna Loa is lava flows. Most flows advance at about walking pace and present little danger to human life, but eruptions at Mauna Loa can be more intense than those at Kīlauea; for example, the 1984 eruption emitted as much lava in three weeks as Kīlauea's current eruption produces in three years. Such high emission rates can generate comparatively fast-moving flows.

Two eruptions of Mauna Loa have destroyed villages. In 1926, the village of Hoʻōpūloa Makai was overrun by lava flows. In 1950, the most voluminous eruption ever seen at Mauna Loa sent lava flows racing towards the sea. The village of Hoʻokena Mauka was destroyed on June 2, 1950 by the advancing flows. Hilo is partly built on lava from the 1880-81 eruption and is at risk from further lava flows. The brief but intense 1984 eruption saw lava flow towards Hilo, but it had not reached any buildings when the eruption stopped.

Flank collapse

A rarer but potentially greater hazard at Mauna Loa is the possibility of a sudden massive collapse of the volcano's flanks. Deep faults allow large portions of the sides of Hawaiian mountains to slide gradually downwards, the best known example being the Hilina Slump. (There is also the more ancient example of the Ninole Hills.) Occasionally, a large earthquake can trigger a collapse of the flank, creating a massive landslide which may trigger a tsunami. Kealakekua Bay, on the western slope of Mauna Loa, was created by such an event. Undersea surveying has revealed numerous landslides along the Hawaiian chain and two giant tsunamis are known to have occurred: 200,000 years ago, Molokaʻi experienced a 246-foot (75 m) tsunami, and 100,000 years ago a megatsunami 1,066 feet (325 m) high struck Lānaʻi.

A recent example of the risks associated with slumps occurred in 1975, when the Hilina Slump suddenly moved forward by several yards. A magnitude 7.2 earthquake resulted which triggered a small tsunami with a wave height of a few yards, killing two campers at Halape.

Monitoring

Mauna Loa is an intensively monitored volcano. The Hawaiian Volcano Observatory (HVO) was established in 1912 to observe the Hawaiian volcanoes, and the HVO has developed many techniques to help predict when eruptions at Mauna Loa and other volcanoes are imminent.

One of the most important tools is seismometry. More than 60 seismometers around the Big Island enable scientists to measure the intensities and locations of hundreds of small earthquakes every week. Earthquakes can begin to increase years before an eruption actually starts: The 1975 and 1984 eruptions were both preceded by one to two years of increased seismic activity at depths of less than 8 miles (13 km).

Another type of seismic activity occurs in the hours preceding an eruption. So-called harmonic tremor is a continuous "rumble" which contrasts with the normal seismic activity of sudden shocks and is believed to be caused by the rapid movement of magma underground. Volcanic tremor normally indicates an imminent eruption, although it may also be caused by shallow intrusions of magma which do not reach the surface.

Another important indicator of what is happening underground is the shape of the mountain. Tiltmeters measure very small changes in the profile of the mountain, and sensitive equipment measures distances between points on the mountain. As magma fills the shallow reservoirs below the summit and rift zones, the mountain inflates. A survey line across the caldera measured a 3-inch (76 mm) increase in its width over the year preceding the 1975 eruption and a similar increase before the 1984 eruption.

Observatories

The location of Mauna Loa has made it an important location for atmospheric monitoring by the Global Atmosphere Watch and other scientific observations. The Mauna Loa Solar Observatory (MLSO), located at 11,155 feet (3,400 m) on the northern slope of the mountain, has long been prominent in observations of the Sun. The NOAA Mauna Loa Observatory (MLO) is located close by. From its location well above local human-generated influences, the MLO monitors the global atmosphere, including the greenhouse gas carbon dioxide. Measurements are adjusted to account for local outgassing of CO₂ from the volcano.

Since October 2006, the Array for Microwave Background Anisotropy (AMIBA) has been exploring the origin of the universe.

The Hawaiian Volcano Observatory maintains seismic sensors and a web cam on Mokuʻāweoweo.

See also

• Outline of Hawaii
• Index of Hawaii-related articles
• Evolution of Hawaiian volcanoes
• List of Ultras in Oceania
• List of Ultras in the United States
• Mountain peaks of Hawaii
• Mountain peaks of the United States
• Table of the major 4000 meter summits of the United States

References

1. ^ "Mauna Loa, Hawaii". Peakbagger.com. Retrieved 12 December 2012.
2. ^ "Mauna Loa: Earth's Largest Volcano". Hawaiian Volcano Observatory—United States Geological Service. 2 February 2006. Retrieved 9 December 2012.
3. Kaye, G.D. (2002). "Using GIS to estimate the total volume of Mauna Loa Volcano, Hawaii". 98th Annual Meeting. Geological Society of America. {{cite conference}}: Unknown parameter |booktitle= ignored (|book-title= suggested) (help)
4. "Biggest Mountain: Mauna Loa". Extreme Science. Retrieved 2012-01-27.
5. "Mauna Loa: Earth's Largest Volcano". United States Geological Survey. February 2, 2006. Retrieved 2007-07-28.
6. ^ David R. Sherrod, John M. Sinton, Sarah E. Watkins, and Kelly M. Brunt (2007). "Geologic Map of the State of Hawai'i" (PDF). Open-File Report 2007–1089. United States Geological Survey. pp. 50–51. Retrieved 9 December 2012.{{cite web}}: CS1 maint: multiple names: authors list (link)
7. ^ Watson, Jim (May 5, 1999). "The long trail of the Hawaiian hotspot". United States Geological Survey. Retrieved August 26, 2010.
8. "The Emperor and Hawaiian Volcanic Chains: How well do they fit the plume hypothesis?". MantlePlumes.org. March 11, 2006. Retrieved April 1, 2009. {{cite web}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
9. David A. Clague, G. Brent Dalrymple (1987). "The Hawaiian-Emperor Volcanic Chain – Geological Evolution". Volcanism in Hawaii: papers to commemorate the 75th anniversary of the founding of the Hawaii Volcano Observatory (PDF). Professional Paper 1350. Vol. 1. United States Geological Survey. p. 32.
10. ^ "Kīlauea – Perhaps the World's Most Active Volcano". Hawaiian Volcano Observatory—United States Geological Survey. 7 May 2009. Retrieved 27 January 2012.
11. "Kohala—Hawai``i's Oldest Volcano". Hawaiian Volcano Observatory—United States Geological Survey. 20 March 1998. Retrieved 29 January 2012.
12. "Lo`ihi Seamount Hawai`i's Youngest Submarine Volcano". Hawaiian Volcano Observatory—United States Geological Survey. 26 March 2000. Retrieved 30 January 2012.
13. W. J. Kious and R. I. Tilling (1996). "Hotspots": Mantle thermal plumes (1.14 ed.). United States Geological Survey. ISBN 0160482208. Retrieved 9 December 2012.
14. "Evolution of Hawaiian Volcanoes". Hawaiian Volcano Observatory—United States Geological Survey. 26 March 1998. Retrieved 30 January 2012.
15. ^ G. MacDonald and D. Hubbard (24 March 2006). "Mauna Loa, Fiery Colossus of the Pacific". National Park Service. Retrieved 9 December 2012. {{cite web}}: Check date values in: |year= / |date= mismatch (help)
16. Ken Rubin and Rochelle Minicola (20 March 2009). "Mauna Loa Volcano". Hawaiian Volcano Observatory—United States Geological Survey. Retrieved 12 December 2012.
17. Navin Singh Khadka (28 February 2012). "Nepal in new bid to finally settle Mount Everest height". BBC News. Retrieved 10 December 2012.
18. ^ "When did Moku`aweoweo (the summit caldera of Mauna Loa) form?". Hawaiian Volcano Observatory—United States Geological Survey. 28 March 2001. Retrieved 11 December 2012.
19. "Place Names of Hawaii - Moku-ʻāweoweo". Ulukau - Hawaiian Electronic Library. Retrieved 11 December 2012.
20. John Watson (5 January 1997). "Eruptions of Hawaiian Volcanoes [USGS]". United States Geological Survey. Retrieved 16 December 2012.
21. ^ Peter W. Lipman (1980). "The Southwestern Rift Zone of Mauna Kea: Implications for Structural Evolution of Hawaiian Volcanoes". American Journal of Science. 280-A. American Journal of Science: 752–776. {{cite journal}}: |access-date= requires |url= (help)
22. ^ F. Amelung, S. H. Yun, T. R. Walter, P. Segall, S. W. Kim (18 May 2007). "Stress Control of Deep Rift Intrusion at Mauna Loa Volcano, Hawaii". Science. 316 (5827). American Association for the Advancement of Science: 1026–1030. doi:10.1126/science.1140035. Retrieved 16 December 2012.{{cite journal}}: CS1 maint: multiple names: authors list (link)
23. Claude Herzberg (30 November 2006). "Petrology and thermal structure of the Hawaiian plume from Mauna Kea volcano". Nature. 444 (7119). Nature Publishing Group: 605–9. Bibcode:2006Natur.444..605H. doi:10.1038/nature05254. PMID 17136091. Retrieved 10 December 2012.
24. ^ Ken Rubin and Rochelle Minicola (7 March 2007). "Mauna Loa Eruption History". Hawaii Center for Volcanology. Retrieved 12 December 2012.
25. John Watson (18 July 1997). "Lava Flow Hazard Zone Maps: Mauna Loa". United States Geological Survey. Retrieved 12 December 2012.
26. ^ "Eruption History". Hawaiian Volcano Observatory—United States Geological Survey. 2 February 2006. Retrieved 16 December 2012.
27. "What's up with Mauna Loa?". Hawaiian Volcano Observatory - United States Geological Survey. 23 October 2001. Retrieved 16 December 2012.
28. ^ E. W. Wolfe, W. S. Wise, G. B. Dalrymple (1997). The geology and petrology of Mauna Kea volcano, Hawaii : a study of postshield volcanism. Professional Paper 1557. United States Geological Survey. Retrieved 12 December 2012.{{cite book}}: CS1 maint: multiple names: authors list (link)
29. E. C. Cannon and R. R. Bürgmann (26 October 2009). "Complete Report for Mauna Kea Volcano (Class B) No. 2601". United States Geological Survey. Retrieved 12 December 2012.
30. "Rift Zones". Oregon State University. Retrieved 13 December 2012.
31. "Inflation of Mauna Loa Volcano slows". Volcano Watch. Hawaiian Volcano Observatory—United States Geological Survey. 28 January 2003. Retrieved 30 January 2012.
32. Ken Hon. "Giant Landslides: Kilauea and Mauna Loa: GEOL 205: Lecture Notes". University of Hawaii at Hilo. Retrieved 16 December 2012.
33. "Glaciers on Mauna Kea? You crazy? In the middle of the Pacific? YES!". Hawaiian Volcano Observatory - United States Geological Survey. 22 October 2007. Retrieved 16 December 2012.
34. "Eruption History: A Cyclic Eruption Model is Proposed". HVO. 16 March 1998. Retrieved 25 December 2012.
35. Lockwood J.P. (1995), "Mauna Loa eruptive history - the preliminary radiocarbon record", in Rhodes, J.M. and Lockwood, J.P. (eds.), Mauna Loa revealed: structure, composition, history, and hazards, Washington D.C., American Geophysical Union Monograph 92, p. 81–94.
36. "Eruption History of Mauna Loa Volcano". United States Geological Survey, Hawaiian Volcano Observatory. Retrieved 2007-07-28.
37. "Eruption History: A Cyclic Eruption Model is Proposed". United States Geological Survey, Hawaiian Volcano Observatory. March 16, 1998. Retrieved 2007-07-28.
38. ^ Decker R, Decker B (1997). Volcanoes, W.H. Freeman & Co, Ltd, ISBN 0-7167-3174-6
39. Rubin, Ken (2004). "Mauna Loa Flora and Climate". Hawaii Center for Volcanology. Retrieved 2007-07-28. {{cite web}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
40. "Period of Record General Climate Summary - Temperature". MAUNA LOA SLOPE OBS, HAWAII. NOAA. Retrieved 2012-06-05.
41. "Period of Record Monthly Climate Summary". MAUNA LOA SLOPE OBS, HAWAII. NOAA. Retrieved 2012-06-05.
42. ^ Russell A. Apple (July 18, 1973). Template:PDFlink. National Register of Historic Places, National Park Service.
43. ^ Roberta A. Sprague (1991). "Measuring the Mountain: the United States Exploring Expedition on Mauna Loa, 1840-1841". Hawaiian Journal of History. 25. Hawaiian Historical Society, Honolulu. hdl:10524/359.
44. ^ Walther M. Barnard (1991). "Earliest Ascents of Mauna Loa Volcano, Hawai'i". Hawaiian Journal of History. 25. Hawaiian Historical Society, Honolulu. hdl:10524/599.
45. ^ Archibald Menzies (1920). William Frederick Wilson (ed.). Hawaii Nei 128 Years Ago: Journal of Archibald Menzies, kept during his three visits to the Sandwich or Hawaiian Islands in the years 1792-1794. s.n. p. 197. Retrieved 2009-07-04.
46. ^ Gordon A. Macdonald, Douglass H. Hubbard (Original 1951, revised 1974). Volcanoes of the National Parks of Hawaii. National Park Service web site. {{cite book}}: Check date values in: |year= (help)CS1 maint: year (link)
47. ^ "National Register Information System". National Register of Historic Places. National Park Service. March 13, 2009.
48. Charles Wilkes (1849). Narrative of the United States Exploring Expedition. Vol. Volume IV. G. P. Putnam. p. Pages 111–162. {{cite book}}: |volume= has extra text (help)
49. ^ Russell A. Apple (1973). "Wilkes Campsite Nomination form" (PDF). National Register of Historic Places. National Park Service.
50. Historic Places in Hawaii County on official state web site
51. "NOAA Mauna Loa Observatory". National Oceanic and Atmospheric Administration web site. Retrieved 2009-07-04.
52. ^ Eruption History of Mauna Loa from the USGS
53. USAF history page (PDF). 27 Dec 1935 Five Keystone LB-5 bombers of the 23d and 72d Bombardment Squadrons at Luke Field dropped twenty 600-pound bombs in the path of a lava flow from the Mauna Loa volcano on the Big Island.
54. 23rd Bomb Squadron history from Minot Air Force Base website.
55. "TERRITORIES: Mauna Loa Erupts". Time. April 22, 1940.
56. "50th Anniversary of Mauna Loa's Most Spectacular Eruption". USGS Hawaii Volcano Observatory. 2000. Retrieved 2009-07-04.
57. ^ "The 1950 eruption of Mauna Loa: a nightmare that could reoccur". USGS, Hawaiian Volcano Observatory. May 10, 2001. Retrieved 2007-07-28.
58. "1984 Eruption of Mauna Loa". USGS Hawaiian Volcano Observatory. 1987. Retrieved 2009-07-04.
59. "Mauna Loa: Summary of monitoring data (1970 – May 2005)". United States Geological Survey, Hawaiian Volcano Observatory. June 22, 2005. Retrieved 2007-07-28.
60. Heliker CC (July 18, 1997). "Volcanic and seismic hazards on the island of Hawaii". US Geological Survey General Interest Publication. Retrieved 2007-07-28.
61. International Association of Volcanology and Chemistry of the Earth's Interior (1998). "Decade Volcanoes". Cascades Volcano Observatory. Vancouver, Washington, USA: USGS.
62. Finch R.H., Macdonald G.A. (1950), The June 1950 eruption of Mauna Loa, Part I, Volcano Letter, v.508, p12
63. "Lava flow hazards on Mauna Loa volcano". USGS, Hawaiian Volcano Observatory. February 2, 2006. Retrieved 2007-07-28.
64. Cannon EC, Bürgmann R, Owen SE (2001), Shallow Normal Faulting and Block Rotation Associated with the 1975 Kalapana Earthquake, Kilauea, Bulletin of the Seismological Society of America
65. Rhodes, J.M. and Lockwood, J. P. (editors), (1995) Mauna Loa Revealed: Structure, Composition, History, and Hazards, Washington D.C., American Geophysical Union Monograph 92, page 95
66. "Live panorama of Mokuaweoweo". United States Geological Survey, Hawaii Volcanoes Observatory web site. Retrieved 2009-07-04.

External links

• United States Geological Survey information page
• VolcanoWorld information
• Hawaii Center for Volcanology pages
• Global Volcanism Program entry
• Mauna Loa Observatory (MLO) – NOAA
• Mauna Loa Solar Observatory (MLSO)
• 1934 USGS color video (silent) of Mauna Loa erupting

v t e Hawaiian volcanism topics (list)
Windward Isles	South Arch volcanic field Kamaʻehuakanaloa Māhukona Hawaiʻi Kīlauea (Kīlauea Iki, Pauahi Crater, Puʻu ʻŌʻō, Mauna Ulu) Mauna Loa Hualālai Mauna Kea Kohala Kahoʻolawe Kauaʻi Kaʻula Lānaʻi Maui Haleakalā West Maui Molokaʻi Penguin Bank West Molokai Volcano East Molokai Volcano Niʻihau Oʻahu Honolulu Kaʻena Koʻolau North Arch volcanic field Waiʻanae
Leeward Isles	French Frigate Shoals Gardner Pinnacles Kure Atoll Laysan Lisianski Island Maro Reef Midway Atoll Necker Island Nihoa Pearl and Hermes Atoll
Emperor Seamounts	Abbott Colahan Daikakuji Detroit Hancock Jingū Kammu Kimmei Koko Meiji Nintoku Ojin Suiko Yomei Yuryaku
Notable eruptions and vents	1955 Hawaiian submarine eruption 1975 eruption of Mauna Loa 1984 eruption of Mauna Loa 2018 lower Puna eruption 2022 eruption of Mauna Loa Keanakakoi eruption ʻAilāʻau eruption Halemaʻumaʻu Kīlauea Caldera Kīlauea Iki Mauna Ulu Powers Caldera Puʻu ʻŌʻō
Topics	ʻAʻā (lava) Evolution of Hawaiian volcanoes Haleakalā National Park Hawaiʻi Volcanoes National Park Hawaiian–Emperor seamount chain Hawaiian eruption Hawaiian Volcano Observatory Kīlauea eruptions Lava fountain Limu o Pele Mauna Loa eruptions Pāhoehoe (lava) Pele (deity) Pele's hair Pele's tears Puna Geothermal Venture Volcano House

Template:Link FA Template:Link FA

• Ill-formatted IPAc-en transclusions
• Active volcanoes
• Decade Volcanoes
• Extreme points of Earth
• Mountains of Hawaii
• United States National Park high points
• Shield volcanoes
• Volcanic calderas of Hawaii
• Volcanoes of the Island of Hawaii
• Hotspot volcanoes
• VEI-2 volcanoes
• Hawaiʻi Volcanoes National Park
• National Register of Historic Places in Hawaii
• Pleistocene volcanoes