Mauna Loa ( or ; Hawaiian: ; ) is one of five volcanoes that form the Island of Hawaii in the U.S. state of Hawaiʻi in the Pacific Ocean. The largest subaerial volcano in both mass and volume, Mauna Loa has historically been considered the largest volcano on Earth, dwarfed only by Tamu Massif. It is an active shield volcano with relatively gentle slopes, with a volume estimated at approximately , although its peak is about lower than that of its neighbor, Mauna Kea. Lava eruptions from Mauna Loa are silica-poor and very fluid, and they tend to be non-explosive.
Introduction
Mauna Loa
Mauna Loa | Introduction
It is one of five volcanoes that form the Island of Hawaii in the U.S. state of Hawaiʻi in the Pacific Ocean. It  is one of five volcanoes that form the Island of Hawaii in the U.S. state of Hawaiʻi in the Pacific Ocean. Mauna Loa ( or ; Hawaiian: ; ) is one of five volcanoes that form the Island of Hawaii in the U.S. state of Hawaiʻi in the Pacific Ocean. It is one of five volcanoes that form the Island of Hawaii in the U.S. state of Hawaiʻi in the Pacific Ocean.
when was the last time mauna loa volcano erupted
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March 24 to April 15, 1984.
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what is the main entity?
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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.
Mauna Loa | Prehistoric eruptions
By mid-afternoon, eruptive activity began to decrease at the uppermost vents between . At 4:41 p.m., a new fissure opened up at the elevation. This fissure rapidly migrated both uprift and downrift, so that by 6:30 p.m., a line of lava fountains slightly longer than was active. Eventually the fissure system condensed to four centers of activity with fountains up to 50 m (165 ft) high. Four parallel flows (flows D on map) moved down the northeast flank at speeds as fast as per hour. All vents uprift from these new ones quickly became inactive and the eruptive activity was confined to these vents for the next three weeks.
1984 eruption of Mauna Loa | Eruption
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. 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. Mauna Loa's summit hosts three overlapping pit craters arranged northeast-southwest, the first and last roughly in diameter and the second an oblong feature; together these three craters make up the 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.
Mauna Loa | Structure
The main volcano is of rhyodacitic composition and has generated two major ignimbritic eruptions, one 1.5 million years ago and a second 67,000 years ago. The last eruption was 28,000 years ago, but the volcano is a candidate source for a Holocene eruption and it may become active in the future.
Nevado Tres Cruces | Introduction
The 1984 eruption of Mauna Loa was a Hawaiian eruption in the U.S. state of Hawaii that lasted from March 25 to April 15, 1984. It ended a 9-year period of quiescence at the volcano and continued for 22 days, during which time lava flows and lava fountains issued from the summit caldera and fissures along the northeast and southwest rift zones. Although the lava threatened Hilo, the flow stopped before reaching the outskirts of town.
1984 eruption of Mauna Loa | Introduction
Mokuʻāweoweo's caldera floor lies between 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). 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.
Mauna Loa | Structure
A voluminous a'a flow moved about down the north flank of Mauna Loa and threatened to cut the paved access road and powerlines to the Mauna Loa Observatory. At about 07:15 HST, fountains feeding this a'a flow subsided and it soon stopped about from the observatory road, having traveled . Fountaining continued at greatly diminished levels throughout the day, but ceased by nightfall. Approximately of lava had been erupted and of the Mauna Loa summit area had been covered.
1975 eruption of Mauna Loa | Eruption
Further eruptions occurred in 1879 and then twice in 1880, the latter of which extended into 1881 and came within the present boundaries of the island's largest city, Hilo; however, at the time, the settlement was a shore-side village located further down the volcano's slope, and so was unaffected.
Mauna Loa | Recent history
The 1975 eruption of Mauna Loa was a short-lived Hawaiian eruption that followed 25 years of quiescence at the Hawaiian volcano Mauna Loa. The eruption began just before midnight on July 5 and involved fissures extending across the length of Moku‘āweoweo, Mauna Loa's summit caldera, and into the upper ends of the volcano's northeast and southwest rift zones. After only 6 hours, activity in Moku‘āweoweo and on the southwest rift zone ended, but lava fountaining continued along the northeast rift zone until 7:30 p.m. on July 6, when all activity ceased.
1975 eruption of Mauna Loa | Introduction
Six large vent structures eventually formed in this area around the active vents. By daybreak on March 26, these vents were feeding lava to a fast-moving flow (flow E on map) that had advanced to the northeast and three less active, shorter flows (flows D on map) that were advancing east toward Kulani Prison. The prison was put on alert because the shorter lava flows were as close as to the prison. These flows, however, stopped advancing within 48 hours and never crossed the Powerline Road. The fast-moving flow (flow E on map) advanced as a relatively narrow, channelized ‘a‘ā lava flow.
1984 eruption of Mauna Loa | Eruption
Its rate of advance slowed as it moved downslope, but by March 29 the flow had moved to an elevation of . At this time, the flow front was about from the outskirts of Hilo. Smoke from burning vegetation, loud explosions caused by methane gas along the advancing flow front and the intense glow at night all contributed to a growing concern among Hilo's residents.
1984 eruption of Mauna Loa | Eruption
Since then, the volcano has remained active, with a history of effusive and explosive eruptions, including 33 eruptions 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.
Mauna Loa | Setting
This is a list of volcanic eruptions from Mauna Loa, an active shield volcano in the Hawaiian Islands that last erupted in 1984. These eruptions have taken place from the main caldera and fissures along rift zones. They are generally fluid (VEI-0) Hawaiian eruptions but more violent eruptions have occurred throughout Mauna Loa's eruptive history, with the largest recorded explosive eruptions having taken place in the 19th century.
List of Mauna Loa eruptions | Introduction
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. 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.
Mauna Loa | Prehistoric eruptions
Mauna Loa is the largest subaerial and second largest overall volcano in the world (behind Tamu Massif), covering a land area of and spans a maximum width of . Consisting of approximately of solid rock, it makes up more than half of the surface area of the island of Hawaiʻi. Combining the volcano's extensive submarine flanks ( to the sea floor) and subaerial height, Mauna Loa rises from base to summit, greater than the elevation of Mount Everest from sea level to its summit. In addition, much of the mountain is invisible even underwater: its mass depresses the crust beneath it by another , in the shape of an inverse mountain, meaning the total height of Mauna Loa from the start of its eruptive history is about .
Mauna Loa | Structure
Forming lava fountains similar to those observed in Hawaiian eruptions, the shield volcanoes erupted incandescent lava bombs and were deposited on the southern, western, and eastern flanks of the complex. They have average thicknesses of . Roughly 215,000 years ago, another flank vent erupted dacitic lava that coursed to the west for at least , with volcanic dikes that trend toward the vent still present in the Mazama caldera wall. The complex remained inactive for about 40,000 years before it resumed activity, erupting andesitic lava from another flank vent, building a large shield volcano from 170,000 to 120,000 years ago.
Mount Mazama | Early activity
On the Island of Hawaii, geologists have long recognized deposits formed by glaciers on Mauna Kea during recent ice ages. The latest work indicates that deposits of three glacial episodes since 150,000 to 200,000 years ago are preserved on the volcano. Glacial moraines on the volcano formed about 70,000 years ago and from about 40,000 to 13,000 years ago. If glacial deposits were formed on Mauna Loa, they have long since been buried by younger lava flows.
Last Glacial Maximum | North America
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. In addition to the summit and rift zones, Mauna Loa's northwestern flank has also been the source of three historical eruptions. The 1843 event was followed by eruptions in 1849, 1851, 1852, and 1855, with the 1855 flows being particularly extensive. 1859 marked the largest of the three historical flows that have been centered on Mauna Loa's northwestern flank, producing a long lava flow that reached the ocean on Hawaii island's west coast, north of Kīholo Bay.
Mauna Loa | Recent history
Hawaii Volcanoes National Park covers the summit and the southeastern flank of the volcano, and also incorporates Kīlauea, a separate volcano.
Mauna Loa | Introduction
Data obtained from the Global Volcanism Program website.
List of Mauna Loa eruptions | Historically-observed eruptions
These are followed by two units of lava flows separated by an intervening ash layer known as the Pāhala ash layer: the older Kahuka basalt, sparsely exposed on the lower southwest rift, and the younger and far more widespread Kaʻu basalt, which appear more widely on the volcano. The Pāhala ashes themselves were produced over a long period of time circa 13 to 30 thousand years ago, although heavy vitrification and interactions with post and pre- creation flows has hindered exact dating. Their age roughly corresponding with the glaciation of Mauna Loa during the last ice age, raising the distinct possibility that it is the product of phreatomagmatic interaction between the long-gone glaciers and Mauna Loa's eruptive activities.
Mauna Loa | Prehistoric eruptions
About 130 volcanic vents belong to the field, whose activity began 1.5million years ago and continued into the Holocene. Three major caldera-forming eruptions took place in the volcanic field prior to the last glacial period. Postglacial volcanic activity has included eruptions with simultaneous explosive and effusive components, as well as eruptions with only one component. The most recent eruptions in the volcanic field took place , and ago and generated lava flows; today geothermal phenomena occur at Laguna del Maule. Volcanic rocks in the field include basalt, andesite, dacite and rhyolite; the latter along with rhyodacite makes up most of the Holocene rocks.
Laguna del Maule (volcano) | Introduction
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.
Mauna Loa | Introduction
Historical eruptions at Mauna Loa 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. Activity centered on its summit are usually followed by flank eruptions up to a few months distant, and although Mauna Loa is historically less active than that of its neighbor Kilauea, it tends to produce greater volumes of lava over shorter periods of time. 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.
Mauna Loa | Recent history
It was established in October 2006 by the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) to examine cosmic microwave background radiation.
Mauna Loa | Observatories
Data obtained from the Global Volcanism Program website.
List of Mauna Loa eruptions | Radiocarbon-dated eruptions
Established on Kīlauea in 1912, the Hawaiian Volcano Observatory (HVO), presently a branch of the United States Geological Survey, is the primary organization associated with the monitoring, observance, and study of Hawaiian volcanoes. Thomas A. Jaggar, the observatory's founder, attempted a summit expedition to Mauna Loa to observe its 1914 eruption, but was rebuffed by the arduous trek required (see Ascents). After soliciting help from Lorrin A. Thurston, in 1915 he was able to persuade the US Army to construct a "simple route to the summit" for public and scientific use, a project completed in December of that year; the Observatory has maintained a presence on the volcano ever since.
Mauna Loa | Monitoring
The last eruption formed a lava dome within the collapse scar and the summit area. This eruption occurred about 5,700 years ago. A secondary collapse of the lava dome formed a large block and ash flow that descended the eastern slopes and covers a surface area of about .
Nevado de Longaví | Holocene
At this time the volcano started to produce regular lava flows, accompanied by intermittent explosions of gases. This was the regular activity of the volcano until May 5, 1998.
Arenal Volcano | March 1996
The eruption started as a fissure between two pit craters, Āloi and Alae, where the Mauna Ulu shield would eventually form. Both pāhoehoe and aā lava erupted from the volcano. Early on, fountains of lava burst out as much as 540 meters (1772 ft) high. In early 1973, an earthquake occurred that caused Kīlauea to briefly stop erupting near the original Mauna Ulu site and instead erupt near the craters Pauahi and Hiiaka.
Kīlauea | 1952 to 1982
There is also a less definite northward rift zone that extends towards the Humuula Saddle marking the intersection of Mauna Loa and Mauna Kea.
Mauna Loa | Structure
Lava flows were rapidly advancing to the west and southwest from the southwest rift zone vents. The eruptive fissures extended rapidly northeastward, across North Pit, and into the upper northeast rift zone at 02:25 HST. At 02:45 HST lava from the North Pit vents began cascading into another summit pit crater, Lua Poholo. By 03:15 HST, the lava fountains on the southwest rift zone and within Moku‘āweoweo were waning, and the lava flows moving to the west and southwest had stagnated. Fountains continued to migrate eastward along the northeast rift zone, but by dawn eruptive activity was largely restricted to echelon vents near the northeast rift zone at elevation.
1975 eruption of Mauna Loa | Eruption
Mauna Loa erupted in 1940 and 1942, and Mac was given time to describe those eruptions; he met Thomas A. Jaggar (1871–1953, HVO's first director), then retired in Honolulu. On the morning of 1 April 1946 an Aleutian tsunami struck Hawaii. Macdonald, Francis Shepard of Scripps and Doak Cox, geologist for the Hawaii Sugar Planter's Association, wrote a study on it.
Gordon A. MacDonald | Life
The present main structure dates from 2006.
Morioka Hachimangū | History
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 Puu Ōō crater. In 2002, Kilauea experienced a high-volume effusive episode at the same time that Mauna Loa began inflating. This unexpected communication is evidence of crustal-level interactions between Mauna Loa and Kīlauea, even though these two volcanoes are thought to be fairly independent of each other. 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.
Kīlauea | Structure
At 23:42 HST, a small glow was noted above the southwest end of Moku‘āweoweo. Within one minute the glow extended across the entire summit area and a fume cloud more than high was illuminated with a bright orange-red glow from the unseen lava fountains on the caldera floor. A light airplane with two HVO staff members aboard reached the summit area on July 6 at 01:48 HST; a line of lava fountains high crossed the entire floor of Moku‘āweoweo at this time and extended about down the southwest rift zone. Lava cascades high were pouring into three pit craters on the upper southwest rift zone.
1975 eruption of Mauna Loa | Eruption
A potentially greater hazard at Mauna Loa is a sudden, massive collapse of the volcano's flanks, like the one that struck the volcano's west flank between 100,000 and 200,000 years ago and formed the present-day Kealakekua Bay. Deep fault lines are a common feature on Hawaiian volcanoes, allowing large portions of their flanks to gradually slide downwards and forming structures like the Hilina Slump and the ancient Ninole Hills; large earthquakes could trigger rapid flank collapses along these lines, creating massive landslides and possibly triggering equally large tsunamis. Undersea surveys have revealed numerous landslides along the Hawaiian chain and evidence of two such giant tsunami events: 200,000 years ago, Molokaʻi experienced a tsunami, and 100,000 years ago a megatsunami high struck Lānaʻi.
Mauna Loa | Hazards
A more recent example of the risks associated with slumps occurred in 1975, when the Hilina Slump suddenly lurched forward several meters, triggering a 7.2 earthquake and a tsunami that killed two campers at Halape.
Mauna Loa | Hazards
The last eruption occurred around 1500 BC. The centre of activity was Deriba Caldera, and involved caldera collapse following the eruption of pumice and pyroclastic flows which travelled over from the volcano.
Marrah Mountains | Geography
All the islands have disappeared from wave action and caldera floor movements. In 1959, the island reappeared for a short time and again in 1971. The last structure remained an island until 1975. Activity at present at Kuwae is confined to intermittent fumarole activity, which stain the water yellow. Over the top of the volcano hydrogen sulfide bubbles reach the surface.
Kuwae | Recent activity
Lava flows near the summit have an average thickness of . Secondary volcanic craters produced lava flows and pyroclastic material, which traveled both north and south of the volcano. Cone-building eruptions ceased before the Pleistocene epoch's glacial period, allowing the expanded glacial cover to remove most of the cone, especially on the eastern and northeastern sides. During the ongoing Holocene epoch, there has been volcanic activity between the Three Sisters volcanoes and Three Fingered Jack. Such eruptive episodes have produced tephra and lava flows that cover several hundred square kilometers in the region. These eruptions occurred after the climactic eruption of Mount Mazama, which took place roughly 6,600 years ago.
Three Fingered Jack | Eruptive history
The main shield-building stage of volcanism ended about 470,000 years ago. The summit of the shield volcano subsided below sea level between 435,000 and 365,000 years ago. This makes Māhukona the oldest volcano to build Hawaii island, compared to Kohala to the east and Mauna Kea to the east. The Monterey Bay Aquarium Research Institute investigated the area with a remotely controlled submarine in 2001. It was named for the area known as Māhukona, on the shore to the northeast.
Māhukona | Introduction
At 10:55 p.m. on March 24, small earthquakes began at a rate of 2–3 per minute. By 11:30 p.m., the seismic background increased, marking the onset of tremor. Just before 1:00 a.m. on March 25, the tremor amplitude increased to the point that the astronomical telescopes on Mauna Kea, to the northwest, could not be stabilized due to the constant ground vibration.
1984 eruption of Mauna Loa | Precursors
Kīlauea lacks a topographical prominence, appearing only as a bulge on the southeastern flank of the nearby Mauna Loa; because of this, both native Hawaiians and early geologists considered it an active satellite of its more massive neighbor. However, analysis of the chemical composition of lavas from the two volcanoes shows 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.
Kīlauea | Structure
It is apparent from the ruggedness of the eroded hills that they are much older than the surrounding landscape. Most of the surface of Mauna Loa is thought to have formed within the last 4,000 years, but the Ninole Hills are estimated to be between 100,000 and 200,000 years old. During this period there seem to have been massive failures in the support of the south wall of Mauna Loa, resulting in debris landslides that removed chunks out of the volcano, revealing remnants of the older sections of Mauna Loa.
Ninole Hills | Introduction
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, deep. The first is a rift trending southwest from the caldera to the sea and a further 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 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 high Puu Ulaula, or Red Hill.
Mauna Loa | Structure
Mauna Kea last erupted 6,000 to 4,000 years ago and is now considered dormant. The peak is about higher than Mauna Loa, its more massive neighbor. In Hawaiian religion, the peaks of the island of Hawaii are sacred. An ancient law allowed only high-ranking aliʻi to visit its peak. Ancient Hawaiians living on the slopes of Mauna Kea relied on its extensive forests for food, and quarried the dense volcano-glacial basalts on its flanks for tool production. When Europeans arrived in the late 18th century, settlers introduced cattle, sheep and game animals, many of which became feral and began to damage the volcano's ecological balance.
Mauna Kea | Introduction
An eruption in 1868 occurred alongside the enormous 1868 Hawaii earthquake, a magnitude eight event that claimed 77 lives and remains the largest earthquake ever to hit the island. Following further activity in 1871, Mauna Loa experienced nearly continuous activity from August 1872 through 1877, a long-lasting and voluminous eruption lasting approximately 1,200 days and never moving beyond its summit. A short single-day eruption in 1877 was unusual in that it took place underwater, in Kealakekua Bay, and within a mile of the shoreline; curious onlookers approaching the area in boats reported unusually turbulent water and occasional floating blocks of hardened lava.
Mauna Loa | Recent history
Mauna Kea is one of five volcanoes that form the island of Hawaii, the largest and youngest island of the Hawaiian–Emperor seamount chain. Of these five hotspot volcanoes, Mauna Kea is the fourth oldest and fourth most active. It began as a preshield volcano driven by the Hawaii hotspot around one million years ago, and became exceptionally active during its shield stage until 500,000 years ago. Mauna Kea entered its quieter post-shield stage 250,000 to 200,000 years ago, and is currently dormant. Mauna Kea does not have a visible summit caldera, but contains a number of small cinder and pumice cones near its summit.
Mauna Kea | Geology
The event involved the movement of cubic meters of volcanic material. A region of 10 to 13 km (4 to 5 sq mi) of the summit was altered and populated by bus-sized pillow lava blocks, precariously perched along the outer rim of the newly formed crater. "Pele's Vents," an area on the southern side, previously considered stable, collapsed completely into a giant pit, renamed "Pele's Pit". Strong currents make submersible diving hazardous in the region.
Lōʻihi Seamount | 1996 earthquake swarm
However, the flow stopped just short of entering Pāhoa. By March 2015, the June 27 flow retreated to within 6 kilometers of Pu‘u ‘Ō‘ō, greatly reducing the threat to Pāhoa. Lava from the June 27 flow remained active in this area through the remainder of 2015.
Puʻu ʻŌʻō | 2014 – 2016: Lava flow threatens Pāhoa
Kīlauea has been active throughout its history. Since 1918, Kīlauea's only prolonged period of rest was an 18-year pause between 1934 and 1952. The bulk of Kīlauea consists of solidified lava flows, intermittent with scattered volcanic ash and tephra sourced from relatively lower-volume explosive eruptions. Much of the volcano is covered in historical flows, and 90 percent of its surface dates from the last 1,100 years. Kīlauea built itself up from the seafloor over time, and thus much of its bulk remains underwater; its subaerial surface is in the form of a gently sloping, elongate, decentralized shield with a surface area of approximately , making up 13.7 percent of the island's total surface area.
Kīlauea | Structure
Figure 4 shows seasonal and annual changes in CO concentration measured at Mauna Loa, Hawaii from 1987 to 1990. CO concentration steadily increased, but within-year variation has been greater than the annual increase since measurements began in 1957.
Ecosystem ecology | Operation
Holocene activity has included explosive eruptions ranging in size from moderate to plinian. The last major eruption took place about 3600 years ago. Lava dome growth has produced block and ash flows that traveled primarily to the NE and SE. Minor explosive eruptions have been recorded from Tolima in the 19th and 20th centuries.
Nevado del Tolima | Eruptive history
At the time this was the most energetic earthquake swarm in Hawaii recorded history. The swarm altered of the seamount's summit; one section, "Pele's Vents", collapsed entirely upon itself and formed the renamed "Pele's Pit". The volcano has remained relatively active since the 1996 swarm and is monitored by the United States Geological Survey (USGS). The Hawaii Undersea Geological Observatory (HUGO) provided real-time data on Lōʻihi between 1997 and 1998. Lōʻihi's last known eruption was in 1996, before the earthquake swarm of that summer.
Lōʻihi Seamount | Introduction
Similar activity on the northern side of Cloudcap and the eastern segment of Llao Rock that ejected dacitic tephra and pyroclastic rock also formed fused edifices. About 50,000 years ago, a vent at Mazama erupted the Watchman flow, which filled a canyon at the southwestern wall of the complex. From 50,000 to 40,000 years ago, Mazama vents continued to erupt andesite lava flows onto the northern and southwestern slopes and create dacite lava domes on the southern flanks. These domes often collapsed and produced pyroclastic flows that coursed down the southern slope of the volcano, forming deposits up to Devil's Backbone, a craggy volcanic dike that was exhumed when the volcano collapsed.
Mount Mazama | Early activity
Activity was strombolian in nature with the formation of Pele's tears and lava bombs and was likely monogenetic in nature. A fault system running through the edifice possibly controlled the activity of this volcano.
Agua Poca | Geology
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 extensive charcoal-based radiocarbon dating (perhaps the most extensive such prehistorical eruptive dating on Earth) has amassed a record of almost two hundred reliably dated extant flows confirming this hypothesis. The oldest exposed flows on Mauna Loa are thought to be the Ninole Hills on its southern flank, subaerial basalt rock dating back approximately 100 to 200 thousand years. They form a terrace against which younger flows have since banked, heavily eroded and incised against its slope in terms of direction; this is believed to be the result of a period of erosion because of a change in the direction of lava flow caused by the volcano's prehistoric slump.
Mauna Loa | Prehistoric eruptions
The increase in activity in the fall of 2005 produced an active -long lava flow, extending from the summit cone of Mount Belinda to the sea. The flow spread northeast from the volcanic vent, and then became diverted due north by an arête. By late 2007, eruptive activity had ceased, and in 2010 the only activity was from scattered fumaroles and cooling lava.
Mount Belinda | Introduction
The reserve was established in 1981. In 1998, the area leased to the Mauna Kea Observatory (called the Kea Science Reserve) was modified to exclude the Ice Age reserve. Another small parcel surrounding the rocky cinder cone called Puu Pōhaku at , contains a rare example of permafrost in the tropics. A 2004 study found the rare wēkiu bug ("Nysius wekiuicola") in the reserve.
Mauna Kea Ice Age Reserve | Location
Late Pleistocene to Holocene activity consisted of discrete episodes lasting about 10,000 years and separated by tens of thousands of years with no recognized activity. Aside from actual eruptions, various types of edifice collapse are recorded at Taapaca including sector collapses of segments of the volcano and mass failure of individual domes, which generated block-and-ash flows.
Taapaca | Eruptive activity
Mauna Loa ( or ; Hawaiian: ; ) is one of five volcanoes that form the Island of Hawaii in the U.S. state of Hawaiʻi in the Pacific Ocean. The largest subaerial volcano in both mass and volume, Mauna Loa has historically been considered the largest volcano on Earth, dwarfed only by Tamu Massif. It is an active shield volcano with relatively gentle slopes, with a volume estimated at approximately , although its peak is about lower than that of its neighbor, Mauna Kea. Lava eruptions from Mauna Loa are silica-poor and very fluid, and they tend to be non-explosive.
Mauna Loa | Introduction
Since its eruption stopped about 250,000–100,000 years ago, the period of eruptive activity was short in time. The eruptions of the cone came in three phases: a period where lava flows built up its cone, one where more explosive pyroclastic eruptions took place, and the final period, in which pyroclastic and material of lava-based origin were erupted together forming a weak cone encircled by long deposits.
Mount Thielsen | Composition
Much of the remainder of the volcano is hazard level three, about 15 to 20 percent of which has been covered by flows within the last 750 years. However, two sections of the volcano, the first in the Naalehu area and the second on the southeastern flank of Mauna Loa's rift zone, are protected from eruptive activity by local topography, and have thus been designated hazard level 6, comparable with a similarly isolated segment on Kīlauea. Although volcanic eruptions in Hawaiʻi rarely produce casualties (the only direct historical fatality due to volcanic activity on the island occurred at Kīlauea in 1924, when an unusually explosive eruption hurled rocks at an onlooker), property damage due to inundation by lava is a common and costly hazard.
Mauna Loa | Hazards
The bulk of information about Lōʻihi comes from dives made in response to the 1996 eruption. In a dive conducted almost immediately after seismic activity was reported, visibility was greatly reduced by high concentrations of displaced minerals and large floating mats of bacteria in the water. The bacteria that feed on the dissolved nutrients had already begun colonizing the new hydrothermal vents at Pele's Pit (formed from the collapse of the old ones), and may be indicators of the kinds of material ejected from the newly formed vents. They were carefully sampled for further analysis in a laboratory. An OBO briefly sat on the summit before a more permanent probe could be installed.
Lōʻihi Seamount | 1996 to present
The last eruption of Mauna Kea was about 4,600 years ago (about 2600 BC); because of this inactivity, Mauna Kea is assigned a United States Geological Survey hazard listing of 7 for its summit and 8 for its lower flanks, out of the lowest possible hazard rating of 9 (which is given to the extinct volcano Kohala). Since 8000 BC lava flows have covered 20% of the volcano's summit and virtually none of its flanks. Despite its dormancy, Mauna Kea is expected to erupt again. Based on earlier eruptions, such an event could occur anywhere on the volcano's upper flanks and would likely produce long lava flows, mostly of aā, long.
Mauna Kea | Future activity
In 1998, were transferred from the observatory lease to supplement the Mauna Kea Ice Age Reserve. The 1982 plan was replaced in 2000 by an extension designed to serve until 2020: it instituted an Office of Mauna Kea Management, designated for astronomy, and shifted the remaining to "natural and cultural preservation". This plan was further revised to address concern expressed in the Hawaiian community that a lack of respect was being shown toward the cultural value the mountain embodied to the region's indigenous people.
Mauna Kea Observatories | Origin and background
The eruption that formed Mauna Ulu began on May 24, 1969 and continued until July 22, 1974. At the time, this was the longest-lasting and most voluminous eruption on Kīlauea's flank in at least 2,200 years, lasting 1,774 days and producing 350 million cubic meters of lava. Lava flowed down the sides of the feature and large lava fountains (Including one 539.5 meter high fountain) were witnessed. The flows formed during this time period cover 44 sq. km and some lava deposits are reported to be 7.6 meters deep. The flows destroyed parts of the Chain of Craters Road, but the damage has since been repaired and the dormant cone can be now be visited.
Mauna Ulu | 1969–1974 eruption
With the exclusion of flood basalts, mature shields are the largest volcanic features on Earth: the summit of the largest subaerial volcano in the world, Mauna Loa, lies above sea level, and the volcano, over wide at its base, is estimated to contain about of basalt. The mass of the volcano is so great that it has slumped the crust beneath it a further ; accounting for this subsidence and for the height of the volcano above the sea floor, the "true" height of Mauna Loa from the start of its eruptive history is about . Mount Everest, by comparison, is in height.
Shield volcano | Structure
Mount McLoughlin's main volcanic cone has not erupted during the Holocene, with the last production of lava flows taking place between 30,000 and 20,000 years ago. The volcano is not currently monitored for activity or deformation. The closest seismic monitoring stations lie to the south near Mount Shasta and the Medicine Lake Volcano.
Mount McLoughlin | Future activity
The volcanoes follow a distinct evolutionary pattern of growth and death. The chain includes the second largest volcano on Earth, Mauna Loa, which stands above sea level and reaches a further below the waterline and into the crust, approximately of rock. Kīlauea, meanwhile, is one of the most active volcanoes on Earth, with it's most recent eruption having lasted from January 1983 to 2018.
Shield volcano | Hawaiian Islands
The lava dome had disappeared, but in early 1992, another lava dome formed, eventually reaching a size of width and height, and was accompanied by explosions. It probably started shrinking in April 1992, although the shrinkage was directly visible only in November. Small explosions accompanied the shrinkage until, by March 1993, the dome had disappeared again.
Lascar (volcano) | Historical activity
Since then, the volcano's activity has likely been as it is now, a continual stream of effusive and explosive eruptions of roughly the same pattern as its activity in the last 200 or 300 years.
Kīlauea | Setting
Mauna Loa is a volcano in Hawaii. Mauna Loa may also refer to:
Mauna Loa (disambiguation) | Introduction
The unusually large thickness of these lava flows is from them ponding and cooling against the Cordilleran Ice Sheet when it still filled valleys at lower elevations. This was the last eruptive activity at Mount Price. The Black Tusk, the oldest and most striking of the three principal volcanoes, is the glacially dissected remains of a stratovolcano that formed between 1.3 and 1.1 million years ago. Eruptions produced hornblende andesite lava flows and lithic tuffs. Prolonged erosion destroyed the original cone. The bluffs northwest, southwest and southeast of the main volcanic edifice are remains of this ancestral volcano. Renewed volcanism between 210,000 and 170,000 years ago produced hypersthene andesite lava flows, which locally terminate with precipitous thick ice-contact margins.
Canadian Cascade Arc | Southern segment
Furthermore, the last phase occurred when the extensional events continuously carried out the deformed structures from the plateau and affecting the volcanic units.
Ovda Regio | Marginal kinematic evolution
This ignimbrite reaches a thickness of and borders Laguna del Maule lake in the north. The Bobadilla caldera is centred beneath the northern shore of Laguna del Maule, and has dimensions of . The third took place 336,000years ago and produced the welded Cordon Constanza ignimbrite. The 36 rhyodacitic lava domes and flows which surround the lake were erupted from about 24individual vents. The eruptions began 25,000years ago, after the onset of deglaciation, and continued until the last such eruption approximately 2,000years ago. After deglaciation 23,000–19,000years ago, two pulses of volcanism occurred at Laguna del Maule, the first 22,500–19,000years ago and the second in the middle-late Holocene.
Laguna del Maule (volcano) | Eruptive history
Merriam cone does not have a summit crater, but rises to above the northern lake floor. Merriam cone was produced underwater, and was probably formed at the same or similar time as Wizard Island and the central platform. Mazama was last active about 4,800 years ago, when an eruption took place near Wizard Island's eastern base. This eruption took place underwater, and it produced viscous lava that created a rhyodacite lava dome, about 2,400 years after the first period of postcaldera activity. Given that Mazama has had periods of sporadic eruptions for 420,000 years, the United States Geological Survey thinks that it is "virtually certain" that Mazama will erupt again in the future.
Mount Mazama | Recent activity and potential hazards
The second and probably also the third stage were subject to glacial erosion, which together with later sector collapses resulted in the removal of much of Taapaca's edifice and the exposure of the core of the volcano.
Taapaca | Phases
Today's volcanic edifice (Tungurahua III) is constructed inside its predecessor's (Tungurahua II) caldera which collapsed about 3000 (±90) years ago. The original edifice (Tungurahua I) collapsed at the end of the Late Pleistocene.
Tungurahua | Volcanism
Less extensive eruptions continued from 14—6 million years ago. These lava flows have been extensively exposed by the erosion resulting from the Missoula Floods, which laid bare many layers of the basalt flows on the edges of the plateau along the course of Moses Coulee.
Moses Coulee | Geological setting
In late 2012 the mountain became quite active, spewing volcanic ash. In November 2012, and continuing into 2013, a 3 km exclusion zone was set up and residents living around the mountain were evacuated or moved to Maumere city on the main island of Flores. In the first 8 months of 2013 there was regular activity from the lava dome including repeated ash plumes – generally reaching altitudes of 2–3 km – dome collapses, explosions, avalanches and pyroclastic flows.
Paluweh | 2012–2013
The island of Hawaiʻi is built from five separate shield volcanoes that erupted somewhat sequentially, one overlapping the other. These are (from oldest to youngest): Geological evidence from exposures of old surfaces on the south and west flanks of Mauna Loa led to the proposal that two ancient volcanic shields (named Ninole and Kulani) were all but buried by the younger Mauna Loa. Geologists now consider these "outcrops" to be part of the earlier building of Mauna Loa. Because Mauna Loa and Kīlauea are active volcanoes, the island of Hawaii is still growing. Between January 1983 and September 2002, lava flows added to the island.
Hawaii (island) | Volcanism
There are compositional trends in the region of the volcanic arc between 33° and 42°, with more northerly volcanoes being more andesitic in composition while to the south basalts are more frequent.
Laguna del Maule (volcano) | Composition of erupted rocks
It is even more poorly known than "N. wekiuicola", but appears to be in less danger since the summit of Mauna Loa is not under threat of development. Although it receives a large number of hikers, the area is largely made up of rocky lava rather than loose cinder, and is less vulnerable to human influence.
Nysius wekiuicola | Conservation
Taranaki is geologically young, having commenced activity approximately 135,000 years ago. The most recent volcanic activity was the production of a lava dome in the crater and its collapse down the side of the mountain in the 1850s or 1860s. Between 1755 and 1800, an eruption sent a pyroclastic flow down the mountain's northeast flanks, and a moderate ash eruption occurred about 1755, of the size of Ruapehu's activity in 1995/1996. The last major eruption occurred around 1655. Recent research has shown that over the last 9,000 years minor eruptions have occurred roughly every 90 years on average, with major eruptions every 500 years.
Mount Taranaki | Volcanic activity
The volcano is thought to have last erupted about 2.5 million years ago.
Waiʻanae Range | Introduction
Later glaciations have formed moraines on the volcano.
Ollagüe | Introduction
More than half of this is under 3,000 years old, and about 12% is less than 1,000 years of age. Between the years 1700 and 2016, eruptions originated from six vents; four of these lava flows poured into the sea to the west coast.
Hualālai | History
Since the creation of an access road in 1964, thirteen telescopes funded by eleven countries have been constructed at the summit. The Mauna Kea Observatories are used for scientific research across the electromagnetic spectrum and comprise the largest such facility in the world. Their construction on a landscape considered sacred by Native Hawaiians continues to be a topic of debate to this day.
Mauna Kea | Introduction
Other groups began requesting subleases on the newly accessible mountaintop. By 1970, two telescopes had been constructed by the United States Air Force and Lowell Observatory. In 1973, Canada and France agreed to build the 3.6 m CFHT on Mauna Kea. However, local organizations started to raise concerns about the environmental impact of the observatory. This led the Department of Land and Natural Resources to prepare an initial management plan, drafted in 1977 and supplemented in 1980. In January 1982, the University of Hawaiʻi Board of Regents approved a plan to support the continued development of scientific facilities at the site.
Mauna Kea Observatories | Origin and background
After four months of volcanic earthquakes, small phreatic eruptions began on 18 September 1943, breaking through a layer of highly metamorphosed rocks, before the first major explosion occurred on 27 December 1943. Two more major explosions occurred on 13 February and 23 July 1944, creating pyroclastic flows and lahars, and leveling 80 km of forest. The eruption stopped on the final explosion on 31 August 1944. The volcano was capped with a 500 m wide, steep-walled crater that is now forested and contains a small lake.
Waiowa | 1943-1944 eruption
Eruptions on Mauna Loa are almost always preceded and accompanied by prolonged episodes of seismic activity, the monitoring of which was the primary and often only warning mechanism in the past and which remains viable today. Seismic stations have been maintained on Hawaiʻi since the Observatory's inception, but these were concentrated primarily on Kīlauea, with coverage on Mauna Loa improving only slowly through the 20th century. Following the invention of modern monitoring equipment, the backbone of the present-day monitoring system was installed on the volcano in the 1970s. Mauna Loa's July 1975 eruption was forewarned by more than a year of seismic unrest, with the HVO issuing warnings to the general public from late 1974; the 1984 eruption was similarly preceded by as much as three years of unusually high seismic activity, with volcanologists predicting an eruption within two years in 1983.
Mauna Loa | Monitoring
In the area of Laguna del Maule, the subducting Nazca plate reaches a depth of and is 37million years old. During the Late Miocene, the convergence rate was higher than today and the Malargüe fold belt formed east of the main chain in response. The Moho is found at depths of beneath the volcanic field.
Laguna del Maule (volcano) | Geology
The Reserve was established in 1968, and is leased by the State of Hawaiʻi's Department of Land and Natural Resources (DLNR). The University of Hawaiʻi manages the site and leases land to several multi-national facilities, which have invested more than $2 billion in science and technology. The lease expires in 2033 and after that 40 of 45 square kilometers (25 of 28 square miles) revert to the state of Hawaii.
Mauna Kea Observatories | Management
In pre-Columbian times, the field was a source of obsidian with regional importance. Between 2004 and 2007, ground inflation began in the volcanic field, indicating the intrusion of a sill beneath it. The rate of inflation is faster than those measured on other inflating volcanoes such as Uturunku in Bolivia and Yellowstone Caldera in the United States and has been accompanied by anomalies in soil gas emission and seismic activity. This pattern has created concern about the potential for impending large-scale eruptive activity.
Laguna del Maule (volcano) | Introduction
West Molokai Volcano, sometimes called Mauna Loa for the census-designated place, is an extinct shield volcano comprising the western half of Molokai island in the U.S. state of Hawaii.
West Molokai Volcano | Introduction
The volcano resumed natrocarbonatite lava flow which started to fill the large crater from the 2007-2008 eruption. As of July 2013, there is a large active hornito on the western edge of the crater floor. During June, residents near the volcano reported several earthquakes. The new crater is inaccessible and climbers have only occasionally glimpsed into it.
Ol Doinyo Lengai | 2013
Mount Mazama formed as a group of overlapping volcanic edifices such as shield volcanoes and small composite cones, becoming active intermittently until its climactic eruption 7,700 years ago. This eruption, the largest known within the Cascade Volcanic Arc in a million years, destroyed Mazama's summit, reducing its approximate height by about . Much of the edifice fell into the volcano's partially emptied neck and magma chamber, creating a caldera. The region's volcanic activity results from the subduction of the offshore oceanic plate, and is influenced by local extensional faulting. Mazama is dormant, but the US Geological Survey says eruptions on a smaller scale are likely, which would pose a threat to its surroundings.
Mount Mazama | Introduction
The Mazama vicinity formed gradually, its earliest deposits consisting of dacite from up to 1.28 million years ago. Between 725,000 and 500,000 years ago, rhyodacite was erupted, eventually forming a lava dome field with a volume of and dimensions of . This featured up to 40 rhyodacitic domes and lava flows, produced between 470,000 and 410,000 years ago before stratocone formation began. Mazama formed as a group of overlapping volcanic edifices, which included shield volcanoes and small composite cones. Cone-building eruptions took place within short periods of time. Shield volcanoes fed Mazama's expansion with basaltic andesite lava flows that covered large expanses on the slopes of the mountain.
Mount Mazama | Early activity