A sector collapse or lateral collapse is the structural failure and subsequent collapse of a minimum volume of of a

volcano A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most oft ...

. Unlike smaller flank collapses, a sector collapse can involve the central

volcanic pipe Volcanic pipes or volcanic conduits are subterranean geology, geological structures formed by the violent, supersonic eruption of deep-origin volcanoes. They are considered to be a type of ''diatreme''. Volcanic pipes are composed of a deep, narro ...

and historically this term had been restricted by some writers to such events in arc

stratovolcano A stratovolcano, also known as a composite volcano, is a typically conical volcano built up by many alternating layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with ...

es, but is now used for large events in any volcano. Sector collapses are one of the most hazardous volcanic events, often resulting in lateral blasts,

landslides Landslides, also known as landslips, rockslips or rockslides, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, mudflows, shallow or deep-seated slope failures and debris flows. Landslide ...

, and changes in volcanic eruptive behavior. Sector collapse can be caused by

earthquakes An earthquakealso called a quake, tremor, or tembloris the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they c ...

, volcanic eruptions, gradual volcanic deformation, and other processes. Sector collapse events can occur on volcanoes at convergent and divergent

plate boundaries Plate tectonics (, ) is the scientific theory that the Earth's lithosphere comprises a number of large tectonic plates, which have been slowly moving since 3–4 billion years ago. The model builds on the concept of , an idea developed durin ...

. Sector collapses are generally very sudden; however, some attempts have been made to predict collapse events.

Causes

Internal

Sector collapse can result from internal volcanic processes. Volcanic eruption can damage originally stable magma chambers, causing a portion of the volcano to collapse. While eruption is one cause, sector collapse can occur without any eruption.

Magmatic Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...

intrusions can also lead to sector collapse.

Dikes Dyke or dike may refer to: General uses * Dyke (slang), a slang word meaning "lesbian" * Dike (geology), formations of magma or sediment that cut through and across the layering of adjacent rocks * Dike (mythology), ''Dikē'', the Greek goddess ...

fracture and deform rock, leaving the volcano weaker and more susceptible to collapse. Hydrothermal activity is another internal cause, likely due to reactions of

acid An acid is a molecule or ion capable of either donating a proton (i.e. Hydron, hydrogen cation, H+), known as a Brønsted–Lowry acid–base theory, Brønsted–Lowry acid, or forming a covalent bond with an electron pair, known as a Lewis ...

sulfates The sulfate or sulphate ion is a Polyatomic ion, polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salt (chemistry), ...

weakening

volcanic rock Volcanic rocks (often shortened to volcanics in scientific contexts) are rocks formed from lava erupted from a volcano. Like all rock types, the concept of volcanic rock is artificial, and in nature volcanic rocks grade into hypabyssal and me ...

. Gravity-induced collapse occurs when the volcanic slope approaches the critical angle of repose. The slope angle is a major factor in collapse events.

External

Sector collapse sometimes occurs because of external processes.

Seismic activity An earthquakealso called a quake, tremor, or tembloris the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they ...

is a prominent cause of collapse events. Earthquakes can weaken the structural stability of volcanoes, leading to sudden collapse or contributing to a later collapse. Intense

weather Weather is the state of the atmosphere, describing for example the degree to which it is hot or cold, wet or dry, calm or stormy, clear or cloud cover, cloudy. On Earth, most weather phenomena occur in the lowest layer of the planet's atmo ...

and heavy

rainfall Rain is a form of precipitation where water droplets that have condensed from atmospheric water vapor fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. ...

can cause damaging erosion, increasing likelihood of collapse. Glacial melting is another external cause of sector collapse, with the majority of glacial melt induced collapses occurring during the

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

. Glacial melting increases volcanic slope and decreases

pore pressure Pore water pressure (sometimes abbreviated to pwp) refers to the pressure of groundwater held within a soil or rock, in gaps between particles ( pores). Pore water pressures below the phreatic level of the groundwater are measured with piezometers ...

, leading to sector collapse. Sea level change has also been associated with sector collapse.

Predicting sector collapse

Because sector collapse events occur suddenly and over small time periods, they are difficult to predict. More often, volcanoes are assessed for risk of sector collapse. Collapse ultimately occurs due to structural instability, which can be determined by volcanic slope angle, composition of the volcano, deformation, and other factors.

Consequences

Changes to volcanic systems

Some volcanoes experience no changes in volcanic behavior while others experience altered rates of eruption and magma composition. Collapse is typically followed by

phreatic eruption A phreatic eruption, also called a phreatic explosion, ultravulcanian eruption or steam-blast eruption, occurs when magma heats ground water or surface water. The extreme temperature of the magma (anywhere from ) causes near-instantaneous evap ...

due to a reduction in

magma chamber A magma chamber is a large pool of liquid rock beneath the surface of the Earth. The molten rock, or magma, in such a chamber is less dense than the surrounding country rock, which produces buoyant forces on the magma that tend to drive it u ...

pressure after sector collapse. Damage caused by collapse can create a new and different volcanic plumbing system, which could impact eruption rates. Sector collapse often results in eruption of more

mafic A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks include ...

magma. Large overlying surface mass and the denser nature of mafic magma often prevents its rise. Collapse relieves some of the overlying surface mass thus allowing for more mafic magma composition.

Human impacts

Sector collapses and landslides caused by them have directly resulted in more than 3,500 fatalities since 1600 and caused extensive property damage. A particularly deadly consequence of sector collapse is

tsunami A tsunami ( ; from , ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and underwater explosions (including detonations, ...

. The Oshima-Oshima collapse led to a tsunami that killed 1,500 people. Sector collapse events can also displace thousands and cause

homelessness Homelessness, also known as houselessness or being unhoused or unsheltered, is the condition of lacking stable, safe, and functional housing. It includes living on the streets, moving between temporary accommodation with family or friends, liv ...

Identifying sector collapse

Prehistoric Prehistory, also called pre-literary history, is the period of human history between the first known use of stone tools by hominins million years ago and the beginning of recorded history with the invention of writing systems. The use o ...

sector collapses are stored in the geological record in the form of debris avalanche deposits and collapse scars. Debris avalanche deposits are found typically up to from the site of collapse, but in the case of the

Hawaiian islands The Hawaiian Islands () are an archipelago of eight major volcanic islands, several atolls, and numerous smaller islets in the Pacific Ocean, North Pacific Ocean, extending some from the Hawaii (island), island of Hawaii in the south to nort ...

away. Studying avalanche deposits informs on the time scale of the collapse and the volcano from which it originated. Collapse scars are also an indicator of sector collapse and are often described as "

amphitheatre An amphitheatre (American English, U.S. English: amphitheater) is an open-air venue used for entertainment, performances, and sports. The term derives from the ancient Greek ('), from ('), meaning "on both sides" or "around" and ('), meani ...

" or "

horseshoe A horseshoe is a product designed to protect a horse hoof from wear. Shoes are attached on the palmar surface (ground side) of the hooves, usually nailed through the insensitive hoof wall that is anatomically akin to the human toenail, altho ...

" shaped. One such collapse scar is the

Sciara del Fuoco Sciara del Fuoco is a Scree, talus scree or depression located on Stromboli, Stromboli Island in Italy. It runs along the island's northern flank and is bounded by two ridges. It now serves as a major tourist attraction on the island. Formation ...

formed on the Stromboli volcano due to a sector collapse.

Examples

Prehistoric

* Antuco *

Chimborazo Chimborazo () is a stratovolcano situated in Ecuador in the Cordillera Occidental (Ecuador), Cordillera Occidental range of the Andes. Its last known Types of volcanic eruptions, eruption is believed to have occurred around AD 550. Although not ...

Popocatépetl Popocatépetl ( , , ; ) is an active stratovolcano located in the states of Puebla, Morelos, and Mexico in central Mexico. It lies in the eastern half of the Trans-Mexican Volcanic Belt. At it is the second highest peak in Mexico, after Ci ...

Mount Rainier Mount Rainier ( ), also known as Tahoma, is a large active stratovolcano in the Cascade Range of the Pacific Northwest in the United States. The mountain is located in Mount Rainier National Park about south-southeast of Seattle. With an off ...

Mount Shasta Mount Shasta ( ; Shasta people, Shasta: ''Waka-nunee-Tuki-wuki''; Karuk language, Karuk: ''Úytaahkoo'') is a Volcano#Volcanic activity, potentially active stratovolcano at the southern end of the Cascade Range in Siskiyou County, California. A ...

Shiveluch Shiveluch ( rus, Шивелуч, p=ʂɨˈvʲeɫʊt͡ɕ), also called Sheveluch, which originates from the name "suelich" which means "smoking mountain" in Itelmen is the northernmost active volcano in Kamchatka Krai, Russia. It and Karymsky a ...

Stromboli Stromboli ( , ; ) is an island in the Tyrrhenian Sea, off the north coast of Sicily, containing Mount Stromboli, one of the four active volcanoes in Italy. It is one of the seven Aeolian Islands, a volcanic arc north of Sicily, and the mytho ...

Historic

Anak Krakatoa Anak KrakatauEnglish translation and common name: ''Child of Krakatoa'' is a volcanic island in Indonesia. On 29 December 1927, Anak Krakatau first emerged from the caldera formed in 1883 by the explosive volcanic eruption that destroyed the ...

2018 Events January * January 1 – Bulgaria takes over the Presidency of the Council of the European Union, after the Estonian presidency. * January 4 – SPLM-IO rebels loyal to Chan Garang Lual start a raid against Juba, capital of ...

Mount Bandai is a stratovolcano located in Inawashiro-town, Bandai-town, and Kitashiobara village, in Yama-Gun, Fukushima prefecture. It is an active stratovolcano located to the north of Lake Inawashiro. Mount Bandai, including the Bandai heights, belo ...

, 1888 *

Bezymianny Bezymianny ( ''Bezymyannyyi'', meaning ''unnamed'') is an active stratovolcano in Kamchatka Peninsula, Kamchatka, Russia. Bezymianny volcano had been considered extinct until 1955. Activity started in 1955, culminating in a dramatic eruption on 3 ...

, 1956 * Oshima-Oshima,

1741 Events January–March * January 13 ** Lanesborough, Massachusetts is created as a township. ** Conventicle Act of 1741 is introduced in Denmark-Norway. *February 13 – Sir Robert Walpole, the Prime Minister of Great Britain ...

Ritter Island Ritter Island is a small crescent-shaped volcanic island north-east of New Guinea, situated between Umboi Island and Sakar Island. There are several recorded eruptions of this basaltic-andesitic stratovolcano prior to a spectacular lateral co ...

, 1888: largest historical collapse * Mount St. Helens, 1980

References

{{reflist Volcanoes Geology terminology