Volcanic Landslide
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A volcanic landslide or volcanogenic landslide is a type of
mass wasting Mass wasting, also known as mass movement, is a general term for the movement of rock (geology), rock or soil down slopes under the force of gravity. It differs from other processes of erosion in that the debris transported by mass wasting is no ...
that takes place at
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 ...
es.


Occurrences

All volcanic edifices are susceptible to
landslide 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. Landslides ...
s, particularly
stratovolcanoes 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 a ...
and
shield volcanoes A shield volcano is a type of volcano named for its low profile, resembling a shield lying on the ground. It is formed by the eruption of highly fluid (low viscosity) lava, which travels farther and forms thinner flows than the more viscous lava ...
where landslides are important processes. Volcanic landslides range in size from less than to more than . The largest volcanic landslides on Earth occur from
submarine volcanoes Submarine volcanoes are underwater vents or fissures in the Earth's surface from which magma can erupt. Many submarine volcanoes are located near areas of tectonic plate formation, known as mid-ocean ridges. The volcanoes at mid-ocean ridges ...
and are several times larger than those that occur on land.
Submarine landslide Submarine landslides are marine landslides that transport sediment across the continental shelf and into the deep ocean. A submarine landslide is initiated when the downwards driving stress (gravity and other factors) exceeds the resisting stres ...
s with volumes of have occurred in the
Canary Islands The Canary Islands (; ) or Canaries are an archipelago in the Atlantic Ocean and the southernmost Autonomous communities of Spain, Autonomous Community of Spain. They are located in the northwest of Africa, with the closest point to the cont ...
within the last 43 million years, but the largest submarine landslides could have been up to in volume. Massive submarine landslides have also taken place in 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 ...
over the last several million years, the largest of which constitute significant portions of the islands from which they originated. Smaller landslides have also been identified at volcanoes on
Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...
and
Venus Venus is the second planet from the Sun. It is often called Earth's "twin" or "sister" planet for having almost the same size and mass, and the closest orbit to Earth's. While both are rocky planets, Venus has an atmosphere much thicker ...
. Martian landslides reach lengths of and more whereas the largest Venusian landslides extend only about . The most dramatic landslide deposits on Venus occur beneath the slopes of volcanoes. Since erosion rates on Venus are much lower than those on Earth due to the lack of water on the surface, landslides are an important mechanism in wearing down mountain regions on Venus. The rounded hills of the complexly deformed
tessera A tessera (plural: tesserae, diminutive ''tessella'') is an individual tile, usually formed in the shape of a square, used in creating a mosaic. It is also known as an abaciscus or abaculus. Historical tesserae In early antiquity, mo ...
, or tile-like, terrain on Venus have probably been modified by numerous landslides.


Types

At volcanoes, the term landslide is commonly used for slope movements with shear and displacement in a relatively narrow zone. They can be in the form of
debris avalanche Debris flows are geological phenomena in which water-laden masses of soil and fragmented rock flow down mountainsides, funnel into stream channels, entrain objects in their paths, and form thick, muddy deposits on valley floors. They generally ...
s,
debris flow Debris flows are geological phenomena in which water-laden masses of soil and fragmented Rock (geology), rock flow down mountainsides, funnel into stream channels, entrain objects in their paths, and form thick, muddy deposits on valley floors. ...
s, slumps and
rockfall A rockfall or rock-fallWhittow, John (1984). ''Dictionary of Physical Geography''. London: Penguin, 1984. . is a quantity of Rock (geology), rock that has fallen freely from a cliff face. The term is also used for collapse of rock from roof or wa ...
s. A debris avalanche is a sudden, very rapid flow of rock and soil in response to gravity. It is a common middle stage in the transformation of a cohesive debris flow from a landslide or rockslide. Debris avalanches may be restricted to grain flows or granular flows, in which flow mechanics are governed by particle interactions involving friction and collision. Debris flows, in contrast, owe much of their behaviour to excess pore-water pressure and a pore fluid that is viscous and contains fine sediment.


Sector collapses

The largest landslides from volcanoes are called sector or edifice collapses. Prehistoric sector collapses are preserved in the
geological record The geologic record in stratigraphy, paleontology Paleontology, also spelled as palaeontology or palæontology, is the scientific study of the life of the past, mainly but not exclusively through the study of fossils. Paleontologists use ...
in the form of debris avalanche deposits and collapse scars. Debris avalanche deposits can be found up to from the site of collapse. 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. Such collapse scars, open at one end, have long been noted in many volcanic regions around the world. The largest
volcanic island Geologically, a volcanic island is an island of volcanic origin. The term high island can be used to distinguish such islands from low islands, which are formed from sedimentation or the uplifting of coral reefs (which have often formed ...
sector collapse in historic times took place in 1888 when
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 ...
collapsed off the northern coast of
Papua New Guinea Papua New Guinea, officially the Independent State of Papua New Guinea, is an island country in Oceania that comprises the eastern half of the island of New Guinea and offshore islands in Melanesia, a region of the southwestern Pacific Ocean n ...
. Edifice reconstruction generally must occur before a second sector collapse. ;Prehistoric *
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 ...
,
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 ...
collapse *
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 ...
, Ventorrillo collapse *
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 ...
, Osceola collapse ;Historic *
Mount St. Helens Mount St. Helens (known as Lawetlat'la to the local Cowlitz people, and Loowit or Louwala-Clough to the Klickitat) is an active stratovolcano located in Skamania County, Washington, in the Pacific Northwest region of the United States ...
,
1980 Events January * January 4 – U.S. President Jimmy Carter proclaims a United States grain embargo against the Soviet Union, grain embargo against the USSR with the support of the European Commission. * January 6 – Global Positioning Sys ...
*
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 ...
,
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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 Events January * January 3 – The great telescope (with an objective lens of diameter) at Lick Observatory in California is first used. * January 12 – The Schoolhouse Blizzard hits Dakota Territory and the states of Montana, M ...


Flank collapses

Flank collapses are much smaller than sector collapses, but they may also yield far-reaching debris flows. Flank collapses differ from sector collapses in that they only involve the volcano flank whereas sector collapses are large enough to involve the volcano summit. The smaller size of a flank collapse indicates that there need be no repose time before another flank collapse occurs, and hence they can be treated as random events. ;Prehistoric *
East Molokai Volcano The East Molokai Volcano, sometimes also known as Wailau for the Wailau valley on its north side, is an extinct shield volcano comprising the eastern two-thirds of the island of Molokai in the U.S. state of Hawaii. Description The East Molokai h ...
, Wailau collapse * Koʻolau Volcano, Nuʻuanu collapse *
Mount Garibaldi Mount Garibaldi (, ) is a dormant stratovolcano in the Garibaldi Ranges of the Pacific Ranges in southwestern British Columbia, Canada. It has a maximum elevation of and rises above the surrounding landscape on the east side of the Cheakamus Ri ...
, Cheekye collapse ;Historic * Mount Meager,
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Mount Elgon Mount Elgon is an extinct shield volcano on the border of Uganda and Kenya, north of Kisumu and west of Kitale. The mountain's highest point, named "Wagagai", is located entirely within Uganda.
,
2010 The year saw a multitude of natural and environmental disasters such as the 2010 Haiti earthquake, the Deepwater Horizon oil spill, and the 2010 Chile earthquake. The 2009 swine flu pandemic, swine flu pandemic which began the previous year ...
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Kīlauea Kīlauea ( , ) is an active shield volcano in the Hawaiian Islands. It is located along the southeastern shore of Hawaii (island), Hawaii Island. The volcano is between 210,000 and 280,000 years old and grew above sea level about 100,000 years ...
, Hilina Slump


Causes

Several conditions can trigger landslides at volcanoes: *Intrusion of
magma 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 ...
into a volcano *
Explosive eruption In volcanology, an explosive eruption is a volcanic eruption of the most violent type. A notable example is the 1980 eruption of Mount St. Helens. Such eruptions result when sufficient gas has dissolved under pressure within a Viscosity, viscous ...
s *Large
earthquake 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 ...
directly beneath a volcano or nearby *Saturation of the ground *
Hydrothermal alteration Metasomatism (from the Greek μετά ''metá'' "change" and σῶμα ''sôma'' "body") is the chemical alteration of a Rock (geology), rock by hydrothermal and other fluids. It is traditionally defined as metamorphism which involves a change in t ...
of
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 ...
s *Structural discontinuities *High
lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...
accumulation rates *Steep slopes


Hazards

Large landslides from volcanoes often bury valleys with tens to hundreds of metres of rock debris, forming a chaotic landscape marked by dozens of small hills and closed depressions. If the landslide deposit is thick enough, it may dam streams to form lakes. These lakes may eventually drain catastrophically to create
flood A flood is an overflow of water (list of non-water floods, or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are of significant con ...
s and
lahar A lahar (, from ) is a violent type of mudflow or debris flow composed of a slurry of Pyroclastic rock, pyroclastic material, rocky debris and water. The material flows down from a volcano, typically along a valley, river valley. Lahars are o ...
s downstream. Landslides that remove a large portion of a
volcanic cone Volcanic cones are among the simplest volcanic landforms. They are built by ejecta from a volcanic vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, depending upon the nature and s ...
may abruptly decrease pressure on shallow magmatic and hydrothermal systems, which can generate explosions ranging from a small steam explosion to large steam and magma-driven directed blasts. These result in
tephra Tephra is fragmental material produced by a Volcano, volcanic eruption regardless of composition, fragment size, or emplacement mechanism. Volcanologists also refer to airborne fragments as pyroclasts. Once clasts have fallen to the ground, ...
and
ash fall Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, produced during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to re ...
hazards for surrounding areas. Large horseshoe-shaped craters formed by landslides at volcanoes will likely direct subsequent lava flows,
pyroclastic flow A pyroclastic flow (also known as a pyroclastic density current or a pyroclastic cloud) is a fast-moving current of hot gas and volcanic matter (collectively known as tephra) that flows along the ground away from a volcano at average speeds of b ...
s or lahars toward its breached opening if the primary eruptive vent is located within these deep craters. The collapse of island or coastal volcanoes from giant landslides can generate
tsunamis 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, la ...
that could potentially devastate large areas of coastal land.


Disasters

Historically, the most deadly volcanic landslide occurred in 1792 when sliding debris from Mount Mayuyama in Japan slammed into the
Ariake Sea The is a body of salt water surrounded by Fukuoka, Saga, Nagasaki, and Kumamoto Prefectures, all of which lie on the island of Kyūshū in Japan. It is the largest bay in Kyūshū. Its deepest point is only about 50 meters (165 ft) deep, and ext ...
and generated a tsunami that reached the opposite shore; nearly 15,000 people were killed. The sector collapse of Ritter Island in 1888 generated a tsunami with runups of up to that caused damage more than away and killed anywhere between 500 and 3,000 people on neighbouring islands. A landslide originating from Devastation Glacier on the southern flank of the
Mount Meager massif The Mount Meager massif is a group of volcanic peaks in the of the Coast Mountains in southwestern British Columbia, Canada. Part of the Cascade Volcanic Arc of western North America, it is located north of Vancouver at the northern end of the P ...
in
British Columbia British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...
, Canada, buried and killed a group of four geologists at the confluence of Devastation Creek and
Meager Creek Meager Creek is a creek in the southern Pacific Ranges of the Coast Mountains in British Columbia, Canada. It flows northeast into the Lillooet River approximately northwest of the village of Pemberton and is adjacent to the Upper Lillooet Pr ...
in July 1975. In 1979, a landslide from the Indonesian volcano
Iliwerung Iliwerung or Illiwerung is a complex volcano forming a prominent south-facing peninsula on Lembata Island in southern Indonesia. It contains north-south and northwest-southeast trending lines of craters and lava domes, with the summit dome havin ...
produced waves that killed more than 500 people. In December 2018, another landslide-induced tsunami took place in Indonesia's
Sunda Strait The Sunda Strait () is the strait between the Indonesian islands of Java island, Java and Sumatra. It connects the Java Sea with the Indian Ocean. Etymology The strait takes its name from the Sunda Kingdom, which ruled the western portion of Ja ...
following a collapse of
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 ...
. The waves struck about of coastline with various heights, killing at least 373 people and damaging many buildings.


See also

*
List of landslides This list of landslides is a list of notable landslides and mudflows divided into sections by date and type. This list may be incomplete as there is no central catalogue for landslides, although it does exist for some for individual countries or ...


References


External links

*{{Commons category-inline, Volcanic landslides