A volcanic tsunami, also called a volcanogenic tsunami, is a

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, ...

produced by volcanic phenomena. About 20–25% of all fatalities at volcanoes during the last 250 years have been caused by volcanic tsunamis. The most devastating volcanic tsunami in recorded history was that produced by the

1883 eruption of Krakatoa Beginning on 20 May 1883, and ending on 21 October 1883, the volcanic island of Krakatoa, located in the Sunda Strait, had repeated, months long Types of volcanic eruptions, volcanic eruptions. The most destructive of these eruptions occurred o ...

. The waves reached heights of and killed 36,000 people.

Causes

A wide variety of volcanic processes can produce tsunamis. This includes volcanic

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 ...

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the str ...

collapse, explosive

submarine eruption Submarine eruptions are volcano eruptions which take place beneath the surface of water. These occur at constructive margins, subduction zones, and within tectonic plates due to hotspots. This eruption style is far more prevalent than subaerial ...

s, the effects of

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 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 on water, base surges with accompanying

shock wave In physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a me ...

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 ...

avalanching into the sea, air waves from explosive

subaerial eruption In volcanology, a subaerial eruption is any sort of volcanic eruption that occurs on the land surface, or in the open air "under the air". They generally produce pyroclastic flows, lava fountains and lava flows, which are commonly classified in di ...

s, avalanches of cold rock, and avalanches of hot material. Volcanic tsunamis produced by large lateral collapse

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 and ocean-entering pyroclastic flows are the largest and most hazardous.

Volcanic eruptions

Pyroclastic flows can cause tsunamis as a result of them interacting with waterbodies, although the conditions required to generate a tsunami and the mechanisms of interaction between pyroclastic flows and water remain partially elusive. This is because theoretical studies of this complex phenomenon are rare and observations by the scientific community are scarce. It has been demonstrated by Watts and Waythomas (2003) that the dense, basal

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. ...

component of a pyroclastic flow produces the most energetic and coherent water waves. Smaller waves are theoretically generated by pressure impulses and steam explosions, as well as flow pressure and shear. Discharge rate, transport distance from a volcanic vent, angle of incidence, bulk density of the flow and its preservation or disaggregation underwater are important parameters controlling the interactions between pyroclastic flows and bodies of water. Tsunamis were created by pyroclastic flows from the eruptions of Tambora (1815), Mount Ruang (1871), Krakatoa (1883), Mount Pelée (1902) and Rabaul Volcano (1994). Tsunamis generated by underwater volcanic explosions depend on the energy and water depth of the explosion. An underwater explosion resulting in the formation of a

crater A crater is a landform consisting of a hole or depression (geology), depression on a planetary surface, usually caused either by an object hitting the surface, or by geological activity on the planet. A crater has classically been described ...

can cause subsequent expansion, rise and gravitational collapse to create

tidal bore A tidal bore, often simply given as bore in context, is a tidal phenomenon in which the leading edge of the incoming tide forms a wave (or waves) of water that travels up a river or narrow bay, reversing the direction of the river or bay's cu ...

s, as well as smaller waves. Most waves caused by underwater volcanic explosions have small amplitudes, an exception being those produced by the 1996 eruption of

Karymsky Lake Karymsky Lake () is a volcanic crater lake located in the Akademia Nauk volcano on the Kamchatka Peninsula, Russia. On midnight of 2 January 1996, Akademia Nauk and Karymsky Lake erupted. Eruptive pulses from the bottom of Karymsky Lake ejected ...

in Russia which reached heights of up to or more. Although underwater volcanic explosions can generate tsunamis, many are not tsunamigenic. This is especially true for Surtseyan-type

phreatomagmatic eruption Phreatomagmatic eruptions are volcanic eruptions resulting from interaction between magma and water. They differ from exclusively magmatic eruptions and phreatic eruptions. Unlike phreatic eruptions, the products of phreatomagmatic eruptions cont ...

s, which are the result of complex

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 ...

-water interactions. Potentially more tsunamigenic are violent steam explosions that result in the formation of

maar A maar is a broad, low-relief volcanic crater caused by a phreatomagmatic eruption (an explosion which occurs when groundwater comes into contact with hot lava or magma). A maar characteristically fills with water to form a relatively shallow ...

s and

tuff ring Phreatomagmatic eruptions are volcanic eruptions resulting from interaction between magma and water. They differ from exclusively magmatic eruptions and phreatic eruptions. Unlike phreatic eruptions, the products of phreatomagmatic eruptions cont ...

s. Tsunamis produced by volcanic shock waves is a rare phenomenon, involving pressure from an

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 ...

that must be high enough to excite free waves in the atmosphere. Such volcanic tsunamis took place during the 1883 eruption of Krakatoa, the 1956 eruption of

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 ...

and the 2022 eruption of Hunga Tonga–Hunga Ha'apai. Shock wave-induced volcanic tsunamis may have also occurred during the

Hatepe eruption The Hatepe eruption, named for the Hatepe Plinian pumice tephra layer, sometimes referred to as the Taupō eruption or Horomatangi Reef Unit Y eruption, is dated to 232 CE ± 10 and was Taupō Volcano's most recent major eruption. It is ...

of Taupō Volcano around 200 CE. Underwater caldera collapse resulting from large explosive eruptions can cause tsunamis due to subsidence of the water surface. Volcanic tsunamis caused by caldera collapse may have occurred during the

Minoan eruption The Minoan eruption was a catastrophic volcanic eruption that devastated the Aegean island of Thera (also called Santorini) circa 1600 BCE. It destroyed the Minoan settlement at Akrotiri, as well as communities and agricultural areas on near ...

Santorini Santorini (, ), officially Thira (, ) or Thera, is a Greek island in the southern Aegean Sea, about southeast from the mainland. It is the largest island of a small, circular archipelago formed by the Santorini caldera. It is the southern ...

in 1638 BCE, the 1650 eruption of Kolumbo and the 1883 eruption of Krakatoa.

Volcanic earthquakes

Tsunamis caused by earthquakes preceding or during volcanic eruptions are poorly documented. Such earthquakes can be volcano-tectonic or purely tectonic in origin. Volcano-tectonic earthquakes are caused by the movement of magma beneath the surface, which results in pressure changes where the rock around the magma has experienced stress. They occur as

earthquake swarm In seismology, an earthquake swarm is a sequence of seismic events occurring in a local area within a relatively short period. The time span used to define a swarm varies, but may be days, months, or years. Such an energy release is different fr ...

s and are capable of producing small-magnitude tsunamis. Volcano-tectonic earthquakes typically have magnitudes of less than 6 on the surface-wave scale and often precede volcanic eruptions. The 1878 and 1937 eruptions of Rabaul Volcano in Papua New Guinea were reportedly preceded by tsunamis caused by an initial earthquake. Tsunamis caused by volcano-tectonic earthquakes have also occurred at

Mount Yasur Mount Yasur is a volcano on Tanna Island, Vanuatu, high above sea level, on the coast near Sulphur Bay, northeast of the taller Mount Tukosmera, which was active in the Pleistocene. It has a largely unvegetated pyroclastic cone with a nearl ...

in 1878, Mount Okmok in 1878 and Kharimkotan in 1933. Earthquakes caused by tectonic processes at volcanoes are also known to cause tsunamis. Such earthquakes can reach magnitudes greater than 6 and may occur on large

thrust fault A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks. Thrust geometry and nomenclature Reverse faults A thrust fault is a type of reverse fault that has a dip of 45 degrees or less. I ...

s at the base of volcanic edifices. For example, a M_s 7.2 earthquake in

Hawaii Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...

associated with large-scale

slumping Slumping is a technique in which items are made in a kiln by means of shaping glass over molds at high temperatures. The slumping of a pyrometric cone is often used to measure temperature in a kiln. Technique Slumping glass is a highly techni ...

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 ...

's southern submarine flank caused the 1975 Kalapana tsunami.

Slope instabilities

The slopes of many volcanoes are naturally unstable due to magmatic

intrusion In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and com ...

s, structural discontinuities, high lava accumulation rates and

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 ...

. Slope failures of volcanic edifices produce a wide spectrum of instability phenomena ranging from

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 and small landslides to large debris avalanches. The impact of debris sweeping into a waterbody can produce an impulsive wave which then propagates away from the source. Slope instabilities at volcanoes have accounted for 1% of tsunamis observed since the 17th century. Tsunamis caused by slope instabilities occurred at

Hokkaido Koma-ga-take , also , , or just is a andesitic stratovolcano on the border between Mori, Shikabe, and Nanae, all within the Oshima Subprefecture of Hokkaidō, Japan. Occurrence of volcanic activity started some 30,000 years ago. Following roughly 5,000 ...

in 1640,

Mount Unzen is an active volcanic group of several overlapping stratovolcanoes, near the city of Shimabara, Nagasaki on the island of Kyushu, Japan's southernmost main island. In 1792, the collapse of one of its several lava domes triggered a megatsuna ...

1792 Events January–March * January 9 – The Treaty of Jassy ends the Russian Empire's war with the Ottoman Empire over Crimea. * January 25 – The London Corresponding Society is founded. * February 18 – Thomas Holcrof ...

Augustine Volcano Augustine Volcano (Sugpiaq language, Sugpiaq: ''Utakineq''; Denaʼina language, Dena'ina: ''Chu Nula'') is a stratovolcano in Alaska consisting of a central complex of summit lava domes and flows surrounded by an apron of tephra, pyroclasti ...

in 1883,

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 ...

in 1888, Paluweh in 1928, Iliwerung in

1979 Events January * January 1 ** United Nations Secretary-General Kurt Waldheim heralds the start of the ''International Year of the Child''. Many musicians donate to the ''Music for UNICEF Concert'' fund, among them ABBA, who write the song ...

, Mount St. Helens in 1980,

Vulcano Vulcano () or Vulcan is a small volcanic island belonging to Italy in the Tyrrhenian Sea, about north of Sicily and located at the southernmost end of the seven Aeolian Islands. The island is known for its volcanic activity and contains severa ...

in 1988,

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 ...

2002 The effects of the September 11 attacks of the previous year had a significant impact on the affairs of 2002. The war on terror was a major political focus. Without settled international law, several nations engaged in anti-terror operation ...

and

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 ...

. Some geologists claim that large landslides from volcanic islands may be able to generate

megatsunami A megatsunami is an incredibly large wave created by a substantial and sudden displacement of material into a body of water. Megatsunamis have different features from ordinary tsunamis. Ordinary tsunamis are caused by underwater tectonic activi ...

s that can cross oceans, e.g.

Cumbre Vieja The Cumbre Vieja (; meaning "Old Summit") is an active Complex volcano, volcanic ridge on the island of La Palma in the Canary Islands, Spain. The spine of Cumbre Vieja trends in an approximate north–south direction, comprising the southern ha ...

La Palma La Palma (, ), also known as ''La isla bonita'' () and historically San Miguel de La Palma, is the most northwesterly island of the Canary Islands, a Spanish autonomous community and archipelago in Macaronesia in the North Atlantic Ocean. La Pa ...

( Cumbre Vieja tsunami hazard) 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 ...

, but this is disputed by many others.

Limnic eruptions

Limnic eruptions are a very rare phenomenon involving sudden discharges of

volcanic gas Volcanic gases are gases given off by active (or, at times, by dormant) volcanoes. These include gases trapped in cavities (Vesicular texture, vesicles) in volcanic rocks, dissolved or dissociated gases in magma and lava, or gases emanating from ...

es from deep lake waters. These discharges can cause large water displacements in lakes, triggering lake tsunamis.

Lake Nyos Lake Nyos ( ) is a crater lake in the Northwest Region of Cameroon, located about northwest of Yaoundé, the capital. Nyos is a deep lake high on the flank of an inactive volcano in the Oku volcanic plain along the Cameroon line of volcan ...

, a

volcanic crater lake A volcanic crater lake is a lake in a volcanic crater, crater that was formed by explosive eruption, explosive activity or a caldera, collapse during a types of volcanic eruptions, volcanic eruption. Formation Lakes in calderas fill large crate ...

in Cameroon, underwent a limnic eruption on 21 August 1986 when a large amount of

carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...

overturned in the lake. The eruption spawned a wave of at least that swept the shore on one side.

References