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.

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 ...

volcanic eruption A volcanic eruption occurs when material is expelled from a volcanic vent or fissure. Several types of volcanic eruptions have been distinguished by volcanologists. These are often named after famous volcanoes where that type of behavior h ...

s and

underwater explosion An underwater explosion (also known as an UNDEX) is a explosive material, chemical or nuclear explosive, nuclear explosion that occurs under the surface of a body of water. While useful in anti-ship and submarine warfare, underwater bombs are not ...

s (including detonations,

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, glacier calvings, meteorite impacts and other disturbances) above or below water all have the potential to generate a tsunami. Unlike normal ocean waves, which are generated by wind, or

tide Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide tables ...

s, which are in turn generated by the

gravitational pull In physics, gravity (), also known as gravitation or a gravitational interaction, is a fundamental interaction, a mutual attraction between all massive particles. On Earth, gravity takes a slightly different meaning: the observed force be ...

of the

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

and the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

, a tsunami is generated by the displacement of water from a large event. Tsunami waves do not resemble normal undersea currents or

sea waves In fluid dynamics, a wind wave, or wind-generated water wave, is a surface wave that occurs on the free surface of bodies of water as a result of the wind blowing over the water's surface. The contact distance in the direction of the wind is k ...

because their

wavelength In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats. In other words, it is the distance between consecutive corresponding points of the same ''phase (waves ...

is far longer. Rather than appearing as a

breaking wave In fluid dynamics and nautical terminology, a breaking wave or breaker is a wave with enough energy to "break" at its peak, reaching a critical level at which linear energy transforms into wave turbulence energy with a distinct forward curve. ...

, a tsunami may instead initially resemble a rapidly rising

. For this reason, it is often referred to as a tidal wave, although this usage is not favoured by the scientific community because it might give the false impression of a causal relationship between tides and tsunamis. Tsunamis generally consist of a series of waves, with

period Period may refer to: Common uses * Period (punctuation) * Era, a length or span of time *Menstruation, commonly referred to as a "period" Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (o ...

s ranging from minutes to hours, arriving in a so-called "

wave train In physics, a wave packet (also known as a wave train or wave group) is a short burst of localized wave action that travels as a unit, outlined by an envelope. A wave packet can be analyzed into, or can be synthesized from, a potentially-infini ...

". Wave heights of tens of metres can be generated by large events. Although the impact of tsunamis is limited to coastal areas, their destructive power can be enormous, and they can affect entire ocean basins. The

2004 Indian Ocean tsunami On 26 December 2004, at 07:58:53 local time (UTC+07:00, UTC+7), a major earthquake with a magnitude of 9.2–9.3 struck with an epicenter, epicentre off the west coast of Aceh in northern Sumatra, Indonesia. The Submarine earthquake, undersea ...

was among the deadliest natural disasters in human history, with at least 230,000 people killed or missing in 14 countries bordering the

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or approximately 20% of the water area of Earth#Surface, Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia (continent), ...

. The

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

historian

Thucydides Thucydides ( ; ; BC) was an Classical Athens, Athenian historian and general. His ''History of the Peloponnesian War'' recounts Peloponnesian War, the fifth-century BC war between Sparta and Athens until the year 411 BC. Thucydides has been d ...

suggested in his 5th century BC ''

History of the Peloponnesian War The ''History of the Peloponnesian War'' () is a historical account of the Peloponnesian War (431–404 BC), which was fought between the Peloponnesian League (led by Sparta) and the Delian League (led by Classical Athens, Athens). The account, ...

'' that tsunamis were related to

submarine earthquake A submarine, undersea, or underwater earthquake is an earthquake that occurs underwater at the seabed, bottom of a body of water, especially an ocean. They are the leading cause of tsunamis. The magnitude can be measured scientifically by the use ...

s, but the understanding of tsunamis remained slim until the 20th century, and much remains unknown. Major areas of current research include determining why some large earthquakes do not generate tsunamis while other smaller ones do. This ongoing research is designed to help accurately forecast the passage of tsunamis across oceans as well as how tsunami waves interact with shorelines.

Terminology

Tsunami

The term "tsunami" is a borrowing from the Japanese , meaning 'harbour wave'. For the plural, one can either follow ordinary English practice and add an ''s'', or use an invariable plural as in the Japanese. Some English speakers alter the word's initial to an by dropping the "t," since English does not natively permit at the beginning of words, though the original Japanese pronunciation is . The term has become commonly accepted in English, although its literal Japanese meaning is not necessarily descriptive of the waves, which do not occur only in harbours.

Tidal wave

Tsunamis are sometimes referred to as ''tidal waves''. This once-popular term derives from the most common appearance of a tsunami, which is that of an extraordinarily high

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 ...

. Tsunamis and tides both produce waves of water that move inland, but in the case of a tsunami, the inland movement of water may be much greater, giving the impression of an incredibly high and forceful tide. In recent years, the term "tidal wave" has fallen out of favour, especially in the scientific community, because the causes of tsunamis have nothing to do with those of

s, which are produced by the gravitational pull of the moon and sun rather than the displacement of water. Although the meanings of "tidal" include "resembling" or "having the form or character of" tides, use of the term ''tidal wave'' is discouraged by geologists and oceanographers. A 1969 episode of the TV crime show ''

Hawaii Five-O Hawaii Five-O or Hawaii Five-0 may refer to: * ''Hawaii Five-0'' (2010 TV series), an American action police procedural television series * ''Hawaii Five-O'' (1968 TV series), an American police procedural drama series produced by CBS Productio ...

'' entitled "Forty Feet High and It Kills!" used the terms "tsunami" and "tidal wave" interchangeably.

Seismic sea wave

The term ''seismic sea wave'' is also used to refer to the phenomenon because the waves most often are generated by

seismic Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes (or generally, quakes) and the generation and propagation of elastic ...

activity such as earthquakes. Prior to the rise of the use of the term ''tsunami'' in English, scientists generally encouraged the use of the term ''seismic sea wave'' rather than ''tidal wave''. However, like ''tidal wave'', ''seismic sea wave'' is not a completely accurate term, as forces other than earthquakes—including underwater

s, volcanic eruptions, underwater explosions, land or ice

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 ...

into the ocean,

meteorite A meteorite is a rock (geology), rock that originated in outer space and has fallen to the surface of a planet or Natural satellite, moon. When the original object enters the atmosphere, various factors such as friction, pressure, and chemical ...

impacts, and the weather when the atmospheric pressure changes very rapidly—can generate such waves by displacing water.

Other terms

The use of the term ''tsunami'' for waves created by landslides entering bodies of water has become internationally widespread in both scientific and popular literature, although such waves are distinct in origin from large waves generated by earthquakes. This distinction sometimes leads to the use of other terms for landslide-generated waves, including ''landslide-triggered tsunami'', ''displacement wave'', ''non-seismic wave'', ''impact wave'', and, simply, ''giant wave''. A tsunami which cannot be linked to an earthquake is sometimes termed an "orphan tsunami". This may happen in the case of tsunamis caused in the distant past, before international communications, by earthquakes far away, such as a tsunami in Japan caused by an earthquake in the Americas.

History

Japan has the longest

recorded history Recorded history or written history describes the historical events that have been recorded in a written form or other documented communication which are subsequently evaluated by historians using the historical method. For broader world h ...

of tsunamis. As early as 426 BC the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

historian

inquired in his book ''

'' about the causes of tsunami, and was the first to argue that ocean earthquakes must be the cause.

“A History of the Peloponnesian War”, 3.89.1–4
/ref> The oldest human record of a tsunami dates back to

479 BC __NOTOC__ Year 479 BC was a year of the pre-Julian Roman calendar. At the time, it was known as the Year of the Consulship of Vibulanus and Rutilus (or, less frequently, year 275 ''Ab urbe condita''). The denomination 479 BC for this year has b ...

, in the Greek colony of

Potidaea __NOTOC__ Potidaea (; , ''Potidaia'', also Ποτείδαια, ''Poteidaia'') was a colony founded by the Corinthians around 600 BC in the narrowest point of the peninsula of Pallene, Chalcidice, Pallene, the westernmost of three peninsulas at t ...

, thought to be triggered by an earthquake. The tsunami may have saved the colony from an invasion by the

Achaemenid Empire The Achaemenid Empire or Achaemenian Empire, also known as the Persian Empire or First Persian Empire (; , , ), was an Iranian peoples, Iranian empire founded by Cyrus the Great of the Achaemenid dynasty in 550 BC. Based in modern-day Iran, i ...

The cause, in my opinion, of this phenomenon must be sought in the earthquake. At the point where its shock has been the most violent the sea is driven back, and suddenly recoiling with redoubled force, causes the inundation. Without an earthquake I do not see how such an accident could happen.
Thucydides Thucydides ( ; ; BC) was an Classical Athens, Athenian historian and general. His ''History of the Peloponnesian War'' recounts Peloponnesian War, the fifth-century BC war between Sparta and Athens until the year 411 BC. Thucydides has been d ...

“A History of the Peloponnesian War”, 3.89.5
/ref>

The

Roman Roman or Romans most often refers to: *Rome, the capital city of Italy *Ancient Rome, Roman civilization from 8th century BC to 5th century AD *Roman people, the people of Roman civilization *Epistle to the Romans, shortened to Romans, a letter w ...

historian

Ammianus Marcellinus Ammianus Marcellinus, occasionally anglicized as Ammian ( Greek: Αμμιανός Μαρκελλίνος; born , died 400), was a Greek and Roman soldier and historian who wrote the penultimate major historical account surviving from antiquit ...

(''Res Gestae'' 26.10.15–19) described the typical sequence of a tsunami, including an incipient earthquake, the sudden retreat of the sea and a following gigantic wave, after the 365 AD tsunami devastated

Alexandria Alexandria ( ; ) is the List of cities and towns in Egypt#Largest cities, second largest city in Egypt and the List of coastal settlements of the Mediterranean Sea, largest city on the Mediterranean coast. It lies at the western edge of the Nile ...

.Stanley, Jean-Daniel & Jorstad, Thomas F. (2005),
The 365 A.D. Tsunami Destruction of Alexandria, Egypt: Erosion, Deformation of Strata and Introduction of Allochthonous Material
" Tsunamis are an often underestimated hazard in the

Mediterranean Sea The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...

and parts of Europe. Of historical and current (with regard to risk assumptions) importance are the 1755 Lisbon earthquake and tsunami (which was caused by the Azores–Gibraltar transform fault), the

1783 Calabrian earthquakes The 1783 Calabrian earthquakes were a sequence of five strong earthquakes that hit the region of Calabria in southern Italy (then part of the Kingdom of Naples), the first two of which produced significant tsunamis. The epicenters form a clear ...

, each causing several tens of thousands of deaths and the

1908 Messina earthquake A devastating earthquake occurred on 28 December 1908 in Sicily and Calabria, southern Italy with a moment magnitude of 7.1 and a maximum Mercalli intensity of XI (''Extreme''). The epicentre was in the Strait of Messina which separates Sicily f ...

and tsunami. The tsunami claimed more than 123,000 lives in Sicily and Calabria and is among the deadliest natural disasters in modern Europe. The

Storegga Slide The three Storegga Slides () are amongst the largest known submarine landslides. They occurred at the edge of Norway's continental shelf in the Norwegian Sea, approximately 6225–6170 BCE. The collapse involved an estimated length of coastal s ...

in the Norwegian Sea and some examples of

tsunamis affecting the British Isles 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, ...

refer to landslide and

meteotsunami A meteotsunami or meteorological tsunamiTsunami Glossary 2008
, UNESCO is a

2004 Indian Ocean earthquake and tsunami On 26 December 2004, at 07:58:53 local time ( UTC+7), a major earthquake with a magnitude of 9.2–9.3 struck with an epicentre off the west coast of Aceh in northern Sumatra, Indonesia. The undersea megathrust earthquake, known in the sci ...

event mark it as the most devastating of its kind in modern times, killing around 230,000 people. The

Sumatra Sumatra () is one of the Sunda Islands of western Indonesia. It is the largest island that is fully within Indonesian territory, as well as the list of islands by area, sixth-largest island in the world at 482,286.55 km2 (182,812 mi. ...

n region is also accustomed to tsunamis, due to earthquakes of varying magnitudes that occur regularly off the coast of the island.

Causes

The principal generation mechanism of a tsunami is the displacement of a substantial volume of water or perturbation of the sea. This displacement of water is usually caused by earthquakes, but can also be attributed to landslides, volcanic eruptions, glacier calvings or more rarely by meteorites and nuclear tests. However, the possibility of a meteorite causing a tsunami is debated.

Seismicity

Tsunamis can be generated when the sea floor abruptly deforms and vertically displaces the overlying water. Tectonic earthquakes are a particular kind of earthquake that are associated with the Earth's crustal deformation; when these earthquakes occur beneath the sea, the water above the deformed area is displaced from its equilibrium position. More specifically, a tsunami can be generated when

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 associated with convergent or destructive

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 ...

move abruptly, resulting in water displacement, owing to the vertical component of movement involved. Movement on normal (extensional) faults can also cause displacement of the seabed, but only the largest of such events (typically related to flexure in the

outer trench swell The outer trench swell, outer trench high, or outer rise is a subtle ridge on the seafloor near an oceanic trench, where a descending plate begins to flex and fault in preparation for its descent into the mantle at a subduction zone. The lithosp ...

) cause enough displacement to give rise to a significant tsunami, such as the 1977 Sumba and 1933 Sanriku events. File:Eq-gen1.svg, Drawing of tectonic plate boundary before

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 ...

File:Eq-gen2.svg, Over-riding plate bulges under strain, causing

tectonic uplift Tectonic uplift is the orogeny, geologic uplift of Earth#Surface, Earth's surface that is attributed to plate tectonics. While Isostasy, isostatic response is important, an increase in the mean elevation of a region can only occur in response to ...

. File:Eq-gen3.svg, Plate slips, causing

subsidence Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope mov ...

and releasing energy into water. File:Eq-gen4.svg, The energy released produces tsunami waves. Tsunamis have a small wave height offshore, and a very long

(often hundreds of kilometres long, whereas normal ocean waves have a wavelength of only 30 or 40 metres), which is why they generally pass unnoticed at sea, forming only a slight swell usually about above the normal sea surface. They grow in height when they reach shallower water, in a

wave shoaling In fluid dynamics, wave shoaling is the effect by which ocean surface waves, surface waves, entering shallower water, change in wave height. It is caused by the fact that the group velocity, which is also the wave-energy transport velocity, decr ...

process described below. A tsunami can occur in any tidal state and even at low tide can still inundate coastal areas. On April 1, 1946, the 8.6 Aleutian Islands earthquake occurred with a maximum Mercalli intensity of VI (''Strong''). It generated a tsunami which inundated

Hilo Hilo () is the largest settlement in and the county seat of Hawaii County, Hawaiʻi, United States, which encompasses the Island of Hawaiʻi, and is a census-designated place (CDP). The population was 44,186 according to the 2020 census. I ...

on the island of Hawaii with a surge. Between 165 and 173 were killed. The area where the earthquake occurred is where the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...

floor is

subducting Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second pla ...

(or being pushed downwards) under Alaska. Examples of tsunamis originating at locations away from convergent boundaries include

Storegga The three Storegga Slides () are amongst the largest known submarine landslides. They occurred at the edge of Norway's continental shelf in the Norwegian Sea, approximately 6225–6170 BCE. The collapse involved an estimated length of coastal s ...

about 8,000 years ago,

Grand Banks The Grand Banks of Newfoundland are a series of underwater plateaus south-east of the island of Newfoundland on the North American continental shelf. The Grand Banks are one of the world's richest fishing grounds, supporting Atlantic cod, swordfi ...

in 1929, and

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 ...

in 1998 (Tappin, 2001). The Grand Banks and Papua New Guinea tsunamis came from earthquakes which destabilised sediments, causing them to flow into the ocean and generate a tsunami. They dissipated before travelling transoceanic distances. The cause of the Storegga sediment failure is unknown. Possibilities include an overloading of the sediments, an earthquake or a release of gas hydrates (methane etc.). The

1960 Valdivia earthquake The 1960 Valdivia earthquake and tsunami () or the Great Chilean earthquake (''Gran terremoto de Chile'') occurred on 22 May 1960. Most studies have placed it at 9.5–9.6 on the moment magnitude scale, while some studies have placed the magnitu ...

( ''M''_w 9.5),

1964 Alaska earthquake The 1964 Alaska earthquake, also known as the Great Alaska earthquake and Good Friday earthquake, occurred at 5:36 PM Alaska Standard Time, AKST on Good Friday, March 27, 1964.

(''M''_w 9.2),

2004 Indian Ocean earthquake On 26 December 2004, at 07:58:53 local time (UTC+07:00, UTC+7), a major earthquake with a magnitude of 9.2–9.3 struck with an epicenter, epicentre off the west coast of Aceh in northern Sumatra, Indonesia. The Submarine earthquake, undersea ...

(''M''_w 9.2), and

2011 Tōhoku earthquake Eleven or 11 may refer to: *11 (number) * One of the years 11 BC, AD 11, 1911, 2011 Literature * ''Eleven'' (novel), a 2006 novel by British author David Llewellyn *''Eleven'', a 1970 collection of short stories by Patricia Highsmith *''Eleven'' ...

(''M''_w9.0) are recent examples of powerful

megathrust earthquake Megathrust earthquakes occur at convergent plate boundaries, where one tectonic plate is forced underneath another. The earthquakes are caused by slip along the thrust fault that forms the contact between the two plates. These interplate earthq ...

s that generated tsunamis (known as teletsunamis) that can cross entire oceans. Smaller (''M''_w 4.2) earthquakes in Japan can trigger tsunamis (called local and regional tsunamis) that can devastate stretches of coastline, but can do so in only a few minutes at a time.

Landslides

The

Tauredunum event The Tauredunum event () of 563 AD was a tsunami on Lake Geneva (then under the Frankish territory of the Kingdom of Orleans), triggered by a massive landslide which caused widespread devastation and loss of life along the lakeshore. According to ...

was a large tsunami on

Lake Geneva Lake Geneva is a deep lake on the north side of the Alps, shared between Switzerland and France. It is one of the List of largest lakes of Europe, largest lakes in Western Europe and the largest on the course of the Rhône. Sixty percent () ...

in 563 CE, caused by sedimentary deposits destabilised by a landslide. In the 1950s, it was discovered that tsunamis larger than had previously been believed possible can be caused by giant

submarine landslides 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 ...

. These large volumes of rapidly displaced water transfer energy at a faster rate than the water can absorb. Their existence was confirmed in 1958, when a giant landslide in

Lituya Bay Lituya Bay (; Tlingit language, Tlingit: ''Ltu.aa'',. Spelled L'tua in translation of Tebenkov's log. meaning 'lake within the point') is a fjord located on the coast of the south-east part of the U.S. state of Alaska. It is long and wide at ...

, Alaska, caused the highest wave ever recorded, which had a height of . The wave did not travel far as it struck land almost immediately. The wave struck three boats—each with two people aboard—anchored in the bay. One boat rode out the wave, but the wave sank the other two, killing both people aboard one of them. Another landslide-tsunami event occurred in 1963 when a massive landslide from

Monte Toc Monte Toc, nicknamed The Walking Mountain by locals due to its tendency to experience landslides, is a mountain on the border between Veneto and Friuli-Venezia Giulia in Northern Italy. Its base is located next to the reservoir created by the Va ...

entered the reservoir behind the

Vajont Dam The Vajont Dam or Vaiont Dam is a disused hydro-electric dam in northern Italy. It is one of the tallest dams in the world, with a height of . It is in the valley of the Vajont (river) under Monte Toc, in the municipality of Erto e Casso, ...

in Italy. The resulting wave surged over the -high dam by and destroyed several towns. Around 2,000 people died. Scientists named these waves

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. Some geologists claim that large landslides from volcanic islands, 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 The Cumbre Vieja tsunami hazard refers to the risk that a volcanic eruption on the island of La Palma, Canary Islands, Spain, could cause a large volcanic landslide, landslide triggering a megatsunami in the Atlantic Ocean. Volcanic islands an ...

) 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 ...

, may be able to generate megatsunamis that can cross oceans, but this is disputed by many others. In general, landslides generate displacements mainly in the shallower parts of the coastline, and there is conjecture about the nature of large landslides that enter the water. This has been shown to subsequently affect water in enclosed bays and lakes, but a landslide large enough to cause a transoceanic tsunami has not occurred within recorded history. Susceptible locations are believed to be the Big Island of

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 ...

, Fogo in the

Cape Verde Islands Cape Verde or Cabo Verde, officially the Republic of Cabo Verde, is an island country and archipelagic state of West Africa in the central Atlantic Ocean, consisting of ten volcanic islands with a combined land area of about . These islands ...

, La Reunion in the

, and

on the island of

in the

; along with other volcanic ocean islands. This is because large masses of relatively unconsolidated volcanic material occurs on the flanks and in some cases detachment planes are believed to be developing. However, there is growing controversy about how dangerous these slopes actually are.

Volcanic eruptions

Other than by landslides or

sector collapse A sector collapse or lateral collapse is the structural failure and subsequent collapse of a minimum volume of of a volcano. Unlike smaller flank collapses, a sector collapse can involve the central volcanic pipe and historically this term had b ...

, volcanoes may be able to generate waves by

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 ...

submergence, caldera collapse, or underwater explosions. Tsunamis have been triggered by a number of volcanic eruptions. The best-known is perhaps the massive tsunami caused by the eruption of the

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 ...

volcano around 1600 BC, which is often mentioned as driving the destruction of many harbours in the region and ultimately the decline of Minoan civilization - a question still subject to open debate. Others include 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 ...

, and the 2022 Hunga Tonga–Hunga Ha'apai eruption. Over 20% of all fatalities caused by volcanism during the past 250 years are estimated to have been caused by volcanogenic tsunamis. Debate has persisted over the origins and source mechanisms of such tsunamis as those generated by Krakatoa in 1883, and they remain lesser understood than their seismic relatives. This poses the larger problem of awareness and preparedness, as exemplified by the eruption and collapse of Anak Krakatoa in 2018, which killed 426 and injured thousands when no warning was available. In all cases, developing better tsunami forecasting models and assessing the risks for densely populated coastal areas to be hit by severe tsunamis is a matter of global priority. It is still regarded that lateral landslides and ocean-entering pyroclastic currents are most likely to generate the largest and most hazardous waves from volcanism; however, field investigation of the Tongan event, as well as developments in numerical modelling methods, currently aim to expand the understanding of the other source mechanisms.

Meteorological

Some

meteorological Meteorology is the scientific study of the Earth's atmosphere and short-term atmospheric phenomena (i.e. weather), with a focus on weather forecasting. It has applications in the military, aviation, energy production, transport, agriculture ...

conditions, especially rapid changes in barometric pressure, as seen with the passing of a front, can displace bodies of water enough to cause trains of waves with wavelengths. These are comparable to seismic tsunamis, but usually with lower energies. Essentially, they are dynamically equivalent to seismic tsunamis, the only differences being 1) that meteotsunamis lack the transoceanic reach of significant seismic tsunamis, and 2) that the force that displaces the water is sustained over some length of time such that meteotsunamis cannot be modelled as having been caused instantaneously. In spite of their lower energies, on shorelines where they can be amplified by resonance, they are sometimes powerful enough to cause localised damage and potential for loss of life. They have been documented in many places, including the Great Lakes, the Aegean Sea, the English Channel, and the Balearic Islands, where they are common enough to have a local name, ''rissaga''. In Sicily they are called ''marubbio'' and in Nagasaki Bay, they are called ''abiki''. Some examples of destructive meteotsunamis include 31 March 1979 at Nagasaki and 15 June 2006 at Menorca, the latter causing damage in the tens of millions of euros. Meteotsunamis should not be confused with

storm surges A storm surge, storm flood, tidal surge, or storm tide is a coastal flood or tsunami-like phenomenon of rising water commonly associated with low-pressure weather systems, such as cyclones. It is measured as the rise in water level above the ...

, which are local increases in sea level associated with the low barometric pressure of passing tropical cyclones, nor should they be confused with setup, the temporary local raising of sea level caused by strong on-shore winds. Storm surges and setup are also dangerous causes of

coastal flooding Coastal flooding occurs when dry and low-lying land is submerged (flooded) by seawater. The range of a coastal Flood, flooding is a result of the elevation of floodwater that penetrates the inland which is controlled by the topography of the coas ...

in severe weather but their dynamics are completely unrelated to tsunami waves. They are unable to propagate beyond their sources, as waves do.

Human-made or triggered tsunamis

The accidental

Halifax Explosion On the morning of 6 December 1917, the French cargo ship collided with the Norwegian vessel in the harbour of Halifax, Nova Scotia, Canada. ''Mont-Blanc'', laden with Explosive material, high explosives, caught fire and exploded, devastat ...

in 1917 triggered an high tsunami in the harbour at

Halifax, Nova Scotia Halifax is the capital and most populous municipality of the Provinces and territories of Canada, Canadian province of Nova Scotia, and the most populous municipality in Atlantic Canada. As of 2024, it is estimated that the population of the H ...

, Canada. There have been studies of the potential for the use of explosives to induce tsunamis as a tectonic weapon. As early as

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

(1939–1945), consideration of the use of conventional explosives was explored, and New Zealand's military forces initiated

Project Seal The tsunami bomb was an attempt during World War II to develop a tectonic weapon that could create destructive tsunamis. The project commenced after United States Navy officer E.A. Gibson noticed small waves generated by explosions used to clea ...

, which attempted to create small tsunamis with explosives in the area of what is now

Shakespear Regional Park Shakespear Regional Park () is a nature park in the Auckland Region of New Zealand. It is located at the tip of the Whangaparāoa Peninsula, and is named after the Shakespear family who first came on to the land when Sir Robert Hamilton purchase ...

at the tip of the

Whangaparāoa Peninsula The Whangaparāoa Peninsula is a suburban area about 30–50 km north of Auckland, New Zealand. It had residents in It stretches from Red Beach, New Zealand, Red Beach, where it connects to Kingsway, Orewa and Silverdale, and exte ...

in the

Auckland Region Auckland () is one of the 16 regions of New Zealand, which takes its name from the eponymous urban areas of New Zealand, urban area. The region encompasses the Auckland, Auckland metropolitan area, smaller towns, rural areas, and the islands o ...

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

; the attempt failed. There has been considerable speculation about the possibility of using

nuclear weapon A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission or atomic bomb) or a combination of fission and fusion reactions (thermonuclear weapon), producing a nuclear exp ...

s to cause tsunamis near an enemy coastline. Nuclear testing in the Pacific Proving Ground by the United States generated poor results. In

Operation Crossroads Operation Crossroads was a pair of nuclear weapon tests conducted by the United States at Bikini Atoll in mid-1946. They were the first nuclear weapon tests since Trinity on July 16, 1945, and the first detonations of nuclear devices sinc ...

in July 1946, two bombs were detonated, one in the air over and one underwater within the shallow waters of the deep

lagoon A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') an ...

Bikini Atoll Bikini Atoll ( or ; Marshallese language, Marshallese: , , ), known as Eschscholtz Atoll between the 19th century and 1946, is a coral reef in the Marshall Islands consisting of 23 islands surrounding a central lagoon. The atoll is at the no ...

. The bombs detonated about from the nearest island, where the waves were no higher than when they reached the shoreline. Other underwater tests, mainly

Operation Hardtack I Operation Hardtack I was a series of 35 nuclear tests conducted by the United States from April 28 to August 18 in 1958 at the Pacific Proving Grounds. At the time of testing, the Operation Hardtack I test series included more nuclear detonation ...

/Wahoo in deep water and Operation Hardtack I/Umbrella in shallow water, confirmed the results. Analysis of the effects of

shallow Shallow may refer to: Places * Shallow (underwater relief), where the depth of the water is low compared to its surroundings * Shallow Bay (disambiguation), various places * Shallow Brook, New Jersey, United States * Shallow Inlet, Victoria ...

and

deep Deep or The Deep may refer to: Places United States * Deep Creek (Appomattox River tributary), Virginia * Deep Creek (Great Salt Lake), Idaho and Utah * Deep Creek (Mahantango Creek tributary), Pennsylvania * Deep Creek (Mojave River tributary ...

underwater explosions indicate that the energy of the explosions does not easily generate the kind of deep, all-ocean waveforms typical of tsunamis because most of the energy creates

steam Steam is water vapor, often mixed with air or an aerosol of liquid water droplets. This may occur due to evaporation or due to boiling, where heat is applied until water reaches the enthalpy of vaporization. Saturated or superheated steam is inv ...

, causes vertical fountains above the water, and creates compressional waveforms. Tsunamis are hallmarked by permanent large vertical displacements of very large volumes of water which do not occur in explosions.

Characteristics

Tsunamis are caused by earthquakes, landslides, volcanic explosions, glacier calvings, and

bolide A bolide is normally taken to mean an exceptionally bright meteor, but the term is subject to more than one definition, according to context. It may refer to any large Impact crater, crater-forming body, or to one that explodes in the atmosphere. ...

s. They cause damage by two mechanisms: the smashing force of a wall of water travelling at high speed, and the destructive power of a large volume of water draining off the land and carrying a large amount of debris with it, even with waves that do not appear to be large. While everyday

wind wave In fluid dynamics, a wind wave, or wind-generated water wave, is a surface wave that occurs on the free surface of bodies of water as a result of the wind blowing over the water's surface. The contact distance in the direction of the wind is ...

s have a

(from crest to crest) of about and a height of roughly , a tsunami in the deep ocean has a much larger wavelength of up to . Such a wave travels at well over , but owing to the enormous wavelength the wave oscillation at any given point takes 20 or 30 minutes to complete a cycle and has an amplitude of only about . This makes tsunamis difficult to detect over deep water, where ships are unable to feel their passage. The velocity of a tsunami can be calculated by obtaining the square root of the depth of the water in metres multiplied by the acceleration due to gravity (approximated to 10 m/s²). For example, if the Pacific Ocean is considered to have a depth of 5000 metres, the velocity of a tsunami would be = ≈ , which equates to a speed of about . This is the formula used for calculating the velocity of shallow-water waves. Even the deep ocean is shallow in this sense because a tsunami wave is so long (horizontally from crest to crest) by comparison. The reason for the Japanese name "harbour wave" is that sometimes a village's

fishermen A fisherman or fisher is someone who captures fish and other animals from a body of water, or gathers shellfish. Worldwide, there are about 38 million commercial and subsistence fishers and fish farmers. Fishermen may be professional or recr ...

would sail out, and encounter no unusual waves while out at sea fishing, and come back to land to find their village devastated by a huge wave. As the tsunami approaches the coast and the waters become shallow,

compresses the wave and its speed decreases below . Its wavelength diminishes to less than and its amplitude grows enormously—in accord with

Green's law In fluid dynamics, Green's law, named for 19th-century British mathematician George Green (mathematician), George Green, is a conservation law describing the evolution of breaking wave, non-breaking, surface gravity waves Wave propagation, propa ...

. Since the wave still has the same very long

, the tsunami may take minutes to reach full height. Except for the very largest tsunamis, the approaching wave does not

break Break or Breaks or The Break may refer to: Time off from duties * Recess (break), time in which a group of people is temporarily dismissed from its duties * Break (work), time off during a shift/recess ** Coffee break, a short mid-morning rest ...

, but rather appears like a fast-moving

. Open bays and coastlines adjacent to very deep water may shape the tsunami further into a step-like wave with a steep-breaking front. When the tsunami's wave peak reaches the shore, the resulting temporary rise in sea level is termed ''run up''. Run up is measured in metres above a reference sea level. A large tsunami may feature multiple waves arriving over a period of hours, with significant time between the wave crests. The first wave to reach the shore may not have the highest run-up. About 80% of tsunamis occur in the Pacific Ocean, but they are possible wherever there are large bodies of water, including lakes. However, tsunami interactions with shorelines and the seafloor topography are extremely complex, which leaves some countries more vulnerable than others. For example, the Pacific coasts of the United States and Mexico lie adjacent to each other, but the United States has recorded ten tsunamis in the region since 1788, while Mexico has recorded twenty-five since 1732. Similarly, Japan has had more than a hundred tsunamis in recorded history, while the neighbouring island of Taiwan has registered only two, in 1781 and 1867.

Drawback

All

wave In physics, mathematics, engineering, and related fields, a wave is a propagating dynamic disturbance (change from List of types of equilibrium, equilibrium) of one or more quantities. ''Periodic waves'' oscillate repeatedly about an equilibrium ...

s have a positive and negative peak; that is, a ridge and a trough. In the case of a propagating wave like a tsunami, either may be the first to arrive. If the first part to arrive at the shore is the ridge, a massive breaking wave or sudden flooding will be the first effect noticed on land. However, if the first part to arrive is a trough, a drawback will occur as the shoreline recedes dramatically, exposing normally submerged areas. The drawback can exceed hundreds of metres, and people unaware of the danger sometimes remain near the shore to satisfy their curiosity or to collect fish from the exposed seabed. A typical wave period for a damaging tsunami is about twelve minutes. Thus, the sea recedes in the drawback phase, with areas well below sea level exposed after three minutes. For the next six minutes, the wave trough builds into a ridge which may flood the coast, and destruction ensues. During the next six minutes, the wave changes from a ridge to a trough, and the flood waters recede in a second drawback. Victims and debris may be swept into the ocean. The process repeats with succeeding waves.

Scales of intensity and magnitude

As with earthquakes, several attempts have been made to set up scales of tsunami intensity or magnitude to allow comparison between different events.

Intensity scales

The first scales used routinely to measure the intensity of tsunamis were the '' Sieberg- Ambraseys scale'' (1962), used in the

and the ''Imamura-Iida intensity scale'' (1963), used in the Pacific Ocean. The latter scale was modified by Soloviev (1972), who calculated the tsunami intensity "''I''" according to the formula: :

\mathit = \frac + \log_ \mathit_

where

\mathit_

is the "tsunami height" in metres, averaged along the nearest coastline, with the tsunami height defined as the rise of the water level above the normal tidal level at the time of occurrence of the tsunami. This scale, known as the ''Soloviev-Imamura tsunami intensity scale'', is used in the global tsunami catalogues compiled by the NGDC/NOAA and the Novosibirsk Tsunami Laboratory as the main parameter for the size of the tsunami. This formula yields: * ''I'' = 2 for

\mathit_

= 2.8 metres * ''I'' = 3 for

\mathit_

= 5.5 metres * ''I'' = 4 for

\mathit_

= 11 metres * ''I'' = 5 for

\mathit_

= 22.5 metres * etc. In 2013, following the intensively studied tsunamis in 2004 and 2011, a new 12-point scale was proposed, the Integrated Tsunami Intensity Scale (ITIS-2012), intended to match as closely as possible to the modified ESI2007 and

EMS Ems or EMS may refer to: Places and rivers * Domat/Ems, a Swiss municipality in the canton of Grisons * Ems (river) (Eems), a river in northwestern Germany and northeastern Netherlands that discharges in the Dollart Bay * Ems (Eder), a river o ...

earthquake intensity scales.

Magnitude scales

The first scale that genuinely calculated a magnitude for a tsunami, rather than an intensity at a particular location was the ML scale proposed by Murty & Loomis based on the potential energy. Difficulties in calculating the potential energy of the tsunami mean that this scale is rarely used. Abe introduced the ''tsunami magnitude scale

\mathit_

'', calculated from, :

\mathit_ =  \log h +  \log R + \mathit

where ''h'' is the maximum tsunami-wave amplitude (in m) measured by a tide gauge at a distance ''R'' from the epicentre, ''a'', ''b'' and ''D'' are constants used to make the M_t scale match as closely as possible with the moment magnitude scale.

Tsunami heights

Several terms are used to describe the different characteristics of tsunami in terms of their height: * Amplitude, Wave Height, or Tsunami Height: Refers to the height of a tsunami relative to the normal sea level at the time of the tsunami, which may be tidal High Water, or Low Water. It is different from the crest-to-trough height which is commonly used to measure other type of wave height. * Run-up Height, or Inundation Height: The height reached by a tsunami on the ground above sea level, Maximum run-up height refers to the maximum height reached by water above sea level, which is sometimes reported as the maximum height reached by a tsunami. * Flow Depth: Refers to the height of tsunami above ground, regardless of the height of the location or sea level. * (Maximum) Water Level: Maximum height above sea level as seen from trace or water mark. Different from maximum run-up height in the sense that they are not necessarily water marks at inundation line/limit.

Warnings and predictions

Drawbacks can serve as a brief warning. People who observe drawback (many survivors report an accompanying sucking sound) can survive only if they immediately run for high ground or seek the upper floors of nearby buildings. In 2004, ten-year-old

Tilly Smith Tilly Smith (born 1994) is a British woman who, as a child, was credited with saving the lives of approximately 100 beachgoers at Mai Khao Beach in Thailand by warning them minutes before the arrival of the tsunami caused by the 2004 Indian Ocea ...

Surrey Surrey () is a Ceremonial counties of England, ceremonial county in South East England. It is bordered by Greater London to the northeast, Kent to the east, East Sussex, East and West Sussex to the south, and Hampshire and Berkshire to the wes ...

, England, was on Maikhao beach in

Phuket Phuket (; , , or ''Tongkah'') is one of the Southern Thailand, southern Provinces of Thailand, provinces (''changwat'') of Thailand. It consists of the island of Phuket, List of islands of Thailand, the country's largest island, and another 3 ...

, Thailand with her parents and sister, and having learned about tsunamis recently in school, told her family that a tsunami might be imminent. Her parents warned others minutes before the wave arrived, saving dozens of lives. She credited her geography teacher, Andrew Kearney. In the

drawback was not reported on the African coast or any other east-facing coasts that it reached. This was because the initial wave moved downwards on the eastern side of the

megathrust Megathrust earthquakes occur at convergent plate boundaries, where one tectonic plate is forced underneath another. The earthquakes are caused by slip along the thrust fault that forms the contact between the two plates. These interplate earthqu ...

and upwards on the western side. The western pulse hit coastal Africa and other western areas. A tsunami cannot be precisely predicted, even if the magnitude and location of an earthquake is known.

Geologist A geologist is a scientist who studies the structure, composition, and History of Earth, history of Earth. Geologists incorporate techniques from physics, chemistry, biology, mathematics, and geography to perform research in the Field research, ...

oceanographer Oceanography (), also known as oceanology, sea science, ocean science, and marine science, is the scientific study of the ocean, including its physics, chemistry, biology, and geology. It is an Earth science, which covers a wide range of top ...

s, and

seismologist Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes (or generally, quakes) and the generation and propagation of elastic ...

s analyse each earthquake and based on many factors may or may not issue a tsunami warning. However, there are some warning signs of an impending tsunami, and automated systems can provide warnings immediately after an earthquake in time to save lives. One of the most successful systems uses bottom pressure sensors, attached to buoys, which constantly monitor the pressure of the overlying water column. Regions with a high tsunami risk typically use

tsunami warning system A tsunami warning system (TWS) is used to detect tsunamis in advance and issue the warnings to prevent loss of life and damage to property. It is made up of two equally important components: a network of sensors to detect tsunamis and a communic ...

s to warn the population before the wave reaches land. On the west coast of the United States, which is prone to tsunamis from the Pacific Ocean, warning signs indicate evacuation routes. In Japan, the populace is well-educated about earthquakes and tsunamis, and along Japanese shorelines, tsunami warning signs remind people of the natural hazards along with a network of warning sirens, typically at the top of the cliffs of surrounding hills. The Pacific Tsunami Warning System is based in

Honolulu Honolulu ( ; ) is the List of capitals in the United States, capital and most populous city of the U.S. state of Hawaii, located in the Pacific Ocean. It is the county seat of the Consolidated city-county, consolidated City and County of Honol ...

. It monitors Pacific Ocean seismic activity. A sufficiently large earthquake magnitude and other information triggers a tsunami warning. While the subduction zones around the Pacific are seismically active, not all earthquakes generate a tsunami. Computers assist in analysing the tsunami risk of every earthquake that occurs in the Pacific Ocean and the adjoining land masses. File:Bamfield Tsunami Hazard Zone sign.jpg, Tsunami hazard sign at

Bamfield Bamfield is a community that is surrounded by Crown Land, First Nation Lands belonging to the Huu-ay-aht Nations, and portions of the Pacific Rim National Park, located on Barkley Sound, Vancouver Island in British Columbia, Canada. The commu ...

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 ...

File: A tsunami warning sign in Kamakura, Japan.jpg, A tsunami warning sign in

Kamakura , officially , is a city of Kanagawa Prefecture in Japan. It is located in the Kanto region on the island of Honshu. The city has an estimated population of 172,929 (1 September 2020) and a population density of 4,359 people per km2 over the tota ...

, Japan File:Zona de Inundabilidad.jpg, A Tsunami hazard sign (Spanish – English) in

Iquique Iquique () is a port List of cities in Chile, city and Communes of Chile, commune in northern Chile, capital of both the Iquique Province and Tarapacá Region. It lies on the Pacific coast, west of the Pampa del Tamarugal, which is part of the At ...

, Chile File:Tsunami Evacuation Route signage south of Aberdeen Washington.jpg, alt=Photo of evacuation sign, Tsunami Evacuation Route signage along

U.S. Route 101 U.S. Route 101, or U.S. Highway 101 (US 101), is a major north–south highway that traverses the states of California, Oregon, and Washington on the West Coast of the United States. It is part of the United States Numbered Highway Syst ...

, in

Washington Washington most commonly refers to: * George Washington (1732–1799), the first president of the United States * Washington (state), a state in the Pacific Northwest of the United States * Washington, D.C., the capital of the United States ** A ...

As a direct result of the Indian Ocean tsunami, a re-appraisal of the tsunami threat for all coastal areas is being undertaken by national governments and the United Nations Disaster Mitigation Committee. A tsunami warning system is being installed in the Indian Ocean. Dart tsunamicover

Computer model Computer simulation is the running of a mathematical model on a computer, the model being designed to represent the behaviour of, or the outcome of, a real-world or physical system. The reliability of some mathematical models can be determin ...

s can predict tsunami arrival, usually within minutes of the arrival time. Bottom pressure sensors can relay information in real time. Based on these pressure readings and other seismic information and the seafloor's shape (

bathymetry Bathymetry (; ) is the study of underwater depth of ocean floors ('' seabed topography''), river floors, or lake floors. In other words, bathymetry is the underwater equivalent to hypsometry or topography. The first recorded evidence of wate ...

) and coastal

topography Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the landforms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary sci ...

, the models estimate the amplitude and surge height of the approaching tsunami. All

Pacific Rim The Pacific Rim comprises the lands around the rim of the Pacific Ocean. The '' Pacific Basin'' includes the Pacific Rim and the islands in the Pacific Ocean. The Pacific Rim roughly overlaps with the geological Pacific Ring of Fire. List ...

countries collaborate in the Tsunami Warning System and most regularly practise evacuation and other procedures. In Japan, such preparation is mandatory for government, local authorities, emergency services and the population. Along the United States west coast, in addition to sirens, warnings are sent on television and radio via the

National Weather Service The National Weather Service (NWS) is an Government agency, agency of the Federal government of the United States, United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weathe ...

, using the

Emergency Alert System The Emergency Alert System (EAS) is a Emergency population warning, national warning system in the United States designed to allow authorized officials to broadcast emergency alerts and warning messages to the public via Cable television, cable ...

Possible animal reaction

Some zoologists hypothesise that some animal species have an ability to sense subsonic

Rayleigh wave Rayleigh waves are a type of surface acoustic wave that travel along the surface of solids. They can be produced in materials in many ways, such as by a localized impact or by Piezoelectricity, piezo-electric Interdigital transducer, transduction, ...

s from an earthquake or a tsunami. If correct, monitoring their behaviour could provide advance warning of earthquakes and tsunamis. However, the evidence is controversial and is not widely accepted. There are unsubstantiated claims about the Lisbon quake that some animals escaped to higher ground, while many other animals in the same areas drowned. The phenomenon was also noted by media sources in

Sri Lanka Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka, also known historically as Ceylon, is an island country in South Asia. It lies in the Indian Ocean, southwest of the Bay of Bengal, separated from the Indian subcontinent, ...

in the

. It is possible that certain animals (e.g.,

elephant Elephants are the largest living land animals. Three living species are currently recognised: the African bush elephant ('' Loxodonta africana''), the African forest elephant (''L. cyclotis''), and the Asian elephant ('' Elephas maximus ...

s) may have heard the sounds of the tsunami as it approached the coast. The elephants' reaction was to move away from the approaching noise. By contrast, some humans went to the shore to investigate and many drowned as a result.

Mitigation

In some tsunami-prone countries, earthquake engineering measures have been taken to reduce the damage caused onshore. Japan, where tsunami science and response measures first began following a disaster in 1896, has produced ever-more elaborate countermeasures and response plans. The country has built many tsunami walls of up to high to protect populated coastal areas. Other localities have built

floodgate Floodgates, also called stop gates, are adjustable gates used to control water flow in flood barriers, reservoir, river, stream, or levee systems. They may be designed to set spillway crest heights in dams, to adjust flow rates in sluices and ...

s of up to high and channels to redirect the water from an incoming tsunami. However, their effectiveness has been questioned, as tsunamis often overtop the barriers. The

Fukushima Daiichi nuclear disaster The Fukushima nuclear accident was a major nuclear accident at the Fukushima Daiichi Nuclear Power Plant in Ōkuma, Fukushima, Japan, which began on 11 March 2011. The cause of the accident was the 2011 Tōhoku earthquake and tsunami, which r ...

was directly triggered by the

2011 Tōhoku earthquake and tsunami On 11 March 2011, at 14:46:24 Japan Standard Time, JST (05:46:24 UTC), a 9.0–9.1 Submarine earthquake, undersea megathrust earthquake occurred in the Pacific Ocean, east of the Oshika Peninsula of the Tōhoku region. It lasted approx ...

, when waves exceeded the height of the plant's sea wall and flooded the emergency generators.Phillip Lipscy, Kenji Kushida, and Trevor Incerti. 2013.
The Fukushima Disaster and Japan’s Nuclear Plant Vulnerability in Comparative Perspective
". ''Environmental Science and Technology'' 47 (May), 6082–6088.

Iwate Prefecture is a Prefectures of Japan, prefecture of Japan located in the Tōhoku region of Honshu. It is the second-largest Japanese prefecture (behind Hokkaido) at , with a population of 1,165,886 (as of July 1, 2023). Iwate Prefecture borders Aomori Pre ...

, which is an area at high risk from tsunami, had tsunami barriers walls ( Taro sea wall) totalling long at coastal towns. The 2011 tsunami toppled more than 50% of the walls and caused catastrophic damage. The Okushiri, Hokkaidō tsunami, which struck within two to five minutes of the earthquake on July 12, 1993, created waves tall—as high as a 10-storey building. The port town of Aonae was completely surrounded by a tsunami wall, but the waves washed right over the wall and destroyed all the wood-framed structures in the area. The wall may have succeeded in slowing down and moderating the height of the tsunami, but it did not prevent major destruction and loss of life.

Footnotes

References

IOC Tsunami Glossary
by the

Intergovernmental Oceanographic Commission The Intergovernmental Oceanographic Commission of UNESCO (IOC/UNESCO) was established by resolution 2.31 adopted by the General Conference of the United Nations Educational, Scientific and Cultural Organization (UNESCO). It first met in Paris at ...

(IOC) at th
International Tsunami Information Centre
(ITIC) of

UNESCO The United Nations Educational, Scientific and Cultural Organization (UNESCO ) is a List of specialized agencies of the United Nations, specialized agency of the United Nations (UN) with the aim of promoting world peace and International secur ...

Tsunami Terminology
at

NOAA The National Oceanic and Atmospheric Administration (NOAA ) is an American scientific and regulatory agency charged with forecasting weather, monitoring oceanic and atmospheric conditions, charting the seas, conducting deep-sea exploratio ...

* In June 2011, the VOA

Special English Learning English (previously known as Special English) is a controlled version of the English language first used on October 19, 1959, and still presented daily by the United States broadcasting service Voice of America (VOA). World news and oth ...

service of the

Voice of America Voice of America (VOA or VoA) is an international broadcasting network funded by the federal government of the United States that by law has editorial independence from the government. It is the largest and oldest of the American internation ...

broadcast a 15-minute programme on tsunamis as part of its weekly Science in the News series. The programme included an interview with an NOAA official who oversees the agency's tsunami warning system. A transcript and MP3 of the programme, intended for English learners, can be found a
The Ever-Present Threat of Tsunamis.

abelard.org.
''tsunamis: tsunamis travel fast but not at infinite speed''. retrieved March 29, 2005. * Dudley, Walter C. & Lee, Min (1988: 1st edition) ''Tsunami!''

* Iwan, W.D., ''editor'', 2006, Summary report of the Great Sumatra Earthquakes and Indian Ocean tsunamis of December 26, 2004 and March 28, 2005: Earthquake Engineering Research Institute, EERI Publication #2006-06, 11 chapters, 100-page summary, plus CD-ROM with complete text and supplementary photographs, EERI Report 2006–06.
website
* Kenneally, Christine (December 30, 2004). "Surviving the Tsunami." ''Slate''
website
* Lambourne, Helen (March 27, 2005). "Tsunami: Anatomy of a disaster."

BBC News BBC News is an operational business division of the British Broadcasting Corporation (BBC) responsible for the gathering and broadcasting of news and current affairs in the UK and around the world. The department is the world's largest broad ...

website
* Macey, Richard (January 1, 2005). "The Big Bang that Triggered A Tragedy," ''

The Sydney Morning Herald ''The Sydney Morning Herald'' (''SMH'') is a daily Tabloid (newspaper format), tabloid newspaper published in Sydney, Australia, and owned by Nine Entertainment. Founded in 1831 as the ''Sydney Herald'', the ''Herald'' is the oldest continuous ...

'', p 11—quoting Dr Mark Leonard, seismologist at Geoscience Australia.
Interactive Map of Historical Tsunamis
from NOAA National Centers for Environmental Information * Tappin, D; 2001. Local tsunamis. Geoscientist. 11–8, 4–7.

'' Telegraph.co.uk''
Philippines warned to prepare for Japan's tsunami
''Noypi.ph''

External links

; Reporting Centers
Tsunami alert
page (in English) from

Japan Meteorological Agency The Japan Meteorological Agency (JMA; ''気象庁, Kishō-chō'') is a division of the Ministry of Land, Infrastructure, Transport and Tourism dedicated to the Scientific, scientific observation and research of natural phenomena. Headquartered ...

NOAA Centre
–

National Oceanic and Atmospheric Administration The National Oceanic and Atmospheric Administration (NOAA ) is an American scientific and regulatory agency charged with Weather forecasting, forecasting weather, monitoring oceanic and atmospheric conditions, Hydrography, charting the seas, ...

Caribbean Tsunami Information Centre
(CTIC)

– Pacific Marine Environmental Laboratory ; History & Research
IOC Tsunami Glossary
– International Tsunami Information Center (

)
Tsunami Data and Information
–

National Centers for Environmental Information The National Centers for Environmental Information (NCEI) is a U.S. government agency that manages one of the world's largest archives of atmospheric, coastal, geophysical, and oceanic data. The current director is Deke Arndt. NCEI is operate ...

World's Tallest Tsunami
– geology.com
Tsunami & Earthquake Research at the USGS
–

United States Geological Survey The United States Geological Survey (USGS), founded as the Geological Survey, is an agency of the U.S. Department of the Interior whose work spans the disciplines of biology, geography, geology, and hydrology. The agency was founded on Mar ...

Intergovernmental Oceanographic Commission
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Terminology

Tsunami

Tidal wave

Seismic sea wave

Other terms

History

Causes

Seismicity

Landslides

Volcanic eruptions

Meteorological

Human-made or triggered tsunamis

Characteristics

Drawback

Scales of intensity and magnitude

Intensity scales

Magnitude scales

Tsunami heights

Warnings and predictions

Possible animal reaction

Mitigation

See also

Footnotes

References

Further reading

External links