We have threads about volcanoes, earthquakes, the weather, etc. but I could not find one dedicated to tsunamis. Tsunamis are secondary events that can happen for a variety of reasons, like earthquakes, volcanic eruptions, the detonation of very powerful explosive devices, earth slides, large icebergs breaking off, or meteorite impacts. Because they are secondary events, tsunamis will often be mentioned in connection with their primary causative event. Tsunamis are still important, especially the major ones that leave their marks in the pages of history. Below are few descriptions, images, and some history about tsunamis.
How a tsunami moves
The International Tsunami Information Center writes:
Map of wave heights generated by the tsunami on December 26, 2004
Below is an example of how the tsunami wave varies with location. It is not clear to me if it is feet or meter, but comparing with the description on the Wiki it would seem to be in feet. For instance, up to 9 meter waves were reported on the coasts of Somalia. Nine meters would be close to 30 feet and deserving of a red color. Notice that the wave in some direction appears to maintain more energy, and that the coast of Western Australia had waves one would not expect when just looking at the ocean in between.
Map of the travel time for the wave generated by the tsunami on December 26, 2004
The color and lines signify time and areas by hours. South Africa is about 5000 km away. Somalia 3000 km.
An example of a well described historical tsunami
While earthquakes can destroy by breaking everything apart, tsunamis can destroy by washing away. This is well described, also, by ancient sources. About the effect of the Crete earthquake in 365 there is, (even if neither the date, nor the event in the Wiki is 100 % established, the Wiki mentions 350-450!):
Clearly, some areas are more exposed. In the picture below, the triangle signifies an earthquake as the cause, the square a landslide, and the question mark an unknown source. A white sign means no fatalities, the orange and violet some, while yellow is from 101-1000 and the red is more than a 1000.
The explanation below the image mentions a distinction between local, regional and teletsunamis
The last list to include from the above page shows:
A recent example from Greenland
In the left list, the last event was caused by a landslide on Greenland in 2017. Earlier this year, a Youtube surfaced from the village: Uncut and Unseen: Greenland Tsunami (First Wave to Largest Wave in 6 mins.). The village is an image from an ice age, nothing tropical whatsoever, but one clearly sees the different stages of water moving in and out:
The Wiki has about this even:
The page about Tsunami Events divides them into categories.
Mostly a tsunami is a minor issue, but occasionally it can be very serious, as the example from December 26, 2004 showed, but also the March 11, 2011, event in Japan, which destroyed the nuclear power plant at Fukushima. For this reason, it is good to be cautious and know the signs.
How a tsunami moves
The International Tsunami Information Center writes:
Tsunamis create waves and the waves move. Below are two maps that depict the models for the effects on the ocean in terms of the height of a tsunami wave, and how the wave travels.From the area where the tsunami originates, waves travel outward in all directions. Once the wave approaches the shore, it builds in height. The topography of the coastline and the ocean floor will influence the size of the wave. There may be more than one wave and the succeeding one may be larger than the one before. That is why a small tsunami at one beach can be a giant wave a few miles away.[...]
Earthquake-induced movement of the ocean floor most often generates tsunamis. If a major earthquake or landslide occurs close to shore, the first wave in a series could reach the beach in a few minutes, even before a warning is issued. Areas are at greater risk if they are less than 25 feet above sea level and within a mile of the shoreline. Drowning is the most common cause of death associated with a tsunami. Tsunami waves and the receding water are very destructive to structures in the run-up zone. Other hazards include flooding, contamination of drinking water, and fires from gas lines or ruptured tanks.
Map of wave heights generated by the tsunami on December 26, 2004
Below is an example of how the tsunami wave varies with location. It is not clear to me if it is feet or meter, but comparing with the description on the Wiki it would seem to be in feet. For instance, up to 9 meter waves were reported on the coasts of Somalia. Nine meters would be close to 30 feet and deserving of a red color. Notice that the wave in some direction appears to maintain more energy, and that the coast of Western Australia had waves one would not expect when just looking at the ocean in between.
Map of the travel time for the wave generated by the tsunami on December 26, 2004
The color and lines signify time and areas by hours. South Africa is about 5000 km away. Somalia 3000 km.
An example of a well described historical tsunami
While earthquakes can destroy by breaking everything apart, tsunamis can destroy by washing away. This is well described, also, by ancient sources. About the effect of the Crete earthquake in 365 there is, (even if neither the date, nor the event in the Wiki is 100 % established, the Wiki mentions 350-450!):
The International Tsunami Information Center has a map of 1200 historical tsunamis.The Roman historian Ammianus Marcellinus described in detail the tsunami that hit Alexandria and other places in the early hours of 21 July 365.[3] His account is particularly noteworthy for clearly distinguishing the three main phases of a tsunami, namely an initial earthquake, the sudden retreat of the sea and an ensuing gigantic wave rolling inland:
The tsunami in 365 was so devastating that the anniversary of the disaster was still commemorated annually at the end of the sixth century in Alexandria as a "day of horror".[19][10]Slightly after daybreak, and heralded by a thick succession of fiercely shaken thunderbolts, the solidity of the whole earth was made to shake and shudder, and the sea was driven away, its waves were rolled back, and it disappeared, so that the abyss of the depths was uncovered and many-shaped varieties of sea-creatures were seen stuck in the slime; the great wastes of those valleys and mountains, which the very creation had dismissed beneath the vast whirlpools, at that moment, as it was given to be believed, looked up at the sun's rays. Many ships, then, were stranded as if on dry land, and people wandered at will about the paltry remains of the waters to collect fish and the like in their hands; then the roaring sea as if insulted by its repulse rises back in turn, and through the teeming shoals dashed itself violently on islands and extensive tracts of the mainland, and flattened innumerable buildings in towns or wherever they were found. Thus in the raging conflict of the elements, the face of the earth was changed to reveal wondrous sights. For the mass of waters returning when least expected killed many thousands by drowning, and with the tides whipped up to a height as they rushed back, some ships, after the anger of the watery element had grown old, were seen to have sunk, and the bodies of people killed in shipwrecks lay there, faces up or down. Other huge ships, thrust out by the mad blasts, perched on the roofs of houses, as happened at Alexandria, and others were hurled nearly two miles from the shore, like the Laconian vessel near the town of Methone which I saw when I passed by, yawning apart from long decay.[18]
Clearly, some areas are more exposed. In the picture below, the triangle signifies an earthquake as the cause, the square a landslide, and the question mark an unknown source. A white sign means no fatalities, the orange and violet some, while yellow is from 101-1000 and the red is more than a 1000.
The explanation below the image mentions a distinction between local, regional and teletsunamis
The estimated death toll from listed historical tsunamisNOAA’s National Centers for Environmental Information (NCEI) and co-located World Data Service (WDS) for Geophysics and the International Tsunami Information Center (ITIC), a UNESCO/IOC-NOAA partnership, have collaborated to produce a map showing tsunami sources. The information comes from the NCEI Global Historical Tsunami Database that includes information on tsunami source events throughout the world that range in date from 1610 B.C. to A.D. 2017. The tsunami definitions are from the Tsunami Glossary 2016 published by UNESCO IOC.
Of the 2,500 events in the NCEI Global Historical Tsunami Database, over 1,200 confirmed tsunami source events are displayed on the map. A total of 252 confirmed deadly tsunamis have resulted in over 540,000 known (or confirmed) deaths. The death total may include deaths from the generating event (e.g., earthquake) as it is not always possible to separate deaths from the different causes. These figures should be much higher, but in many events the actual number of fatalities is not known. The reporting of deadly tsunamis is not homogeneous in space or time, particularly for periods prior to the 1900s.
Tsunamis are also classified by how far away the effects of the waves were observed. For example, the effects of a local tsunami are confined to coasts within about 100 km (62 miles) or less than 1 hour tsunami travel time from its source. A tsunami capable of destruction within 1,000 km (621 miles) or 1-3 hours travel time from its source is considered a regional tsunami. Most destructive tsunamis can be classified as local or regional. It follows that many tsunami-related deaths and considerable property damage result from these tsunamis (Table 1). In fact, 90% of all tsunami deaths in the historic record occurred in the local or regional area within the first 3 hours of the event. Between 1980 and 2017 there were 34 local or regional confirmed tsunamis that resulted in deaths and property damage (Table 2); 24 of these were in the Pacific and its adjacent seas.
A distant or teletsunami is a tsunami originating from a far away source, generally more than 1,000 km (621 miles) or more than 3 hours tsunami travel time away. They usually start as a local tsunami that causes extensive destruction near the source; the waves then continue to travel across the entire ocean basin with sufficient energy to cause additional deaths and destruction on distant shores. In the last 300 years, there have been at least 43 confirmed damaging teletsunamis and 18 caused deaths more than 1,000 km (621 miles) from the source (Table 3).
The last list to include from the above page shows:
A recent example from Greenland
In the left list, the last event was caused by a landslide on Greenland in 2017. Earlier this year, a Youtube surfaced from the village: Uncut and Unseen: Greenland Tsunami (First Wave to Largest Wave in 6 mins.). The village is an image from an ice age, nothing tropical whatsoever, but one clearly sees the different stages of water moving in and out:
The Wiki has about this even:
Records of tsunamisOn 17 June 2017, a landslide measuring 300 m × 1,100 m (980 ft × 3,610 ft) fell about 1 km (3,300 ft) into the Karrak fiord, causing a tsunami that hit Nuugaatsiaq.[2][3] Four people were killed, nine injured and eleven buildings were washed into the water.[2][3][4][5] In the beginning the tsunami had a height of 90 m (300 ft), but it was significantly lower once it hit the settlement.[3] Initially it was unclear if the landslide was caused by a small earthquake (magnitude 4),[2][5] but later it was confirmed that the landslide had caused the tremors.[3]
The page about Tsunami Events divides them into categories.
Looking at Tsunamis 2020-2021, I found
The list from 2021 contains earthquakes mainly and the associated parameters like their epicenter, their size, and if they led to a tsunami warning, and then how high they were. It is not clear to me how they mark tsunamis not caused by earthquakes, perhaps somebody knows?
Mostly a tsunami is a minor issue, but occasionally it can be very serious, as the example from December 26, 2004 showed, but also the March 11, 2011, event in Japan, which destroyed the nuclear power plant at Fukushima. For this reason, it is good to be cautious and know the signs.