Tsunami
A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, generally an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater explosions (including detonations of underwater nuclear devices), landslides, glacier calvings, meteorite impacts and other disturbances above or below water all have the potential to generate a tsunami.
Tsunami waves do not resemble normal sea waves, because their wavelength is far longer. Rather than appearing as a breaking wave, a tsunami may instead initially resemble a rapidly rising tide, and for this reason they are often referred to as tidal waves. Tsunamis generally consist of a series of waves with periods ranging from minutes to hours, arriving in a so-called "wave train". 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.
Causes of Tsunami
Tsunami are huge ocean waves caused by natural forces like underwater earthquakes. Tsunami are caused when the forces of these phenomena rapidly displace large amounts of water.
Most tsunami occur when there is an earthquake or volcanic eruption in the sea or ocean. This is caused when there are plate boundaries that are meeting in plate tectonics processes. This will cause shock waves to be radiated out of the epicenter. This natural event will cause a rise or fall of the seabed. This will create a wave deep in the ocean (or less frequently in other large body of water).
Tsunami can also be caused by landslides, such as a cliff-side of a mountain near shore that falls into a large body of water or ocean.
Powerful bombs, like nuclear bombs, are tested, dropped, or detonated in the sea or ocean and can cause shock waves to be radiated out that move the ocean waters in waves as described above.
The also occur when large asteroids fall into the water. This is extremely rare, and the asteroids must be very large to cause a large water displacement to form a tsunami wave. But they are known to have occurred. Meteorites will not cause high waves as they are usually much smaller than asteroids by the time they have been burned in the atmosphere on the way to the surface.
How Earthquakes Cause Tsunamis
The illustration below shows a subduction earthquake (one where a denser plates shifts below its neighboring plate, at left). Energy is transferred and the displaced water forms a wave. As the wave travels and enters shallower water in the coastal area, it begins to increase in amplitude
Tsunamis are not always colossal waves when they come into the shore. In fact, "... most tsunamis do not result in giant breaking waves (like normal surf waves at the beach that curl over as they approach shore). Rather, they come in much like very strong and very fast tides (i.e., a rapid, local rise in sea level). Nevertheless, there is destruction of life and of property by floating debris and impact of water. The tsunami produces a series of rushing waves and also a series of withdrawals.
If you think about throwing a rock in water, a ripple is formed. It is the same principle involving a meteor or an earthquake, except they form bigger ripples. If you think about that ripple, it seems to disappear as time goes on--but in actuality, it does not stop. In the picture below we can see that a tsunami is very fast (the speed often compared with that of a jet) and it has a height of 20 inches.
However, we need to take into consideration the effect of the tsunami reaching the shore. The speed is diminished but the wave height is increased drastically.
How Volcanoes Cause Tsunamis
There are two different ways that volcanoes can cause seismic waves. One possibility is for a land-based volcano to break down and collapse, forcing large amounts of ash and debris into the water. This sudden change and displacement of the water column transfers to kinetic energy and results in waves. More debris can create a bigger increase in wave amplitude and number.
Tsunamis can also be induced by submarine volcanoes. These underwater volcanoes can collapse downwards or spew forth lava heating the surrounding water quickly.
Undersea landslides and land sliding into the sea
Undersea landslides and land sliding into the sea may cause localised tsunami. Undersea landslides occur when a large amount of sediment is dislodged from the seafloor, displacing a water column and potentially generating tsunami. Land sliding into the sea, usually caused by an earthquake, may also cause destructive local tsunami.
Distribution of Tsunami
An average of 85% of all tsunamis have been observed in the Pacific Ocean in the "Ring of Fire. the distribution of tsunamis in the world's oceans and seas:
History of Tsunami
As early as 426 BC the Greek historian Thucydides inquired in his book History of the Peloponnesian War about the causes of tsunami, and was the first to argue that ocean earthquakes must be the cause.
The cause, 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.The Roman historian Ammianus Marcellinus (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.
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A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, generally an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater explosions (including detonations of underwater nuclear devices), landslides, glacier calvings, meteorite impacts and other disturbances above or below water all have the potential to generate a tsunami.
Tsunami waves do not resemble normal sea waves, because their wavelength is far longer. Rather than appearing as a breaking wave, a tsunami may instead initially resemble a rapidly rising tide, and for this reason they are often referred to as tidal waves. Tsunamis generally consist of a series of waves with periods ranging from minutes to hours, arriving in a so-called "wave train". 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.
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| Furious Ocean |
Causes of Tsunami
Tsunami are huge ocean waves caused by natural forces like underwater earthquakes. Tsunami are caused when the forces of these phenomena rapidly displace large amounts of water.
Most tsunami occur when there is an earthquake or volcanic eruption in the sea or ocean. This is caused when there are plate boundaries that are meeting in plate tectonics processes. This will cause shock waves to be radiated out of the epicenter. This natural event will cause a rise or fall of the seabed. This will create a wave deep in the ocean (or less frequently in other large body of water).
Tsunami can also be caused by landslides, such as a cliff-side of a mountain near shore that falls into a large body of water or ocean.
Powerful bombs, like nuclear bombs, are tested, dropped, or detonated in the sea or ocean and can cause shock waves to be radiated out that move the ocean waters in waves as described above.
The also occur when large asteroids fall into the water. This is extremely rare, and the asteroids must be very large to cause a large water displacement to form a tsunami wave. But they are known to have occurred. Meteorites will not cause high waves as they are usually much smaller than asteroids by the time they have been burned in the atmosphere on the way to the surface.
How Earthquakes Cause Tsunamis
The illustration below shows a subduction earthquake (one where a denser plates shifts below its neighboring plate, at left). Energy is transferred and the displaced water forms a wave. As the wave travels and enters shallower water in the coastal area, it begins to increase in amplitude
Tsunamis are not always colossal waves when they come into the shore. In fact, "... most tsunamis do not result in giant breaking waves (like normal surf waves at the beach that curl over as they approach shore). Rather, they come in much like very strong and very fast tides (i.e., a rapid, local rise in sea level). Nevertheless, there is destruction of life and of property by floating debris and impact of water. The tsunami produces a series of rushing waves and also a series of withdrawals.
If you think about throwing a rock in water, a ripple is formed. It is the same principle involving a meteor or an earthquake, except they form bigger ripples. If you think about that ripple, it seems to disappear as time goes on--but in actuality, it does not stop. In the picture below we can see that a tsunami is very fast (the speed often compared with that of a jet) and it has a height of 20 inches.
However, we need to take into consideration the effect of the tsunami reaching the shore. The speed is diminished but the wave height is increased drastically.
How Volcanoes Cause Tsunamis
There are two different ways that volcanoes can cause seismic waves. One possibility is for a land-based volcano to break down and collapse, forcing large amounts of ash and debris into the water. This sudden change and displacement of the water column transfers to kinetic energy and results in waves. More debris can create a bigger increase in wave amplitude and number.
Tsunamis can also be induced by submarine volcanoes. These underwater volcanoes can collapse downwards or spew forth lava heating the surrounding water quickly.
Undersea landslides and land sliding into the sea
Undersea landslides and land sliding into the sea may cause localised tsunami. Undersea landslides occur when a large amount of sediment is dislodged from the seafloor, displacing a water column and potentially generating tsunami. Land sliding into the sea, usually caused by an earthquake, may also cause destructive local tsunami.
 |
| A landslide into Lituya Bay, Alaska, in 1958 caused a localised tsunami. The bare areas around the lake side in this image indicate where the trees were stripped away by the tsunami. |
An average of 85% of all tsunamis have been observed in the Pacific Ocean in the "Ring of Fire. the distribution of tsunamis in the world's oceans and seas:
History of Tsunami
As early as 426 BC the Greek historian Thucydides inquired in his book History of the Peloponnesian War about the causes of tsunami, and was the first to argue that ocean earthquakes must be the cause.
The cause, 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.The Roman historian Ammianus Marcellinus (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.
Related Videos
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