You tsunamis are giant waves that form in the oceans as a result of earthquakes, and other factors associated with tectonism, as well as external causes, such as falling meteorites. These waves travel at high speed and are between 100 km and 500 km in length. À As they approach the coast, they lose speed and gain height, which is from 30 m to 40 m. Tsunamis have a high potential for destruction, as observed in Indonesia in 2004 and Japan in 2011.
Read too: What is the difference between hurricane, tornado and cyclone?
What is a tsunami?
Tsunami, a word of Japanese origin that means “port wave” (tsu = port; nami = wave), is a giant wave that forms in the oceanthrough in big ones water disturbances, that can have diverse origins, from tectonic movements in the ocean floor to the impact of a meteorite. the tsunamis has high destructive potential and can have devastating consequences for the affected areas.
Causes of a Tsunami
the tsunamis graduate through of disturbances caused nothe oceans (or at the bottom of the oceans), which release large amounts of energy, causing the displacement of large volumes of water. These events can be associated with geological factors in the area or exogenous factors, such as the fall of meteorites.
The tectonic order phenomena are the main causes of the giant waves characteristic of tsunamis, mainly earthquakes originating in the ocean floor. Its occurrence is more common in areas of tectonic instability, where different plates meet, which characterizes a fault zone.
O volcanism it is also another triggering factor for tsunamis, although it occurs less frequently. The volcanic activity in this case can occur both in the ocean floor and in coastal areas, such as the destruction of the volcanic caldera during process of eruption and the consequent sliding of large amounts of debris into the sea, or even the flow of lava and others materials.
Landslides (or avalanches) that happen at depth, in the steepest areas of the ocean floor, can also cause the propagation of energy for the formation of tsunamis. Other events that bring large volumes of material into the ocean and displace huge amounts of water likewise have the potential to generate tidal waves.
Characteristics of a Tsunami
the tsunamis have wavelengths ranging from 100 km 500 km, while the common waves reach a few hundred meters. Its amplitude (measurement of the wave above standing water, which corresponds to the equilibrium position) is small and variable in the meter scale.
Another important feature of tsunamis is their high speed on open sea. In these areas, waves travel at up to 890 km/h. As they approach the coast, that is, they advance over shallower areas, the tsunamis lose speed and gain altitude, reaching from 30 m to 40 m. There are, however, records of waves that reached 50 meters in height.
This phenomenon has very high destructive power, since the waves break violently when they reach the coast and its waters manage to advance hundreds of kilometers over the affected areas.
Read too: What is a cyclone?
10 worst tsunamis in history
The Circle of Fire, in Opacific ocean, is the region of the planet most susceptible to the occurrence of tsunamis, since it is the area of greatest tectonic instability on Earth. However, the phenomenon is not restricted to this area only. Discover the 10 worst tsunamis ever recorded.
Sumatra (Indonesia), 2004: caused by a earthquake of magnitude 9.1, which generated waves 50 meters high. A total of 230,000 people lost their lives.
Fukushima (Japan), 2011: generated by the worst earthquake in the history of Japan, of magnitude 9.1. The waves that hit the Japanese coast reached 10 meters in height. Some sources mention waves of up to 15 meters. Among its consequences are the Fukushima nuclear accident and 18,000 victims between dead and missing.
Lisbon (Portugal), 1755: caused by a earthquake that generated waves of 30 meters. About 60,000 people died in the country and also in Spain and Morocco.
Krakatoa (Indonesia), 1883: caused by the explosion of the volcanic caldera of Anak Krakatoa, forming waves of 37 meters. Considering the eruption and the violent action of the waters, 40 thousand people died.
Enshunada Sea (Japan), 1498: generated by an earthquake, claimed a total of 31,000 victims.
Nankaido (Japan), 1707: generated by an earthquake, waves of 25 meters followed. The number of victims was 30,000.
Sanriku (Japan), 1896: formed by an earthquake, the waves reached 38 meters. A total of 22,000 people were victims in Japan, and another 4,000 on the east coast of China.
Arica, 1868: at the time the province belonged to the Peru, but today it is part of Chilean territory. The tsunami, with waves of 21 meters, was caused by earthquakes. It claimed 21,000 victims and reverberated through other countries, such as the Australia.
Ryukyu Islands (Japan), 1771: generated by an earthquake and killed about 12,000 people. The waves exceeded 10 meters.
Ise Bay (Japan), 1586: earthquake followed by waves of six meters. He claimed eight thousand victims.
![The worst tsunami in history happened in Indonesia in December 2004. [1]](/f/e8ea532d250e6c0f15f8c874c9d575dc.jpg)
Differences between Tsunami and Tsunami
Youtsunamisare earthquakes that occur on the ocean floor, generating the anomalous movement of water and may give rise to large waves, which propagate through the ocean. Depending on the amount of energy released, waves can reach gigantic proportions and move at very high speeds in the open sea, which characterizes tsunamis. Tsunamis are therefore one of the possible consequences of tsunamis.
solved exercises
Question 1 - (UECE) Tsunamis or great ocean tides are due to:
A) small oceanic depth in the places where they originate, causing the sudden displacement of oceanic waters to the continental slope.
B) earthquakes in which the epicenter is located in distant continental areas.
C) earthquakes in oceanic areas, causing the waves to move towards the coast, where there is less depth, and increasing the friction between the waters and the seabed.
D) continental volcanic eruptions, whose displacement of magmatic material is oriented towards the coast.
Resolution
Alternative C. Seismic shocks on the ocean floor are the most common causes of tsunamis.
Question 2 - The tsunamis that hit Indonesia's Sumatra island in 2004 and the east coast of Japan seven years later are the two most destructive on record. Together, they add up to nearly 250,000 victims and damage that exceeds hundreds of billions of dollars.
Regarding the tsunami phenomenon, it is correct to state:
A) They occur exclusively in the Circle of Fire, as it is an area of great tectonic instability.
B) They are characterized by wavelengths that can reach 500 km.
C) Waves move at high speeds, which increase as they approach the coast.
D) Tsunamis are only caused by earthquakes and volcanic activity on the ocean floor.
E) Tsunamis and tidal waves are terms that describe the same phenomena.
Resolution
Alternative B. Tsunamis are characterized by long waves ranging between 100 km and 500 km. This differentiates them from common waves, whose length is on the order of meters.
Image credit
[1] Frans Delian / Shutterstock
By Paloma Guitarrara
Geography teacher
