Which plates cause tsunamis

As the water moves up and down, seeking to regain its balance, a tsunami is born. Not all earthquakes cause tsunamis. Key earthquake characteristics that contribute to tsunami generation are location, magnitude size , and depth. Most tsunamis are generated by earthquakes with magnitudes over 7.

Generally, an earthquake must exceed magnitude 8. The amount of movement of the ocean floor, the size of the area over which an earthquake occurs, and the depth of the water above the earthquake are also important factors in the size of a resulting tsunami. In addition to the previously highlighted tsunamis and , other examples of earthquake-generated tsunamis include:. To learn more about earthquakes, visit the U.

Geological Survey's Earthquake Hazards Program. Please Contact Us. Toggle navigation JetStream. Tsunami Generation: Earthquakes View enlarged image of earth's tectonic plates. Source: U. Geological Survey. View enlarged image of earth's tectonic plates. When an overriding plate breaks free and rises seaward the seafloor rises and lifts the water above it creating an earthquake along the subduction zone.

A tsunami is generated. As the bulge end of the plate collapses it thins out and lowers coastal areas. The tsunami races off in two different directions, one,growing in size towards landfall nearby, the other to a distant shore.

Toggle navigation. Get earthquake and tsunami alerts. Signup now FREE. If you like this content, help us spread awareness If you like this content, like us on Facebook : or follow us on Twitter! Subduction zone related earthquakes are particularly effective in generating tsunamis.

Although most tsunamis are caused by underwater earthquakes, it is to be noted however that not all underwater earthquakes cause tsunamis: usually, an earthquake has to be over about magnitude 7. Picture this: You have a bathtub full of water and a hard-backed book.

If you dip the book into the bathwater spine-first and move the book back and forth longways, what do you observe? Not much, except you've ruined your book. Now if you hold the book with its flat side on the surface of the water and move the book up and down in the water, you should generate some big waves as the vertical motion you've imposed on the water column is transferred to horizontal motion as the wave travels away from the source.

This is basically how a tsunami is generated. Do we expect California to "fall into the ocean" as in the cartoon I drew? Think about why or why not based on the material you just read. Volcanic eruptions can also produce tsunamis. The rules are similar to the rules for earthquakes. In order for a volcano to produce a tsunami you need:. An eruption that sends a large enough volume of material into the water to displace a significant volume of water.

If a large eruption sends a great volume of material into the water, it creates the vertical disturbance necessary to make a tsunami. This is one of the reasons the Cumbre Vieja volcano is worrisome: either an eruption or a landslide from a flank collapse could produce a tsunami.

Want to learn more about volcanoes and tsunamis? One of the earliest modern records of a devastating tsunami comes from the eruption of Krakatoa in August Skip to main content.