This cartoon shows schematically how a subduction earthquake generates a tsunami. The green material is the lithosphere (which is brittle) and the purple-red material is the asthenosphere (which, while still solid, is deformable). The lithosphere is divided into the overriding (continental) plate on the right and the downgoing (oceanic) plate on the left. The overriding plate is locked against the downgoing plate, so as the downgoing plate subducts, the overriding plate is progressively deformed. The front edge of the overriding plate is flexed downwards while the coastline is lifted. After a few hundred years, so much strain energy has been stored in the system (think of a spring that is wound up too tight) that something has to give. The result is an earthquake. The earthquake relieves the accumulated strain in just a matter of minutes, during which the overriding plate relaxes back to its original unstrained condition. The toe of the overriding plate kicks up and the shoreline drops.
High School - College
When a major undersea earthquake occurs near the coast, a destructive tsunami can result that will hit near-by coasts in minutes and also travel across entire oceans causing damage 1000’s of kilometers away and up to 24 hours later. To alert far-away coasts, internationally coordinated tsunami early warning systems, such as the Pacific Tsunami Warning and Mitigation System (PTWS), have been established to quickly provide tsunami threat information to countries.
These images were generated from the ETOPO2v2 (2006) database. ETOPO2v2 was created at NGDC from digital databases of seafloor and land elevations on a 2-minute latitude/longitude grid (1 minute of latitude = 1 nautical mile, or 1.852 km). Assumed illumination is from the west; shading is computed as a function of the east-west slope of the surface with a nonlinear exaggeration favoring low-relief areas. A Cylindrical Equidistant projection was used for the world image, which spans 360 degrees of of longitude from 180 West eastward to 180 East; latitude coverage is from 90 degrees North to 90 degrees South. The resolution of the gridded data varies from true 2-minute for the Atlantic, Pacific, and Indian Ocean floors and all land masses to 5 minutes for the Arctic Ocean floor. Clicking on a square above brings up a 512 x 512 pixel color relief image of the 45 degree area selected, clicking on the 512 x 512 image brings up the full-resolution 1350 x 1350 pixel (roughly 3 mb) color image of the area.
Not too long ago, scientists studying the ocean made a fascinating discovery that has helped us better understand our planet Earth. Down in the deep and dark waters, they found hot springs on the ocean floor releasing warm and mineral-rich fluids – these are called hydrothermal vents.
Scientists believe that 80 percent of the volcanic eruptions on Earth take place in the ocean. Most of these volcanoes are thousands of feet deep, and difficult to find. But in May of 2009, scientists captured the deepest ocean eruption ever found.