Tsunamis are formed by a displacement of water - a landslide, earthquake, volcanic eruption, or slippage of the boundary between two of the earth's tectonic plates - slabs of rock 50 to 650 feet (15 to 200 meters) thick that carry the Earth's continents and seas on an underground ocean of much hotter, semi-solid material.
Tsunamis can travel over 500 mph (800 k/ph) at the deepest point of the water, but slow as they near the shore, eventually hitting the shore at 20 to 30 (32 to 48 k/ph). The energy of the wave's speed is transferred to height and sheer force as it nears shore.
Major or Notable Tsunamis: November 1, 1755 - An estimated 60,000 people are killed when an earthquake strikes Lisbon, Portugal, and causes a tsunami.
August 27, 1883 - An estimated 36,000 people are killed when the Krakatau volcano erupts causing a tsunami in the Indonesian islands of Java and Sumatra.
June 15, 1896 - An estimated 28,000 people are killed when an 8.5 magnitude earthquake strikes Sanriku, Japan, causing a tsunami.
December 28, 1908 - An estimated 70,000-100,000 people are killed when a 7.2 magnitude earthquake strikes Messina, Italy, and causes a tsunami in the Straights of Messina.
May 22, 1960 - An estimated 1,500 people are killed when a magnitude 9.5 earthquake strikes Chile and causes a tsunami.
March 28, 1964 - An estimated 128 people are killed when a magnitude 9.2 earthquake strikes Prince William Sound, Alaska, and causes a tsunami.
August 16, 1976 - An estimated 4,000-8,000 people are killed when a magnitude earthquake 8.0 strikes the Philippines and causes a tsunami.
July 17, 1998 - An estimated 2,200 people are killed when a magnitude 7.0 earthquake strikes Papua New Guinea and causes a tsunami.
December 26, 2004 - An estimated 227,898 people are killed when a 9.1 magnitude earthquake strikes near Sumatra, Indonesia, and causes a subsequent tsunami in 14 countries in South Asia and East Africa.
October 25, 2010 - An estimated 449 people are killed when a magnitude 7.7 earthquake strikes Indonesia and causes a tsunami.
March 11, 2011 - A 9.1 magnitude earthquake takes place 231 miles northeast of Tokyo. The earthquake causes a tsunami with 30 ft waves that damage several nuclear reactors in the area. The combined total of confirmed deaths and missing is more than 22,000 (nearly 20,000 deaths and 2,500 missing). (Source: Japan's Fire and Disaster Management Agency)
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