Tsunamis and Their Causes
Tsunamis and Their Causes : A tsunami is a series of ocean waves generated by the sudden displacement of large volumes of water by thrust-type submarine earthquakes, submarine volcanic eruptions, slumps or coastal landslides. Underwater earthquakes are the most frequent cause of tsunamis, but not all major coastal or near-coastal earthquakes produce tsunamis. At present there is no method to determine if a tsunami has been generated by an earthquake except to note the magnitude and location of the epicentre, and then detect the arrival of characteristic tsunami waves at a network of tidal stations and buoys in the open ocean that respond by a satellite link. On December 26, 2004, a magnitude 9.1 earthquake, the fourth largest earthquake in the world since 1900 (and the largest since 1964), generated a tsunami that crossed into the Pacific and Atlantic Oceans. It was recorded in New Zealand and along the west and east coasts of South and North America and caused more casualties than any other tsunami in recorded history. In total, more than 283,000 people were killed, thousands were listed as missing, and more than 1,127,000 were displaced by the earthquake and tsunami in ten countries in South Asia and East Africa. Here on the west coast of North America, tsunamis are usually categorized as local, regional or Pacific-wide, depending on the size of the area affected
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