The largest earthquake in 40 years shifted huge geological plates beneath the Indian Ocean on Dec. 26, 2004, causing a immense and abrupt displacement of millions of tons of water. Indonesia villages closest to the epicenter were swamped within minutes, while elsewhere the waves radiated outward, making landfall at speeds topping 500 mph (www.cbsnews.com). The phenomenon we call tsunami is a series of large waves of extremely long wavelength and period usually generated by a violent, impulsive undersea disturbance or activity near the coast or in the ocean. When a sudden displacement of a large volume of water occurs, or if the sea floor is suddenly raised or dropped by an earthquake, big tsunami waves can be formed by forces of gravity. The waves travel out of the area of origin and can be extremely unsafe and destructive when they reach the shore. Often the term, "seismic or tidal sea wave" is used to describe the same phenomenon; however the terms are misleading, because tsunami waves can be generated by other, non seismic disturbances such as volcanic eruptions or underwater landslides, and have physical characteristics different of tidal waves. The tsunami waves are completely unrelated to the astronomical tides - which are caused by the extraterrestrial, gravitational influences of the moon, sun, and the planets. Thus, the Japanese word "tsunami", meaning "harbor wave" is the correct, official and all-inclusive term. It has been internationally adopted because it covers all forms of impulsive wave generation. By far, the most destructive tsunamis are generated from large, shallow earthquakes with an epicenter or fault line near or on the ocean floor. These usually occur in regions of the earth characterized by tectonic subduction along tectonic plate boundaries. The high seismicity of such regions is caused by the collision of tectonic plates. When these plates move past each other, they cause large earthquakes, which tilt, offset, or displace large areas of the ocean floor from a few kilometers to as much as a 1,000 km or more. The abrupt vertical displacements over such large areas, disturb the ocean's surface, displace water, and generate destructive tsunami waves. The waves can travel great distances from the source region, spreading destruction along their path. It should be noted that not all earthquakes generate tsunamis. Usually, it takes an earthquake with a Richter magnitude exceeding 7.5 to produce a destructive tsunami (www.prh.noaa.gov).
People search for family through destroyed houses at Sirombu village in Nias, North Sumatra, Indonesia, Dec. 29, 2004.
Not only was Indonesia hit dramatically by this disaster, other areas included: Somalia where approximately 300 were said to be killed, Maldives where the death toll was 82, the tsunami left 37 of the Maldives's roughly 200 inhabited islands temporarily unsuitable for human habitation, destroying drinking water and food supplies as well as communications and power generation equipment, a government spokesman said. National elections scheduled for Dec. 31 were postponed indefinitely. Officials say the Maldives escaped a worse fate because the tsunami didn't gain height and break over the low-lying islands in the same way as it did over the coasts of large Asian countries, and because of Maldivians' experience in surviving in the water. However, because the Maldives is so low - by some estimates it's the world's lowest-lying country - a huge percentage of the country was underwater, and more than one third of the population was receiving some form of emergency aid after the disaster. Sri Lanka was also hit with a death toll of between 31,000 and 38,000, 40% of whom were children. In India, at least 10,700 were killed, in Bangladesh at least 2 were killed, in Myanmar an estimated 90 people lost their lives, in Thailand more than 5300 were killed, with about 2900 others missing. In Indonesia the death...
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