Tsunami: on boxing day 2004, nature reminded us of its awesome power.
The world's land masses sit on top of plates that float on the molten core of our planet. These plates move and where they meet up with one another earthquakes and volcanoes are common.
About 160 kilometres off the west coast of the Indonesian island of Sumatra, the Indian plate The India or Indian Plate is a minor tectonic plate. It was originally a part of the ancient continent of Gondwanaland from which it split off, eventually becoming a major plate. About 50 to 55 million years ago, it fused with the adjacent Indo-Australian Plate. meets the Burma plate The Burma Plate is a small tectonic plate or microplate located in Southeast Asia, often considered a part of the larger Eurasian Plate. The Andaman Islands, Nicobar Islands, and northwestern Sumatra are located on the plate. . The two plates rub together along a zone that is 1,200 kilometres long and 480 kilometres wide.
The Indian plate is sliding under the Burma plate. But, the movement is jerky jerky
see biltong. , as the submerging plate tends to drag the upper plate down with it. As pressure builds, the upper plate breaks free, springing back to its original position. That's what happened on 26 December 2004.
The amount of energy released was vast. (One estimate puts it at 30 percent greater than all the energy used in the United States United States, officially United States of America, republic (2005 est. pop. 295,734,000), 3,539,227 sq mi (9,166,598 sq km), North America. The United States is the world's third largest country in population and the fourth largest country in area. in a year.) It was enough to cause Earth to wobble wobble /wob·ble/ (wob´'l) to move unsteadily or unsurely back and forth or from side to side. See under hypothesis.
1. on its axis by about 2.5 centimetres and to speed up its rotation by a few tiny fractions of a second. The plate on which Sumatra sits lurched back about 15 metres in a few seconds. At the same time, the seabed lifted displacing a vast quantity of ocean water.
Dr. Roger Musson, is an earthquake expert with the British Geological Survey The British Geological Survey (BGS) is a partly publicly-funded body which aims to advance geoscientific knowledge of the United Kingdom landmass and its continental shelf by means of systematic surveying, monitoring and research. in Edinburgh, Scotland. He told The Times newspaper: "The effect of the earthquake is like throwing a stone in a pond, except that you are throwing it from below. You get the equivalent of a splash and water is displaced with waves spreading outwards."
The Japanese, who have a lot of experience with earthquake generated waves, call them "tsunamis" (tsu = harbour + nami = wave). The word was coined by fishers who returned to port to find their homes devastated dev·as·tate
tr.v. dev·as·tat·ed, dev·as·tat·ing, dev·as·tates
1. To lay waste; destroy.
2. To overwhelm; confound; stun: was devastated by the rude remark. , although they hadn't been aware of any wave in the open water.
Out in the ocean a tsunami is often barely noticeable; it may cause the ocean surface to rise by only a few centimetres but it can travel at the speed of a jet aircraft. Despite their apparent insignifance, tsumanis contain phenominal amounts of energy.
Tad Murty Tad S. Murty(Or Murthy) is an Indian-Canadian oceanographer and expert on tsunamis. He is the former president of the Tsunami Society. He is an adjunct professor in the departments of Civil Engineering and Earth Sciences of the Tsunami Society has estimated the Boxing Day "seismic sea waves," as the oceanographers call them, to have contained the energy equivalent of about five megatons of TNT TNT: see trinitrotoluene.
in full trinitrotoluene
Pale yellow, solid organic compound made by adding nitrate (−NO2) groups to toluene. . That's more than twice the explosive energy used during the whole of World War II, including the atomic bombs dropped on Hiroshima and Nagasaki. He also estimated that tsunamis represent only a quarter of the energy of the initial earthquake.
Eventually, a tsunami approaches land. As the ocean floor rises towards the coast, the forward speed of the wave drops but the water begins to pile up. When the tsunami crashes ashore the effect is catastrophic. No wonder the most frequently heard description of the destruction caused by the recent tsunami was "Unimaginable."
THE BIG ONE
Scientists say there are several geological time-bombs Scattered across the world's oceans; one of them is in the volcanic Canary Islands. A huge piece (estimated to weigh 500 billion tones) of the western flank of the island of La Palma is in danger of falling into the Atlantic Ocean. This may happen at any time during the next few thousand years triggering a mega-tsunami. The wave, measuring several hundred metres in height, would reach the eastern seaboard of the American continent in a few hours.