Speech About Plate Tectonics

Science Speech

The concept of plate tectonics was formulated in the 1960s by a German scientist called Alfred Wegener who had a theory that all the continents fit together like a puzzle. According to the theory, Earth has a rigid outer layer, known as the lithosphere, which is about 100 km or 60 miles thick and overlies a layer called the asthenosphere. The lithosphere is broken up into seven very large continentals- and ocean-sized plates, six or seven medium-sized regional plates, and several small ones. These plates move relative to each other, typically at rates of 5 to 10 cm per year, and interact along their boundaries, where they converge, diverge and Transform. these interactions are thought to be responsible for most of Earth’s seismic

Only a few of the rivers are navigable. Relatively little of Japan's land mass is suitable for agriculture. The population and areas of agriculture are therefore concentrated together. Japan's islands are very beautiful and varied, but they can be treacherous. Because japan is on top the subduction zone of the boundary of four tectonic plates: the Pacific, North American, Eurasian and Filipino plates Earthquakes are common and result from a fault that circles the Pacific Ocean, causing earthquakes on the west coast of North and South America as well. They are frequent in Japan, occurring more often than they are felt. Even so, one big enough to be noticed occurs every three days in Tôkyô. Occasionally they do serious damage. Tidal waves occasionally result from undersea earthquakes, and typhoons sometimes hit Japan as they move north from the South Pacific.

Therefore, mountains of Japan contain 10 per-cent of the world's most active volcanoes. Japan is riddled with faults and is located at the junction of four tectonic plates. In the last 75 years, the Japanese archipelago or areas immediately offshore have experienced five earthquakes measuring more than eight on the Richter scale; and 17 measuring more than seven on the Richter scale. It is unusual for a year to go by without three or four earthquakes measuring 6.0 or more. Japan accounts for about 20 percent of the earthquakes of magnitude 6 or greater on the Richter scale. Each day about 1,000 tremors that can be felt are produced in Japan. More than 130,000 quakes were logged in Japan in 2005. Each year nearly ten percent of the energy released in the world in earthquakes is centered around Japan. In the last century Japan has experienced 25 destructive earthquakes. In some places small earthquakes are felt on a weekly and even daily basis. Japanese seismic scale is slightly different from the Richter scale used in the United States and elsewhere in the world.