By Joe Espiritu
In the past weeks an earthquake of great magnitude hit Haiti a Caribbean country. Then later, another tremor just as devastating hit Chile, a South American country facing the Pacific. Recently some shocks had been felt in Taiwan and the Philippines. Somehow, those quakes are not related to one another as some religious adherents want to depict. They are just a part of geological activities that is continuously occurring since the formation of the earth.
The earth began as a mass of stellar matter blown away from the sun. For several billion years it cooled and solidified into a planet 8,000 miles in diameter. Today, the very center of the earth a core of iron and nickel 4,400 miles in diameter has a temperature of 5,400 degrees Fahrenheit, slightly cooler than the sun. It is surrounded by a mantle of molten rock nearly 1,800 miles thick.
The crust, which floats around the mantle, is proportionately thinner than an eggshell. Under the ocean, it is some five miles thick and elsewhere is around thirty miles. Though we think that the surface or crust is relatively stable, the forces in the mantle stretch wrinkles, shoves around or breaks through the crust. And this causes earthquakes. Crust disturbances are classified into tectonic or volcanic.
When liquid rock forces up the mantle through one or more fissures in the crust, volcanism occurs. Thus tremors accompany volcanic explosions. If the crusts shift because of some disturbance in the mantle, then the tremor is tectonic. The latter is most devastating. Mt Pinatubo erupted but fortunately the eruption only covered the surroundings with lahar. No lives were reported lost.
The crust maybe disturbed several ways. It may crack open if they are of the same level or a slippage may occur if they are of different levels. The crust layers may be forced together. One layer my slip over the other or they may be forced upwards forming mountains. In the past tectonic activity threw up mountains such as the Himalayas and the Andes. It also formed the deep sea trenches like the Mariana and Puerto Rico deep.
Subterranean activities are frequent where the crust is weak. If the disturbance is under the sea, the waters will be roiled to form great waves. When a huge chunk of earth fell down a deep sea abyss off Alaska, a tsunami swept Hawaii causing much damage to property and lives lost. When a layer of the continental shelf slipped over the other off Indian Ocean great waves washed over the Indonesian province of Acer, Thai sea resort of Phuket, as far north to Bangladesh and west to Madagascar.
Tsunami warning was issued in the eastern provinces of the Philippines when Chile was hit by an earthquake of high intensity. However, it is highly unlikely that great waves from South America can hit our eastern seaboard without warning. Nor it would hit us at all. Chile is too far, the tsunami forces will be dissipated by the time it reaches us. It cannot just sneak up on us; it has to pass South Pacific Islands. However authorities have to take precautions.
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