Inside Planet Earth: Modern Scientific Beliefs
About the modern scientific beliefs about the inside of planet Earth, the earth onion, layers over a molten core, opinions on earth's creation, experiments and volcanoes.
WHAT DOES MODERN SCIENCE SAY?
The Earth Onion. Modern scientists have come to conclusions about the interior of the earth through seismology (the science of interpreting earthquake waves), geodetic and astronomical surveys, and subsurface heat-flow measurements. They pretty much agree on the following facts about the earth which, like an onion, is made up of layers. The crust is a thin skin, from 2 to 25 mi. thick, made up of granite in continental areas and of sedimentary rock layers under much of the ocean. The mantle, which lies beneath the crust, is composed of a basalt layer nearly 1,800 mi. thick. The outer core is liquid, molten because of the great internal heat. The inner core, still very hot (from 3,700 deg F. to 7,000 deg F.), is iron, solid because of the great pressure exerted at that depth (27,400 tons per sq. in.). To account for the earth's great weight (6 sextillion, 588 quintillion short tons), the core must be very dense.
The inside of the earth is probably still heating up from the radioactive decay of uranium, thorium, and potassium.
Fiery Ball or Dust Collector? Scientists differ on the subject of how the earth was formed. Some think that it was once a molten ball, ejected by a star, and that it is slowly cooling down. Others think that it formed from the accumulation of stellar dust and is slowly heating and expanding. Dr. K. M. Creer, a British physicist, believes he has evidence that the earth is expanding like a balloon and is now nearly twice its original size. He thinks that continents once covered the earth's entire surface. It is true that the configuration of the eastern coast of South America could fit almost perfectly against the western coast of Africa, and that there is a similar fit between the North American and Greenland coasts and that of western Europe. Creer suggests that when the earth was about a billion years old, expansion caused the shell to crack open and that the 2 sides of the crack have been drifting apart ever since (3 1/2 billion years). This crack has been filled by the Atlantic Ocean.
Volcanoes. From volcanic lava, which originates a few miles to 100 mi. below the surface, we can tell that the earth's interior is very hot (2,000-3,000 deg F.), and that it contains homogenous material.
Man-made Holes in the Earth. In deep well borings, the temperature rises about 16 deg F. per thousand feet initially, but this rate decreases as lower depths are reached.
Recently man has been attempting to pierce the earth's crust to determine more about the earth's origin and composition. One of the most ambitious projects was Project Mohole, named after the Moho discontinuity (the place where crust and mantle meet). Through Project Mohole, a deep-sea drilling operation near Hawaii, the U.S. hoped to reach the mantle at a depth of 17,000'. However, the project was canceled in 1961, when borings had reached only 1,035'. Since then, the Russians, the French, and the Americans have launched other projects. One of the most recent is FAMOUS (French-American Mid-Ocean Undersea Study), which includes deep drilling by Global Challenger, a ship set up for that purpose. These studies have lent credence to the theories that the oceans are shrinking and that the continental shelves are shifting, but no evidence has been found of a hollow earth.
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