You answered your own question IN THE CENTER....
In the core.... and by the way, if you're planning on going there wear a bathing suit it is boiling hot there (like lava from a volcano, same kinda thing)
2006-06-06 12:06:26
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answer #4
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answered by chnuna 3
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In geology, continents are defined in terms of the earth's crustal structure and constituency, rather than land-surface areas. Geophysicists have studied these features by using seismography records of shock waves produced by earthquakes. Their data suggest that the center of the earth is a hot, dense, partly molten nickel-iron core more than 6000 km (more than 4000 mi) in diameter. Surrounding this core is a mantle of hot, solid rock, 3000 km (1800 mi) thick, a portion of which is semiplastic. This is enclosed, in turn, by the earth's outermost shell, the crust, a layer of relatively cool rock ranging in thickness from an average of 5-10 km (3-6 mi) beneath the oceans to 40 km (25 mi), on the average, beneath the continents.
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Continental Drift
This landmark Scientific American article from 1963 heralds a profound turning point in geology: the acceptance of continental drift, or plate tectonics theory. Canadian geophysicist J. Tuzo Wilson, one of the architects of modern geologic thought, summarized compelling evidence that the earth’s crust is a dynamic assembly of moving plates whose interactions explain most geological phenomena, including volcanoes and earthquakes. Wilson demonstrated the existence of a continuous, planetwide system of plate boundaries, evidenced by ridges on the ocean floor. As he predicted, the study of the ocean floors verified the theory of continental drift within a few years of this article. Wilson’s suggestion that slow convection currents within the earth’s interior drive the motions of the plates is still being debated.
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Beneath the oceans the crust consists of a single layer of dense, dark basaltic rock made up, in large part, of iron-magnesium minerals. On the continents, this layer is buried beneath a much thicker layer of lighter colored, less dense rocks made up of aluminosilicate minerals. Because of the difference in density, the lighter rocks “float” on the basaltic ones. By a principle known as isostasy, in those areas where the lighter rocks rise highest—such as the great mountain ranges—they also extend downward to greater depths; beneath these ranges, roots of light rocks extend downward into the dark rocks of the crust to depths that are appreciably greater than under the vast, flat plains that occupy the interior regions of most continents.
In the 1960s geologists began to uncover proof that the continents not only float—that is, move up and down within the crust—but that they also travel, or drift, laterally. The study of the history and origins of continental drift is called plate tectonics because, in charting the directions that the continents have taken, geologists discovered that the earth's crust and upper mantle are divided into a number of semirigid plates, each of which has recognizable boundaries and moves as a unit. Some of these tectonic plates (the Pacific plate, for example) consist almost entirely of oceanic crust; others, such as the North American and Eurasian plates, are made up of mostly continental crust. Plate boundaries are generally located in midocean or close offshore, but in a few places rise from the seabottom and extend across dry land. Western California, where the earthquake-prone San Andreas fault marks the boundary between the Pacific and North American plates, is one such place.
The land-sea patterns of today have evolved over the course of hundreds of millions of years, during which time continental landmasses drifted, were united by collisions, then torn apart and recombined. These movements show no sign of slackening or abating, so the distribution of sea and dry land will continue to change for as long as the planet contains the heat energy required to drive the movement of its crustal plates.
2006-06-06 12:16:42
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answer #6
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answered by khri-khri 1
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