pangaea
Since it's early beginnings some 4.6 billion years ago, the earth has been constantly changing its face. Oceans have become deserts and what was once mountainous terrain has found itself submerged in salt water oceans. Underwater volcanoes create new surfaces daily which one day may host a new species of life. It is this metamorphic nature of the earth that interests geologists and paleontologists the world over. What was the appearance of the primitive earth? What changes must have taken place that resulted in the earth we know today? These are some of the questions that scientists have been addressing for years. There has been much speculation about the structural origins of the earth. The most thought-provoking being the idea that at one stage in the earth's history all the continents were joined together to form a single mass of land. Francis Bacon first hypothesized the idea in the 1620's, focusing on the parallel shores of South America and Africa. But it wasn't until 1910 when Alfred Wegener scientifically considered the matter of a "supercontinent" which he called Pangea (Stokes, 1973). Since this time, scientists have argued for and against Wegener's explanation of Pangea. Today skeptics still argue the idea eve
Further support for Pangea comes from cross-sectional studies of rock strata. Researchers have identified similar layers of earth in regions of Antarctica, Australia, South America, Africa and India. These core samples display identical "banding" consisting of layers of basalt, sandstone/shale, coal and glacial till (refer to figure). It seems unlikely that identical rock sequences could have formed independently on separate masses of land and at the same time. It is reasonable to conclude that these rock patterns developed on a single mass of land that existed early in the history of the earth (internet). Wegener first envisioned that the landmass of Pangea split apart and assumed the current continental positions. The driving force behind this magnificent change was what Wegener called continental drift. As geological evidence to support the idea of continental drift he used the good "fit" of South America and Africa (Stokes, 1973), which suggests that the two continents used to be joined or were in close proximity to one another. Opponents to continental drift believed that there was no mechanical mechanism capable of moving landmasses as large as continents. The idea of huge bodies of rock plowing through the earth's crust was ridiculous. It wasn't until 1960 when Harry H. Hess hypothesized that cracks in the sea floor open along the crest of mid-ocean ridges where new sea floor forms and spreads out laterally on either side of the crest. Robert S. Dietz took Hess's ideas further, naming the process "sea floor spreading"(which occurs at 'spreading zones') and coupling it with the idea that old sea floor is absorbed beneath zones of deep ocean trenches and young mountains (Briggs, 1987). Dietz's idea of plates being absorbed into the asthenosphere at subduction zones (areas of converging plates) answered many questions. Since the earth maintains a constant size, it only seems logical that sprea
Some common words found in the essay are:
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Approximate Word count = 1293
Approximate Pages = 5 (250 words per page double spaced)
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