Length: 5 Pages 1293 Words

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 argu Continue...

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Although not directly linked to the Pangea hypothesis, paleomagnetic data does support the theory of sea floor spreading which is one of the critical mechanisms of plate (continent) movement. Sea floor spreading has its own driving force called convection. Fossil, geologic and paleomagnetic data clearly validate Wegener's hypothesis- proving the existence of the super continent. These core samples display identical "banding consisting of layers of basalt, sandstoneshale, coal and glacial till (refer to figure). In 1963, Fred Vine and Drummond Matthews proposed that as lava erupts at 'spreading zones' and travels laterally away from the zone, it cools. The break up Pangea first began in the late Triassic, between North Africa and North America. Tuzo Wilson gave further credence to Dietz's sea floor spreading by observing that as one moves away from mid-ocean ridges the ages of oceanic islands increases. The resulting rift was thought of as a complete separation of Pangea into Northern and Southern parts termed Laurasia and Gondwanaland respectively. The end of the Triassic was marked with substantial extinctions among terrestrial vertebrates (Behrensmeyer et al. The result is the circular motion known as convection. Researchers have identified similar layers of earth in regions of Antarctica, Australia, South America, Africa and India. It is this circular motion that drives plate movement in either a diverging or converging manner. The idea of huge bodies of rock plowing through the earth's crust was ridiculous. 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). Early arguments for the existence of Pangea were based primarily on the 'good fit' model that results when the continents are pieced together, but scientists and skeptics alike needed more proof.