Essay by PaperNerd ContributorHigh School, 12th grade December 2001

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Key 1) Continental Drift Theory.

1915-Pangea Alfred Wagner played a major role in this theory.

The theory involved South America and Africa, and Wegner's hypothesis was that 200 million years ago, the continents were all one big enormous continent called Pangea, which after a while began to break into smaller continents. Two pieces of evidence that support this philosophy: the distribution of fossils between each continent, and the way South America and Africa fit together. Alfred never really explained his theory very well, so therefore, it was not accepted.

2) Polar wandering Polar wandering was a study of lava flow conducted in Europe in the 1950s. The discovery was that magnetic alignment in the iron rich minerals in lava flows of different ages was found to vary widely.

3) Continental Shelf "Fit" noticed.

1960s The Continental shelf is a gently submerged surface extending from the shoreline towards the deep- ocean basin.

The continental shelf is located 500 meters down, and the fit is not believed to be perfect, because after a long time erosion processes modify shorelines.

4) Magnetic Stripes found on the seafloor.

Otherwise known as magnetic reversals.

1963 The relationship between magnetic reversals and seafloor spreading is when a rock is the same age and distance from the ridge it turns out to have the same polarity. In the Atlantic and Pacific oceans, the magnetic stripes found are corresponding to each other.