Plate Tectonics:

Evidence for Continental Drift:

Vocabulary:

Sea-floor spreading, magnetometer

Continental Drift:

Evidence:

The evidence which gave rise to the theory of continental drift -- more correctly called plate tectonics -- includes the following:

* The coasts of the continents surrounding the Atlantic Ocean could, if the continents were moved closer, fit together like a jigsaw puzzle.

* Living animals in widely separated lands are similar. For example India and Madagascar have similar mammals, which are quite different from those in Africa, even though it is now near to Madagascar.

* Fossil plants in India, South Africa, Australia, Antarctica and South America are similar to each other. This so-called Glossopteris flora is quite different from plants found in other parts of the world at the same time.

* The same applies to fossil animals.

* There are numerous geological similarities between eastern South America and western Africa.

* Apparent Polar Wandering: Paleomagnetism tells us how far from the poles rocks were when they formed, by looking at the angle of their magnetic field. The story told by different continents is contradictory, and can only be explained if we assume the continents have moved over time.

* There are ridges in the floors of the main oceans.

* Paleomagnetism shows that the sea floor has spread away from these ridges. Distinct patterns of stripes can be seen in the magnetism of rocks on either side of the ridges.

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Sea Floor Spreading