Plate Tectonics Theory

Plate Tectonics Theory

The theory of plate tectonics proposes that Earth's outer shell consists of individual plates that interact in various ways and thereby produce earthquakes, volcanoes, mountains, and the crust itself.

Continental Drift

A hypothesis that originally proposed that the continents had once been joined to form a single supercontinent; The supercontinent broke into pieces, which drifted into their present-day positions.

Plate Tectonics Theory v. Continental Drift

Continental drift is not true; continents do not move across the face of the earth like Wegener proposed ( there was a supercontinent named Pangaea, though) rather the plates on which continents are located, move.

Evidence For Plate Tectonics Theory

Paleomagnetism: The natural remnant magnetism in rock bodies; the permanent magnetism acquired by rock that can be used to determine the location of the magnetic poles at the time it became magnetized. Rocks that were formed millions of years ago have a different polarity then ones forming today because the magnetic poles switch periodically.

Earthquake Patterns: Scientist found a close link between deep-focus earthquakes and ocean trenches. Also, the absence of deep-focus earthquakes along the oceanic ridge system was shown to be consistent with the new theory. In the plate tectonics model, deep-ocean trenches are produced where cool, dense slabs of oceanic lithosphere plunge into the mantle. Shallow-focus earthquakes are produced as the descending plate interacts with the lithosphere above it. As the slab descends farther into the mantle, deeper-focus earthquakes are produced.

Ocean Drilling: The data on the ages of seafloor sediment (The Deep Sea Drilling Project from 1968-1983) confirmed what the seafloor spreading hypothesis predicted. The youngest oceanic crust is at the ridge crest and the oldest oceanic is at the continental margins.

Hot Spots: Hot spot evidence supports the idea that the plates move over Earth's Surface. Ex. The Hawaiian Islands were formed when the Pacific plate moves over a volcanic area or hot spot.

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