Plate Tectonics plate tect BN.asf

Wegener’s theory of continental drift was not accepted because he did not have a good explanation or mechanism for how it worked. He used…

1. The fit of the continents The continents fit like puzzle pieces.

2. Fossils Fossils of the same dinosaur were found on different continents (South America and Africa). Fossils of the same plant were found in many different locations (Africa, Australia, India, South America and Antarctica).

3. Past Climate Conditions Fossils of warm weather plants were found in cold locations (like the Arctic Ocean) Evidence of glacial activity can be found in South America, Africa, India, and Australia.

4. Rocks and Common Geologic Features - Similar rock structures can be found in Greenland and the eastern U. S. and also in South America and Africa.

Plate Tectonics Developed around 1950 to explain the motion of the plates and the position of the continents. Further evidence was identified to support Wegner’s theory and a mechanism was discovered to explain how/why the plates move.

1. Seafloor Movement New land is added on the sea floor at divergent boundaries and as a result, the sea floor spreads apart. (Mid-ocean Ridges form at these divergent boundaries) http://www.suu.edu/faculty/colberg/Hazards/PlateTectonics/30_SeaFloor.html

2. Age of rocks on the ocean floor Rocks near the mid-ocean ridges are younger than those farther away

3. Paleomagnetism Over time the Earth’s magnetic poles have reversed. When the poles reverse, iron minerals align themselves with the Earth’s magnetic pole. Scientists have found rocks on the ocean floor that showed many magnetic reversals.

4. Locations of hot spots Hot spots are stationary Scientists can track the movement of a plate by looking at the position of a hot spot.

http://www. suu. edu/faculty/colberg/Hazards/PlateTectonics/18_Pangaea http://www.suu.edu/faculty/colberg/Hazards/PlateTectonics/18_Pangaea.html