Plate Tectonics plate tect BN asf Wegeners theory

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 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/Hazard s/Plate. Tectonics/30_Sea. Floor. html

2. Age of rocks on the ocean floor • Rocks near the midocean 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.