Plate Tectonics Flashcards
What does Wegener’s Theory describe
Continental Drift
Why did Wegener come up with his theory?
He came across some work, listing the fossils of very similar plants and animal which had been found on opposite side of the Atlantic Ocean
He also noticed that the coastlines of Africa and South America matched
What was the alternative theory on why similar fossils were found on either sides of oceans?
There had once been land bridges linking the continents - so animals had been able to cross. The bridges had been ‘sunk’ or covered since then
What was the evidence for Wegener’s theory?
1) Similar fossils were found on either sides of oceans
2) There were matching layers in the rocks fond in different continents
3) Fossils had been found in the ‘wrong’ place (tropic plants in the arctic)
What was Wegener’s theory of continental drift?
About 300 million years ago, there had been just one ‘supercontient’. This landmass, Pangaea, broke apart into smaller chuncks which moved apart. He claimed that these chuncks - modern day continents - were still slowly ‘drifting’ apart - hence continental drift
What did Wegener think was causing continental drift?
He thought the continents were ploughing through the sea bed, and that there movement was caused by tidal forces and the earth’s rotation
What did other scientists think about Wegener’s explanation for continental drift?
They said it was impossible. A scientist calculated that the forces needed to move the continents would also have stopped the earth rotating
Why were Wegener’s predictions for the speed at which the continents wildly wrong?
He had inaccurate data for his calculations
What happened to Wegener’s theory in the 1950s?
Scientists were able to investigate the ocean floor and found new evidence for his theory. He wan’t right about everything but the main idea was correct.
When was continental drift accepted? What do we know think about continental drift?
Geologists were convinced in the 1960s of continental drift. We now think Earth’s crust is made of several chunks called tectonic plates which move about, and that colliding chunks push the land up to create mountains
