Plate Tectonics Flashcards
What did Wegener’s continental drift hypothesis state?
Stated that the continents had once been joined to form a supercontintinent, Pangaea.
Wegener’s proposed that the supercontinent Pangaea began to break apart 200 million years ago and formed the present landmasses.
Describe the breakup of Pangaea. 250 Million years ago: 200 Million years ago: 100 Million years ago: 50 Million years ago: Present:
250 Million years ago: Pangaea consisted of all the major continents
200 Million years ago: The rifting that eventually resulted in the Atlantic Ocean occured over an extended period of time. The first rift developed between North America and Africa.
100 Million years ago: Continued rifting of the southern landmasses sent India on a northward journey.
50 Million years ago: Australia began to separate from Antarctica.
Present: A modern map shows that India has collided with Asia, creating the Himalayas.
What are the 4 pieces of evidence for continental drift?
1) The Continental Puzzle
2) Matching Fossils
- Fossile vidence for continental drift includes several fossil organisms found on different landmasses.
3) Rock Types and Structures
- Rock evidence for continental drift exists in the form of several mountain belts that end at one coastline only to reappear on a landmass across the ocean.
4) Ancient Climates
- Stuff buried under would be similar.
Why was Wegener’s hypothesis rejected? What was the new theory?
Wegener could not provide an explanation of exactly what made the continents move. New technology lead to findings which then lead to the new theory called Plate Tectonics?
According the the plate tectonics theory, what does the uppermost mantle along with the overlying crust behave as?
A strong rigid layer known as the lithosphere.
What is a plate?
One of the numerous rigid sections of the lithosphere that move as a unit over the material of the asthenosphere.
What are the 3 types of plate boundaries? Describe.
1) Divergent boundaries- (also called spreading centers) are the places where two plates move apart.
2) Convergent boundaries- form where two plates move together.
3) Transform fault boundaries- are margins where two plates grind past each other without the production or destruction of the lithosphere.
What are the Divergent Boundaries?
1) Oceanic Ridges and Seafloor Spreading
- Oceanic ridges
- Rift Valleys
- Seafloor Spreading
2) Continental Rifts
What are oceanic ridges?
Continuous elevated zones on the floor of all major ocean basins. The rifts at the crust of ridges represent divergent plate boundaries.
What are rift valleys? Where do they develope?
Are deep faulted structures found along the axes of divergent plate boundaries. They can develop on the Seafloor or on land.
What is Seafloor spreading?
Produces new oceanic lithosphere.
What are continental rifts?
When spreading centers develop within a continent, the landmasses may split into two or more smaller segments, forming a rift.
What are the convergent boundaries?
Subduction zones
1) Oceanic-Continental
2) Oceanic-Oceanic
3) Continental-Continental
What are subduction zones?
Occurs when one oceanic plate is forced down int the mantle beneath a second plate.
What happens in an oceanic-continental convergent boundary?
Denser oceanic slab sinks into the asthenosphere and pockets of magma develop and rise.
