who was alfred wegener
german scientist who suggested the idea of pangea and continential shift (continents shift apart over time)
what supported Wegener continential shift theory
1. the shape of the continents
2. plant and animal fossils found is south america matched those of found in africa. Wegener suggested that the similarities between the fossils found in both areas could only be explained by the fact that at one point in time they must have lived side by side.
3. also found similar rock in south america and aftrica and explained at one point they must have been joined together.
Describe sea floor spreading
1. Magma, which is molten rock, pushes up through earths crust under the ocean.
2. As magma cools, it forms new crust
3. More magma comes up, pushes the new formed crust to the side causing spreading of the sea floor.
what is the force that moves earth's plates
1. liquid mantle is heated, heated liquid is lighter and will rise.
2. the heated mantle rises above cooler liquid
3. As the heated liquid rises it cools.
4. When it cools, it begins to weigh more and will sink
5. In a cycle type manner, mantle is constantly heated, rises, cools, sinks creating convection currents.
How do the tetonic plates move
when the mantle moves, the plates floating on it also move.