6.1) Evidence for Plate Tectonics Flashcards
What is the theory of plate tectonics?
The theory of plate tectonics states that the Earth’s outer layer is divided into 15 massive pieces called tectonic plates
What are the 3 theories of plate tectonics?
- Divergent plate boundaries: the two plates move away from each other
- Convergent plate boundaries: the two plates move towards each other
- Transform plate boundaries: the two plates slip past each other
What was Alfred Wegener’s theory?
Wegener proposed that the continents once had been joined in one large landmass called Pangaea but then split apart and the continents moved to their current position
What are the three evidences that support Wegener’s theory?
- The continental shelves of continents fit together perfectly
- Identical rock formations on either side of the Atlantic Ocean
- Identical plant and animal fossils on different continents, separated by oceans
What is continental drift?
the movement of continents due to the motion of tectonic plates
Continents moving over time
What is seafloor spreading?
Seafloor spreading is a geologic process in which tectonic plates split apart from each other
When does seafloor spreading happen?
Seafloor spreading happens when molten rock rises up from the mantle at mid-ocean ridges and solidifies to form the new oceanic lithosphere
What did Harry Hess propose about Seafloor Spreading?
Hess proposed that a new rocky crust was being formed at ocean ridges and spreading outwards. This process is known as seafloor spreading
What did Harry Hess propose about subduction?
Hess proposed that crust was sinking into the Earth forming ocean trenches. This process is known as subduction
What are the four major evidences for seafloor spreading?
- Rift valleys
- Magnetic striping
- Age of the seafloor
- Sediment thickness
What is a rift valley?
A rift valley is a lowland region that forms where Earth’s tectonic plates move apart. This is evidence of seafloor spreading
What is magnetic striping?
Magnetic Striping is when the sea floor is spreading and magma from the mantle is rising through the Earth’s crust
What do molten rocks do when they cool in regards to their magnetic field direction ?
When molten rocks cool, they lock in their current magnetic field direction
What type of field does Earth have?
The Earth has a magnetic field
What happens the magnetite particles when molten rocks solidify?
When molten rock solidifies, all the magnetite particles in it line up with the Earth’s magnetic field
