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Plate Tectonics Test Study Guide
Block:
This is optional to complete. If you do complete this, your answers much be on a separate sheet of attached paper.
1.
Who developed the theory of continental drift?
Alfred Wegner
2.
What is the theory of continental drift?
The theory that the continents have not always been in their present positions and have moved
3.
What are the 4 pieces of evidence used to support the theory of continental drift and how does each support the theory that the continents moved?
1.
Puzzle fit of continents – indicate that they “fit” together
2.
Rock formation – the edges of the continents that “fit” together have the same type of rock formations AND mountain ranges connected when moved together
3.
Fossils – fossils from the same species are found on separate continents – the same species is not on two separate continents so at one time the 2 continents must have been 1 continent
4.
Climate evidence – Rock show evidence of glaciers in places that are today tropical – must have not been at their present positions for that type of climate
4.
Why was the theory of continental drift rejected?
No explanation for how they moved could be found
5.
.What are the oldest portions of the continents called? cratons
6.
Since the time of Pangaea, the shapes of the continents have changed. What are the 4 ways that the continents can grow/change shape? Explain each.
1.
Deep sea sediments – scraped off onto continent during convergent O-C subduction
2.
Igneous rock – volcanoes erupt and add new rock
3.
River sediments – deposited at the deltas where rivers flow into the ocean
4.
Terranes – when ocean “closes”, land between becomes attached to the new continent
7.
What is the theory of plate tectonics?
The theory that the Earth’s lithosphere is split into pieces called tectonic plates that move and interact at their edges
8.
How does the movement of the magnetic pole support the theory of plate tectonics? the position of the magnetic north pole in the past indicated by each continent matches up when they are moved from their current position
9.
Describe the process of seafloor spreading from oceanic crust creation to destruction.
A divergent boundary in the middle of the ocean causes the crust to pull apart. Magma fills the slit and hardens creating new seafloor. This seafloor is pulled in opposite directions. Eventually this new seafloor meets another plate and is subducted, melted, and destroyed.
10.
On the ocean floor, the thickness of the sediments INCREASEs with increasing distance from the ridge. Explain how seafloor spreading explains this.
The longer the seafloor has existed, the thicker the sediments would be that settle on the seafloor over time

11.
On the ocean floor, the age of the seafloor becomes older with increasing distance from the ridge. Explain how seafloor spreading explains this.
New seafloor is created at the ridge and pulled away from the ridge
12.
On the ocean floor, there is a mirror image of magnetic striping on either side of the mid-ocean ridge. Explain how seafloor spreading explains this.
When new seafloor cools, it preserves the position of the magnetic north pole at the time it cooled. As the seafloor is pulled apart in opposite directions, it creates a mirror image
13.
Where are earthquakes found in relation to plate boundaries?
Near the boundaries
14.
What are hot spots? How do hotspots support plate tectonic theory which states that the ocean floor is moving?
Hot spots are places away from plate boundaries where magma comes up to the surface creating a volcano.
As the plate moves, the volcano seems to move but it is really the plate. The line-up of volcanoes created becomes older the further you get from the currently active one
15.
Describe the 2 types of divergent boundaries and what occurs at each.
O-O – Spreading forming new oceanic crust, mid-ocean ridge at center
C-C – same as above, except rift valley at center
16.
Describe the 3 types of convergent boundaries and what occurs at each.
C-C – folded mountains
O-C-Coastal volcanic mountain range
O-O – volcanic island chain (arc)
17.
Describe a transform boundary.
Plate slide past each other, no crust created or destroyed
18.
Compare and contrast the 3 possible processes that move tectonic plates: convection currents, ridge push, and slab pull.
All explain movement
Convection currents – convection in the asthenosphere push the lithosphere plates around from friction on the bottom
Ridge push – the pushing up at the ridge and the sliding downward with gravity causes the movement of everything
Slab pull – the subducting plate is “pulled” into the mantle causing the movement of all the plates