Plate Tectonics Study Guide
1. Explain the theory of plate tectonics. Explain the 3 pieces of evidence that support the theory.
The theory of plate tectonics is that the Earth’s lithosphere is divided into tectonic plates that drift/float on the asthenosphere. Plates move by convection currents.
1. Continental Drift theory- plates fit together like puzzle pieces.
2. Sea-floor spreading- sea floor spreads at mid-ocean ridges
3. Magnetic Reversals- iron bands in the sea floor
2. Explain how convection currents move the plates apart. What 2 layers of the Earth are responsible for this?
Convection currents are when heat from the core heats the magma and the hot magma rises because it is less dense. Cooler magma sinks because it is more dense. The 2 layers are the lithosphere (tectonic plates) and the asthenosphere (thick, liquid magma)
3. Describe divergent plate boundaries: (oceanic-oceanic, oceanic-continental, continental-continental) Use a picture if possible to help explain.
Oceanic-Oceanic: 2 oceanic plates separate causing sea-floor spreading. A mid-ocean ridge is formed. This causes the ocean to get bigger.
Continental-Continental- 2 continental plates separate, this creates a rift (crack) that can fill with water and form a river. They do not separate completely, because continental crust is very thick.
4. Describe convergent plate boundaries: (oceanic-oceanic, oceanic-continental, continental-continental). Use a picture if possible to help explain.
Oceanic-Oceanic: 2 oceanic plates collide and can subduct (one plate slides under the other). It can create an underwater volcano or volcanic islands.
Oceanic-Continental: one oceanic and one continental plate collide and the oceanic crust subducts under the continental because oceanic crust is more dense. This creates volcanoes.
Continental-Continental: 2 continental plates collide to form mountains.
5. Describe transform plate boundaries: (oceanic-oceanic, oceanic-continental, continental-continental). Use a picture if possible to help explain.
2 plates slide past each other, forming an earthquake. Seismic waves are released during the movement.
6. What is subduction? Explain.
Subduction is when one plate slides under another plate. Usually the more dense sinks.
7. Explain what causes earthquakes. (Hint: what type of wave, where do they occur?)
Earthquakes occur at transform boundaries. When the plates slide, pressure builds up and rocks break, causing a fault. Seismic waves are energy waves that are released when the plates slide.
8. What is a hot spot? What has it formed?
A hot spot is an area of volcanic activity in the MIDDLE of a plate. The plate above the hotspot shifts and forms a chain of volcanoes.
Ex: Hawaii
9. What is the Ring of Fire? Explain what types of boundaries have caused this.
The Ring of Fire is a zone of frequent volcanic eruptions and earthquakes, mostly cause by subduction. It is located around the Pacific Plate.
10. Approximately how much do plates move in one year?
Centimeters per year
11. Using the picture below. Explain why North America and Europe are getting farther apart.
The North American Plate and the Eurasian are diverging (separating).
12. Draw a model of the 5 physical layers of the Earth. Explain how they are arranged.
*Arranged with the most dense layers in the middle and the least dense layers near the surface.
13. Draw a model of the 3 compositional layers of the Earth. Explain how they are arranged.
Crust- surface, least dense
Mantle
Core- center, most dense
14. What are the two types of crust? Which type is thicker?
Oceanic and continental crust. Continental crust is thicker.
15. Explain the difference between magma and lava?
Magma is a thick liquid in the mantle. When the magma reaches the earth’s surface (through a volcano), it becomes lava.
16. What percent of earth’s mass is the crust?
Crust is the thinnest layer (less than 1%)
17. What is the lithosphere? What is it divided into?
The lithosphere is the top layer of the mantle. It is divided into tectonic plates.
18. What is the asthenosphere? Explain how it relates to the theory of plate tectonics.
The asthenosphere is a thick moving liquid which moves due to convection currents. The tectonic plates float on this layer.
19. What are the two parts of the core? Which is liquid and which is solid? Why is the closest to the center solid?
Inner core- center, solid due to pressure
Outer core- liquid, iron spins
20. What is Pangaea? What evidence did you find from the Pangea lab to suggest that it did exist? Give at least two pieces of evidence.
Pangaea is the single continent according to Wegener.
1. Continents fit together like puzzle pieces.
2. Fossils on different continents
3. Rock formations on different continents.
21. What causes Earth’s magnetic field? Which layer of the Earth is responsible?
The spinning of iron in the liquid outer core.
22. What are magnetic pole reversals?
Magnetic pole reversals are when the Earth’s magnetic poles reverse (switch).