Download Eighth Grade ScienceEarth`s HistoryStudy Guide

Eighth Grade Science
Earth’s History
Study Guide
1. What is a plate boundary? Edge of the tectonic plate (border of lithospheric plate)
2. What is continental crust made of?
3. What is oceanic crust made of?
Granite
Basalt
4. Who proposed the theory of continental drift? Alfred Wegner
5. Why did scientists NOT support the theory of Continental Drift? Wegner could NOT explain how
or why the plates moved.
6. What is subduction? When one plate goes under another plate and it is melted back into the
mantle.
7. The Earth’s plates are made of what layer(s)?
inner core, outer core, mantle (asthenosphere—upper mantle), crust (lithosphere)
8. Explain convection currents.
Fluids when heated become less dense and rise away from a heat source. Once the fluid is
away from the heat source, it cools, becomes MORE dense and sinks. This cycle continues
as long as there is a heat source.
9. What does convection mean?
Convection means the transfer of heat in a fluid (gas or liquid)
10. What material forms the mid-ocean ridges?
Molten material (magma coming out, lave cooling on the surface)
11. Explain what type of plate movement is happening in each picture below. Then tell the NAME of
that plate boundary.
Eighth Grade Science
Earth’s History
Study Guide
a. Divergent Boundary- pulling
apart
b. Convergent Boundary- pushing
together
c. Transform Boundary- sliding
past
12. Which layer of the mantle is most flexible, often called soft and semi-rigid? Asthenosphere
13. What is sea-floor spreading? When the two oceanic plates are pulling apart at a Divergent
Boundary and the magma comes to the surface. This lava then cools creating new sea floor.
14. List the 3 pieces of evidence for Wegner’s theory of Continental Drift.
Fossils, Rock layers, and Ancient Glacier
15. What does rifting mean and at what type of plate boundary does it happen?
Rifting means tearing or pulling apart (Divergent Boundary)
16. What is Pangaea? The supercontinent about 200 million years ago
17. List the layers of the Earth from most dense to least dense? Inner core, outer core, mantle,
crust
18. What layers of the Earth make up the lithosphere? Crust and upper mantle
Eighth Grade Science
Earth’s History
Study Guide
19. Label the layers of Earth
1.
2.
3.
4.
Crust
Mantle
Outer core
Inner core
in
the picture below.
20. Which layer of the Earth is made up of liquid iron and nickel? Outer core
21. Which process is responsible for destroying rock/crust? subduction
22. What do we call the chain of underwater mountains that are forming where sea-floor spreading is
occurring? Mid Ocean Ridge
23. Consider the diagram below. Tell which type of plate boundaries are present in the diagram and
describe what is happening at each plate boundary.