<p>Eighth Grade Science Earth’s History Study Guide</p><p>1. What is a plate boundary? Edge of the tectonic plate (border of lithospheric plate)</p><p>2. What is continental crust made of? Granite</p><p>3. What is oceanic crust made of? Basalt</p><p>4. Who proposed the theory of continental drift? Alfred Wegner</p><p>5. Why did scientists NOT support the theory of Continental Drift? Wegner could NOT explain how or why the plates moved.</p><p>6. What is subduction? When one plate goes under another plate and it is melted back into the mantle.</p><p>7. The Earth’s plates are made of what layer(s)? </p><p> inner core, outer core, mantle (asthenosphere—upper mantle), crust (lithosphere)</p><p>8. Explain convection currents. </p><p>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.</p><p>9. What does convection mean? Convection means the transfer of heat in a fluid (gas or liquid)</p><p>10. What material forms the mid-ocean ridges? Molten material (magma coming out, lave cooling on the surface) </p><p>11. Explain what type of plate movement is happening in each picture below. Then tell the NAME of that plate boundary. [Type text] [Type text] [Type text]</p><p>12. Which layer of the mantle is most flexible, often called soft and semi-rigid? Asthenosphere</p><p>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.</p><p>14. List the 3 pieces of evidence for Wegner’s theory of Continental Drift. Fossils, Rock layers, and Ancient Glacier</p><p>15. What does rifting mean and at what type of plate boundary does it happen? Rifting means tearing or pulling apart (Divergent Boundary)</p><p>16. What is Pangaea? The supercontinent about 200 million years ago</p><p>17. List the layers of the Earth from most dense to least dense? Inner core, outer core, mantle, crust</p><p>18. What layers of the Earth make up the lithosphere? Crust and upper mantle Eighth Grade Science Earth’s History Study Guide</p><p>19. Label the layers of Earth in the picture below. 20. Which layer of the Earth is made up of liquid iron and nickel? Outer core</p><p>21. Which process is responsible for destroying rock/crust? subduction</p><p>22. What do we call the chain of underwater mountains that are forming where sea-floor spreading is occurring? Mid Ocean Ridge</p><p>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.</p>