1. What is the lithosphere?  How are its boundaries defined?  On what evidence is its existence based?
2. How is sea floor topography inferred from studies of gravity over the ocean?
3. Is Earth’s mantle beneath the plates liquid or solid? Explain.
4. How deep are the deepest earthquakes at mid-ocean ridges? At transform faults? At subduction zones?
5. How is the asthenosphere different from the lithosphere?
6. What is the relation among lithosphere, asthenosphere, oceanic crust and oceanic mantle?
7. How much does temperature increase across the 100 km thick lithosphere, how much across a 100 km thick boundary layer at the base of the mantle, how much across the rest of the mantle?
8. What are the average thicknesses of the oceanic crust, continental crust, mantle, and lithosphere? 
9. What is the average water depth above old oceanic crust.
10. What are the slowest and fastest well-documented rates of present seafloor spreading?  Where do they occur?
11. What's the depth of a typical mid-ocean ridge crest in the Atlantic?
12. Describe the relationship between heat flow and age of oceanic lithosphere. Be as quantitative as possible.
    
    Solution

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