Earth!

2. made up of mostly iron and nickel that is on top of the inner core and underneath the mantle
4. a large extended depression with steep walls
5. the rigid outer part of the earth made up of the crust and upper mantle
6. the upper layer of the earth's mantle, below the lithosphere, in which there is low resistance to plastic flow and convection is thought to occur
8. the movement of tectonic plates over geological time
12. where two tectonic plates separate
13. the tough outer part of the earth
16. the sideways and downward movement of the edge of a plate of the earth's crust into the mantle beneath another plate
18. the mostly solid mass of earth's interior
19. the thick part of the earth's crust that forms the large landmasses
20. sudden and violent shaking of the ground that can end up causing great destruction

1. the thin part of the earth's crust which is under the ocean basins
3. edges where two plates meet
7. where two tectonic plates slide against each other
9. where two tectonic plates meet
10. the liquid innermost part of the earth
11. a large elevation of the earth's surface rising above the surrounding level
14. a long narrow ditch
15. first person to formulate the idea of continental drift
17. giant irregularly shaped solid piece of rock