Earth!

2. sudden and violent shaking of the ground that can end up causing great destruction
6. the sideways and downward movement of the edge of a plate of the earth's crust into the mantle beneath another plate
8. the thick part of the earth's crust that forms the large landmasses
11. edges where two plates meet
12. where two tectonic plates separate
14. the thin part of the earth's crust which is under the ocean basins
15. first person to formulate the idea of continental drift
16. the mostly solid mass of earth's interior
18. the liquid innermost part of the earth
19. a large elevation of the earth's surface rising above the surrounding level
20. where two tectonic plates slide against each other

1. 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
3. the tough outer part of the earth
4. a long narrow ditch
5. a large extended depression with steep walls
7. made up of mostly iron and nickel that is on top of the inner core and underneath the mantle
9. giant irregularly shaped solid piece of rock
10. the movement of tectonic plates over geological time
13. where two tectonic plates meet
17. the rigid outer part of the earth made up of the crust and upper mantle