science vocab

4. reversal The process by which earth's magnetic north pole and magnetic south pole switch positions periodically; a change in the direction in which earth's magnetic field points
6. A break in a body of rock along which one block moves relative to another
9. A block of lithosphere that consists of the crust and the rigid, outermost part of the mantle.
13. tectonics The theory that the earth's outer layer is made up of large, moving pieces called tectonic plates; the theory explains how plates interact and how those interactions relate to processes such as earthquakes and mountain building
14. spreading The process by which new oceanic lithosphere forms when magma rises to the earth's surface at mid-ocean ridges and solidifies, as older, existing seafloor moves away from the ridge
17. The soft layer of the mantle on which the tectonic plates move
18. The location within earth along a fault at which the first motion of an earthquake occurs
20. drift The hypothesis that a single large landmass broke up into smaller land masses to form the continents, which then drifted to their present locations; the movement of continents
22. The process by which one lithospheric plate moves beneath another plate as a result of tectonic forces
23. The edge between two or more plates classified as deverigant, con vergent, or transform by the movement taking place between two plates
24. The boundary between tectonic plates that are colliding

1. The sudden return of elastically deformed rock to its undeformed shape.
2. The solid, outer layer of the earth consists of the crust and the rigid upper part of the mantle
3. The layer of rock between the earth's crust and core
5. The central part of earth below the mantle
7. the bending, tilting, and breaking of earth's crust; the change in the shape of rock in response to stress
8. The boundary between two tectonic plates that are moving away from each other
10. A movement or trembling of the ground that is caused by a sudden release of energy when rocks along a fault move
11. The boundary between tectonic plates that are sliding past each other horizontally
12. the thin outermost layer of earth
15. The point on earth's surface directly above an earthquake's starting point, or focus
16. current Any movement of matter that results from differences in density; may be vertical, circular, or cyclical
19. The strong, lower part of the mantle between the asthenosphere and the outer core
21. system of ideas that explains many related observations and is supported by a large body of evidence acquired through scientific investigation