| Term |
Definition |
| Crust |
The outermost layer of the Earth is the crust. |
| Mantle |
The layer of rock between the crust and the core is the mantle. |
| Core |
The central part of the Earth below the mantle. |
| Lithosphere |
The outermost, rigid layer of the Earth. |
| Asthenosphere |
A plastic layer of the mantle on which the pieces of the lithosphere moves. |
| Mesosphere |
Beneath the asthenosphere is the strong, lower part of the mantle. |
| Tectonic plates |
A block of lithosphere that consist of the crust and the rigid, outermost part of the mantle. |
| Continental drift |
The hypothesis that states that the continents once formed a single landmass, broke up, and drifted to their present locations. |
| Sea-floor spreading |
The process by which new oceanic lithosphere forms as magma rises toward the surface and solidifies. |
| Plate tectonics |
The theory that explains how large pieces of the Earth outermost layer, called tectonic plates, move and change. |
| Convergent boundary |
The boundary formed by the collision of two lithosphere plates. |
| Divergent boundary |
The boundary between two tectonic plates that are moving away from each other. |
| Transform boundary |
The boundary between tectonic plates that are sliding past each other horizontally. |
| Compression |
Stress that occurs when forces act to squeeze an object. |
| Tension |
Stress that occurs when forces act to stretch an object. |
| Folding |
The bending of rock layers due to stress. |
| Fault |
A break in a body o& rock along which one block slides relative to another. |
| Uplift |
The rising of regions of the eartha??s crust to higher elevations . |
| Subsidence |
The sinking of regions of the eartha??s crust to lower elevations. |
