| A | B |
|---|
| crust | outermost layer of the Earth |
| mantle | middle layer of the Earth |
| outer core | liquid layer of the Earth's core |
| inner core | solid, dense center of Earth |
| asthenosphere | soft layer of mantle on which tectonic plates move |
| lithosphere | outermost, rigid layer of the Earth divided into tectonic plates |
| mesosphere | strong, lower part of the mantle |
| tectonic plates | pieces of the lithosphere that move around on top of the athenosphere |
| continental drift theory | theory that the continents can move apart from one another |
| sea-floor spreading | process by which molten material adds new oceanic crust to the ocean floor |
| mid-ocean ridges | created by sea-floor spreading at a divergent boundary |
| convection | process by which hot material from deep within the Earth rises while cooler material near the surface sinks |
| convergent boundary | when two tectonic plates push into one another |
| divergent boundary | when two tectonic plates move away from one another |
| transform boundary | when two tectonic plates slide past each other horizontally |
| subduction | the movement of one tectonic plate under another |
| folding | rock layers bend due to stress in the Earth's crust |
| fault | a break in the Earth's crust where blocks of crust slide relative to each other |
| deformation | change in the shape of rocks in response to stress |
| strike-slip fault | a fault in which the two fault blocks move past each other horizontally |
| compression | stress that occurs when an object is squeezed, as when two tectonic plates collide |
| epicenter | point on the Earth's surface directly above an earthquake's starting point |
| focus | the point inside the Earth where an earthquake begins |
| rift | a deep crack that occurs as tectonic plates separate |
| hot spots | places on the Earth's surface that are directly above columns of rising magma, where volcanoes form |
