vocab

2. ridge-a long, seismically active submarine ridge system situated in the middle of an ocean basin and marking the site of the upwelling of magma associated with seafloor spreading. An example is the Mid-Atlantic Ridge.
6. hypothetical landmass that existed when all continents were joined, from about 300 to 200 million years ago
10. sideways and downward movement of the edge of a plate of the earth's crust into the mantle beneath another plate.
11. reversal-When magma rises to the Earth's surface at a mid-ocean ridge, it flows out onto both sides of the ridge, gradually cooled by the seawater

1. spreading-the formation of new areas of oceanic crust, which occurs through the upwelling of magma at mid ocean ridges and its subsequent outward movement on either side.
3. boundary-In plate tectonics, a divergent boundary or divergent plate boundary is a linear feature that exists between two tectonic plates that are moving away from each other. Divergent boundaries within continents initially produce rifts, which eventually become rift valleys.
4. boundary-A convergent boundary is an area on Earth where two or more lithospheric plates collide. One plate eventually slides beneath the other, a process known as subduction.
5. movement caused within a fluid by the tendency of hotter and therefore less dense material to rise, and colder, denser material to sink under the influence of gravity, which consequently results in transfer of heat.
7. boundary-A transform fault or transform boundary, is a fault along a plate boundary where the motion is predominantly horizontal. It ends abruptly where it connects to another plate boundary, either another transform, a spreading ridge, or a subduction zone.
8. drift-the gradual movement of the continents across the earth's surface through geological time.
9. tectonics-a theory explaining the structure of the earth's crust and many associated phenomena as resulting from the interaction of rigid lithospheric plates which move slowly over the underlying mantle.