Chapter 7 Vocabulary

1. is the denser plate sinks below the more buoyant plate.
5. is the circulation of material caused by differences in temperature and density.
7. plate boundaries form where two plate collide.
8. plate boundary forms where two plates separate
9. drift suggested that continents are in constant motion on the surface of Earth.
12. is the cold and rigid outermost rock layer.
14. reversal occurs in the magnetic field reverses directions.

2. plate boundary forms where two plates slide past each other.
3. polarity a state in which magnetized objects would reverse direction and orient themselves to point south.
4. ridges the mountain ranges in the middle of the oceans.
6. continents were once part of a super continent.
10. polarity is a state in which magnetized objects, such a compass needles, will orient themselves to point north.
11. tectonics is Earth's surface is made of rigid slabs of rock, or plates, that move with respect to each other.
13. spreading is the process by which new oceanic crust forms along a mid-ocean ridge and older oceanic crust moves away from the ridge.