| A | B |
|---|
| fossil | trace or remains of plant or animal in sedimentary rock |
| continental drift | Wegener's hypothesis that Earth's continents had once been joined as a single landmass |
| Pangaea | The supercontinent which contained all the continents in one landmass |
| topographic | a map that shows the surface features of Earth |
| magnetometer | device, used to map the ocean floor, that detects small changes in magnetic fields |
| paleomagnetism | study of Earth's magnetic record using data gathered from iron-bearing minerals in rocks |
| magnetic reversal | changes in Earth's magnetic field over geologic time, recorded in ocean-floor rocks and continental basalt flows |
| isochron | line on a map that connects points of the same age |
| seafloor spreading | Hess's theory that new ocean crust is formed at mid-ocean ridges and destroyed at deep-sea trenches |
| tectonic plates | a slab of continental or oceanic crust |
| divergent boundary | place where two plates are moving apart |
| rift valley | long, narrow depression caused by stretched crust |
| convergent boundary | place where two plates are moving toward each other |
| subduction | when one of two plates is descending under the other |
| transform boundary | place where two plates slide horizontally past each other |
| involve | to contain or include as a part |
| asthenosphere | partially molten, plastic-like, flowing layer located below the solid part of Earth's mantle |
| ridge push | process where the weight of uplifted ridge is thought to push an oceanic plate toward a trench |
| slab pull | process where the weight of a subducting plate helps pull the lithosphere into the subduction zone |
| mechanism | an instrument or process, physical or mental, by which something is done or comes into being |
