| A | B |
|---|
| Alfred Wegener | German scientist who hypothesized that all the continents were once joined together in single landmass called Pangaea |
| Harry Hess | Amerian geologist who proposed the idea of sea-floor spreading |
| Pangaea | the large landmass or the one "supercontinent" that is believed to have connected all the continents |
| continental drift | the hypothesis that the continents were once all connected in a single landmass and have since moved apart |
| convergent boundary | the place where two plates come together or converge resulting in a collision |
| deep-ocean trench | a deep valley along the ocean floor through which oceanic crust slowly sinks towards the mantle |
| divergent boundary | the place where two plates are moving away from each other; new crust is formed |
| fault | a break in Earth's crust wher rocks slide past each other |
| fossil | a trace of an ancient organism that has been preserved in rock |
| mid-ocean ridge | a long mountain range on the ocean floor |
| plate tectonics | a theory that statespieces of Earth's lithosphere are in slow constant motion driven by convection currents in the mantle |
| tectonic plates | sections of the lithosphere that move slowly over the asthenosphere |
| rift valley | a deep valley which forms along a divergent boundary |
| scientific theory | a well tested concept that explains a wide range of observations |
| sea-floor spreading | the process by which new ocean floor is continually being formed as magma rises to the surface and hardens as rock |
| sonar | a device that bounces sound waves off underwater objects and then records the echoes of these sound waves |
| subduction | the process by which ocean floor (oceanic crust) sinks beneath a deep-ocean trench and back into the mantle |
| subduction zone | the area where the denser plate goes under the less dense plate and sinks into the mantle |
| transform boundary | place where 2 plates slip past each other moving in opposite directions |
