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Science lessons 1-3
| Term | Definition |
|---|---|
| continental drift | The hypothesis that the continents slowly move across Earth's surface. |
| Pangaea | The name of the single landmass that began to break apart 200 million years ago and gave rise to today's continents. |
| fossil | The preserved remains or traces of an organism that lived in the past. |
| mid ocean ridge | An undersea mountain chain where new ocean floor is produced; a divergent plate boundary. |
| sea floor spreading | The process by which molten material adds new oceanic crust to the ocean floor. |
| deep ocean trench | A deep valley along the ocean floor beneath which oceanic crust slowly sinks toward the mantle. |
| subduction | The process by which oceanic crust sinks beneath a deep ocean trench and back into the mantle at a convergent plate boundary. |
| plate | A section of the lithosphere that slowly moves over the asthenosphere, carrying pieces of continental and oceanic crust. |
| divergent boundary | A plate boundary where two plates move away from each other. |
| convergent boundary | A plate boundary where two plates move toward each other. |
| transform boundary | A plate boundary where two plates move past each other in opposite directions. |
| plate tectonics | The theory that pieces of Earth's lithosphere are in constant motion, driven by convection currents in the mantle. |
| fault | A break in Earth's crust along which rocks move. |
| rift valley | A deep valley where two plates move apart. |