| Term |
 |
|
| Definition |
|
|
| Pangea |
The name of the single landmass that broke apart about 300 million years ago to create today's continents. |
| continental drift |
The hypothesis that the continents slowly move across Earth's surface. |
| fossil |
Any trace of an ancient organism preserved in rock. |
| mid-ocean ridge |
The longest chain of mountains in the world found under the sea where ocean floor is produced. |
| sonar |
A system that determines the distance of an object under water by recording echoes of sound waves. |
| sea-floor spreading |
The process by which molten material adds new oceanic crust to the ocean floor. |
| deep-ocean trench |
Deep underwater canyons on the ocean floor where crust slowly sinks toward the mantle |
| subduction |
The process by which the ocean floor sinks beneath a deep-ocean trench and back into the mantle. |
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