| A | B |
|---|
| deep-ocean trench | a deep valley along the ocean floor beneath which oceanic crust slowly sinks toward the mantle |
| mid-ocean ridge | undersea mountain chain where new ocean floor is porduced, divergent plate boundary- longest mountain range |
| sea-floor spreading | theprocess by which molten material adds new oceanic crust to the ocean floor |
| subduction | the process by which oceanic crust sinks beneath a deep ocean trench and back into the mantle as a convergent plate boundary |
| sonar | device that uses sound waves to measure the distance to an object |
| the farther away from the ridge the ________the rock is | older |
| rock closest to the ridge is the ____________ rock | youngest |
| Alvin | a small submarine that explored the ocean floor |
