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CHSCheyScienceCh1Se4
Question | Answer |
---|---|
Mid-ocean ridge | The chain of mountains that extends into all of the oceans on Earth |
Subduction | The geological process by which the ocean floor sinks into the mantle |
Sea-floor spreading | The geological process that continually adds new material to the ocean floor |
Deep-ocean trench | a deep valley along the ocean floor through which oceanic crust slowly sinks toward mantle |
sonar | device that scientists use to map the ocean floor |
What evidence did scientists find for sea-floor spreading? | 1. molten material 2. magnetic stripes 3. drilling samples |
Evidence from molten material | Alvin's crew found rocks shaped like pillows/toothpaste. Such rocks only form when molten material hardens quickly after erupting underwater, showing molten material has erupted overandover along cen valley of ridge |
Evidence from magnetic stripes | scientists discovered that the rock that makes up the ocean floor lies in a pattern of magnetized "stripes". These stripes hold record of reversals in Earth's magnetic field |
Evidence from drilling samples | samples from sea-floor were brought up through drilling pipes, and rocks' ages were determined; discovered youngest rocks were always @ center of ridge |
Where is the oldest part of the ocean floor? | older oceanic crust lies further from mid-ocean ridge |