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Inside Earth 1-4
6th Grade Study Cards
Question | Answer |
---|---|
______ _______ __________ system is more than 50,000 kilometers long. An undersea mountain chain where new ocean floor is produced; a divergent plate boundary--see p. 24. | Mid-Ocean Ridge |
In _____-______ ________, the sea floor spreads apart along both sides of a mid-ocean ridge as new crust is added. As a result, the ocean floors move like conveyor belts, carring the continents along with them. | Sea-Floor Spreading |
What is unusual about Iceland? | It is a part of the mid-ocean ridge that rises above the surface in the North Atlantic Ocean. A steep-sided valley splits the top of some mid-ocean ridge. |
What is the process of sea-floor spreading? | Sea-floor spreading begins at a mid-ocean ridge, which forms along a crack in the oceanic crust. Along the ridge, molten material that forms along a crack in the oceanic crust. Along the ridge see p. 25 |
Evidence from magnetic stripes | Scientist discovered that the rock that makes up the ocean floor lies in a pattern of magnetized stripes. |
Evidence from Molten Material | Scientists dived into the ocean floor. In a ridge's central valley, the found strange rocks. These rocks form only when molten material hardens quickly after erupting under water. This has happened many times. |
Evidence from Drilling samples | Supports Sea-Floor spreading--The Glomar Challenger did drilling to study sea floor samples. They found that the farther away from a ridge the samples were taken, the older the rocks were. The youngest rocks were always in the center of the ridge. |
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 p. 28. |
A device that determines the distance of an object under water by recording echoes of sound waves. | sonar |