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Section 4.4- Sea Floor Spreading Reading Notes 1. What is a mid-ocean ridge?

Section 4.4- Sea Floor Spreading Reading Notes 1. What is a mid-ocean ridge?. A mid-ocean ridge is an undersea mountain chain where new ocean floor is produced. 2. How did scientists map mid ocean ridges in the mid-1900’s?. Scientists used sonar to map mid ocean ridges in the mid-1900’s.

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Section 4.4- Sea Floor Spreading Reading Notes 1. What is a mid-ocean ridge?

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  1. Section 4.4-Sea Floor SpreadingReading Notes1. What is a mid-ocean ridge? A mid-ocean ridge is an undersea mountain chain where new ocean floor is produced.

  2. 2. How did scientists map mid ocean ridges in the mid-1900’s? Scientists used sonar to map mid ocean ridges in the mid-1900’s.

  3. 3. What is sonar? What is it used for? Sonar is a device used to determine the distance of an object under water by recording the echoes of sound waves.

  4. 4. In 1960, one scientist came up with the idea of sea-floor spreading. Explain what this is. Sea-floor spreading is when the sea floor spreads apart along both sides of a mid ocean ridge as new crust is added. The ocean floor moves like a conveyor belt and carries the continents along with them.

  5. 5. In sea-floor spreading, where does new crust come from? In sea floor spreading, new crust is formed when molten material erupts and cools.

  6. 6. What are three types of evidence for sea-floor spreading? Three types of evidence for sea-floor spreading are • Molten material • Magnetic stripes • Drilling samples

  7. 7. How did drilling samples show that sea-floor spreading really has taken place? The further away from the ridge the samples were taken, the older the rocks were. New rocks were always in the center of the ridges.

  8. 8. What are deep-ocean trenches? What important things happen there? Deep ocean trenches are underwater canyons. Subduction takes place there where part of the ocean floor sinks back into the mantle.

  9. 9. The Pacific Ocean is __________________. SHRINKING

  10. 10. Why is the Atlantic Ocean expanding? • The Atlantic Ocean only has a few short trenches. Therefore, the ocean floor continues to grow and expand through sea floor spreading.

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