KHKZ+1.4

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=**1.4 Sea-Floor Spreading**=

**Vocabulary**

 * sea-floor spreading**-the process of continually adding new material to the ocean floor. (see diagram)
 * deep-ocean trenches**- a deep underwater canyon where the sea-floor goes back into the mantle.
 * subduction**- the process of when the ocean floor sinks back into the mantle.
 * sonar-** a device that bounces sound waves off underwater objects
 * Mid-ocean ridge**- the longest chain of underwater mountains

Mapping the mid-ocean ridge

 * Evidence from sea floor spreading
 * evidence from molten material
 * evidence from magnetic stripes
 * evidence from drilling samples
 * older rock pushed to sides

Subduction and Earth's ocean
subduction in the Pacific ocean


 * subduction in the Atlantic ocean