THEY+1.4

toc =1.4 Sea-Floor Spreading=


 * Mid-Ocean Ridge:** The undersea mountain chian where new ocean floor is produced;a divergent plate boundary.
 * Sonar:** A system that determines the distance of an object under water by recording echoes of sound waves; get its name **sound waves** navigation and ranging.
 * Sea-Floor Spreading:** The process by which molten material adds new oceanic crust to the ocean floor.
 * Deep- Ocean Trenches:** A deep valley along the ocean floor through which oceanic crust slowly sinks towards 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.

Mapping the Mid-Ocean Ridge

 * The East Pacific rise is a part of the mid-ocean ridge

Evidence For Sea-Floor Spreading

 * Evidence from molten material
 * Evidence from magnetic stripes
 * Evidence from drilling samples

**Subduction at deep-ocean trenches**

 * Subduction in the Pacific Ocean
 * Subduction in the Atlantic Ocean