RLAF+1.4

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**Vocabulary**

 * Sonar:** device that uses the echoes of sound waves
 * Sea-floor Spreading**:the process that puts old rocks to the side and new ones in the middle.
 * Molten Material:** hot rock that erupts for the process of sea-floor spreading.
 * Magnetic Strips:** different patterns of magnets forming the earth's magnetic field.
 * Drilling Samples:** drilling in the ground to prove sea-floor spreading's existence.
 * Deep Ocean Trenches:** deep under-water canyons.
 * Subduction:** the ocean floor sinking to the mantle.

**Outline**

 * ===**Intro**===
 * Wegener's theory might be correct from evidence of sea-floor spreading.
 * "adding new material to ocean floor is called sea-floor spreading."Harry Hess said.

Evidence from Molten Material
 * ===**Evidence of Sea-Floor Spreading**===


 * cracked rocks on the ocean floor.
 * rocks shaped weirdly
 * rocks erupting through Central Valley of the Ocean Ridge.

Evidence from Magnetic Stripes


 * Earth's Magnetic Field changed 780,000 years ago.
 * Scientist discovered unique pattern.


 * Evidence from drilling samples
 * tested how old rocks were
 * noticed how all rocks on the side are older and rocks in the middle are much younger.


 * ===**Subduction at deep-ocean trenches**===
 * ocean floor gets wider caused by sea-floor spreading
 * deep ocean trenches allows subduction to take place


 * ===**Subduction and Earth's Oceans**===
 * ocean floor completely changes outcome every 200 million years.
 * old rocks move across oceans to sink into trenches.


 * ===**Subduction in the Pacific Ocean**===
 * Pacific Ocean has many trenches, so the trenches swallow the Pacific Ocean parts, and the ridge is not adding new ridges fast enough.

Subduction in the Atlantic Ocean

 * Atlantic Ocean is expanding because it has very few trenches
 * the spreading ocean floor has nowhere to go, so it just goes everywhere
 * the Atlantic Ocean is also sort of dragging the edges of the continents

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