The Theory of Sea Floor Spreading

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Sea Floor Spreading

• Harry Hess (1960)

• as the ocean floor spreads apart, new crust material rises from the mantle and creates new sea floor to fill the “hole.”

HESS (1960)• Sea floor spreading • Continents were moving (as Wegener had proposed)• Evidence1.2.3.

1. The discovery of the Mid-ocean Ridge

• Scientists mapped 47,000 miles of underwater volcanic ridges by using sonar

Map of Mid-ocean Ridges

2. Ocean floor shows Magnetic Poles reversing

3. Ocean floor samples—older crust is further away from ridges