Download Ocean floor Notes: Sea Floor Spreading I. Sea Floor Spreading

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Notes: Sea Floor Spreading
I.
Sea Floor Spreading
 Supports the Theory of Continental Drift
II.
Mid-Ocean Ridges
 Long chain of underwater mountains
 Rift valley runs through most of the center
Lava hardens &
forms new floor
Ocean Floor
Ocean Floor
Ocean floor
Magma
III.
Formation of new ocean floor
 Molten material rises from mantle & erupts
 Molten material spreads out – pushing older rock aside
 Molten rock cools forming a strip of solid rock in the
center
 More molten material then splits apart the strip formed
before, pushing it aside
IV.
Other supporting evidence
 “pillow” rock: rock formed from quick cooled molten
material
 Magnetized “stripes”: pattern on both sides of ridge is
the same
 A record of magnetic field reversals on Earth
 Rock samples: oldest rocks are formed farthest from
ridge
IT’S NOT JUST SPREADING. IT’S SINKING!
Trench
V.
Subduction
 Process by which old ocean floor sinks beneath a deepocean trench and back into mantle
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