sea floor spreading inside earth ch. 1.4. introduction a. deep in the ocean the temp is near...
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Sea Floor Spreading
Inside EarthCh. 1.4
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Introduction
A. Deep in the ocean the temp is near _freezing_(0C)
B. Many things live in the deep ocean.
1. Giant __tubeworms_ and clams
2. Provide evidence for Wegener’s hypothesis of __Continental Drift__.
500 × 340 - nsf.gov
500 × 340 - nsf.gov
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I. Mid Ocean Ridges
A. Sonar = device that bounces sound waves off underwater objects and records them
B. Mid-ocean ridges are _mountain chains underwater and the island of Iceland.
C. Mapping the ridges makes scientists want to know more about them.
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II. What is Sea Floor Spreading
A. _Harry Hess_ an American geologist studied mid-ocean ridges.
B. His idea was of sea-floor spreading that continually adds new __material___ to the __ocean floor.
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Sea Floor
C. Sea floor spreads apart along both sides of mid-ocean ridge as __new crust is added.
D. As the ocean floor moves, the _continents_ move too.
E. _Older_ rock gets pushed further out from the ridge.
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Sea Floor
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III. Evidence from Sea Floor Spreading
A. Molten Material
1. A submarine, Alvin went to the ocean floor to find evidence of sea-__floor__ _spreading__. Molten material is erupting from the mantle and hardens quickly when it hits the cold ocean water.
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Evidence
B. Magnetic stripes
1. Scientists found that the rock makes up the ocean floor lies in patterns of _magnetized__ “stripes”.
2.These stripes hold a record of __reversal___ in Earth’s magnetic field.
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Evidence
C. Drilling samples
1. Drilling into oceanic rock has given us the _ages_ of the rock.
2. Scientists determined that the _youngest__ rocks were __closest__ to the center of the mid-ocean ridges and the older rocks were farther away from the ridges.
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IV. Subduction at the Trenches
A. deep ocean trenches = underwater canyon
B. Subduction = ocean floor moves back into the mantle through deep ocean trenches
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Subduction
C. Subduction and Earth’s oceans
1. Pacific Ocean is __Shrinking__;
2. Atlantic Ocean is _Expanding___.