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Seafloor Spreading

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Katherine Tran

on 15 October 2015

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Transcript of Seafloor Spreading

Seafloor Spreading
designed by Péter Puklus for Prezi
Investigating the Seafloor
Wegener collected most of his evidence at Earth's surface.
New technology allowed scientists to collect rock samples and map out the seafloor.
Sonar emitted sound waves from boats. Waves would bounce back and the receiver recorded the time it took for waves to return.
They used speed of sound to calculate the depth of the water.
Mid-Ocean Ridges
Hidden under ocean waters are long mountain ranges called
mid-ocean ridges
.
Scientists studied temperatures on the seafloor and learned that there was more heat escaping at mid-ocean ridges than any other location in the oceans.
Harry Hess proposed that lava erupted at mid-ocean ridges and made new seafloor.
Seafloor spreading
is the process by which new seafloor is continuously made at mid-ocean ridges
Magma rises to the surface through convection and flows out as lava.
When the lava dries, it turns into new seafloor.
Evidence for Spreading
A compass points to Earth's magnetic north pole
today
. This is called
normal
.
In past times, your compass might have pointed to Earth's magnetic south pole. This is called
reversed
.
Recording these reversals allowed scientists to measure the magnetic stripes on the seafloor to determine a rock's age, thus calculating the speed of seafloor movement.
Scientists finally understood how continents could move and Wegener's continental drift hypothesis was accepted.
Seafloor Drilling
In 1968, a boat named the
Glomar Challenge
drilled into the seafloor and collected samples with a diamond-tipped drill.
These samples showed that the oldest rocks were farthest from the mid-ocean ridge.
This supported the seafloor spreading hypothesis.
Bill Nye on Seafloor Spreading
Full transcript