Sea Floor spreading

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Sea Floor spreading
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A hypothesis was presented in 1963 by Fred Vine
and Drummond Matthews to explain this pattern.
They proposed that lava erupted at different
times along the rift at the crest of the
mid-ocean ridges preserved different magnetic
anomalies.
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Vine and Matthews proposed that lava erupted on
the sea floor on both sides of the rift,
solidified, and moved away before more lava was
erupted. If the Earth's magnetic field had
reversed (changed from one geographic pole to the
other) between the two eruptions, the lava flows
would preserve a set of parallel bands with
different magnetic properties.
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Magnetic Stripes

•   After the Second World War geologists had the
  technology to study the sea floor.
•  They used ships and planes with magnetometers to
  measure the magnetic field above the ocean floor.
•  During the history of the Earth the direction of
  magnetic north has frequently changed/reversed.
•  Thus sometimes rocks are magnetised to the North
  and sometimes to the South.

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Magnetic Stripes

•  It was found that rocks could be mapped as
  magnetic stripes parallel to the M.O.R. with
  alternating North and South magnetised rocks.
• These stripes were the same on either side of the
  M.O.R. i.e. they were mirror images.
• The rocks also got older as you moved away from
  the ridge.

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New Evidence 4

• Emergence of the seafloor-spreading hypothesis
  and associated recycling of oceanic crust and

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New Evidence 5

• Precise documentation that the world's earthquake
  and volcanic activity is concentrated along
  oceanic trenches and submarine mountain ranges.

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New Evidence 2

• In particular, four major scientific developments
  spurred the formulation of the plate-tectonics
  theory
• Demonstration of the ruggedness and youth of the
  ocean floor

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New Evidence 3

• confirmation of repeated reversals of the Earth
  magnetic field in the geologic past

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The Mariana Trench is 1,554 miles long and 44
miles wide. The Challenger Deep is the deepest
point on Earth. a depth of nearly 7 miles.
In 1960, the Trieste, a manned submersible owned
by the U.S. Navy, descended to the bottom of the
Mariana Trench. There, the pressure from the
weight of the vast ocean above is tremendous. At
more than 8 tons per square inch, its the
equivalent of one person trying to hold 50 jumbo
jets!
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The emergence of sea-floor
spreading?

• Magnetic stripes Vine Mathewss hypothesis

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Late 1960s and the emergence of plate tectonics

• Computer-assisted continental fits (Bullard,
  Everett and Smith)
• The distribution of seismicity and the
  recognition of plate boundaries

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Plate Tectonics
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