Transcript Wegener`s Theory of Continental Drift

Wegener’s Theory of Continental
Drift
Beth Roland
Eighth Grade Science
Team 5 Mountaineers
Background of Wegener
A German (1880-1930)who completed
A Doctorate degree in Astronomy
developed the theory of Continental Drift.
His theory hypothesized that the
continents were slowly drifting
around the Earth.
As he had no way of explaining
how the continents moved, he theory
was mostly dismissed.
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Pangaea
Pangaea Overview
 Pangaea- “all earth” the supercontinent that
existed during the Paleozoic and Mesozoic
eras about 250 million years ago, before the
continents were separated into their current
configuration.
 Panthalassa- “all sea” global ocean that
surrounded the supercontinent Pangaea
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180 MYA- Pangaea Splits
Based on Wegener’s
Reasearch, pangaea split
Into 2 sub-continents;
Laurasia (northern hemisphere)
and Gondwana (southern
Hemisphere)
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65 MYA- subcontinents continue to
subdivide
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Based on plate tectonic research, the image shows
the approximate continent configuration that occurs
as dinosaurs were becoming extinct
Sea Floor Spreading
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Throughout all of the Earth’s oceans we find mid-ocean
ridges that cause the sea floor to spread outwards of the
underwater mountain chains.
As oceanic plates diverge away from each other, they
create a separation or gap. This gap is quickly filled by
magma rising from the Asthenosphere into the Lithosphere
that contains the Earth’s crust.
Magnetic Polarity of Earth
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One major piece of evidence supporting sea floor
spreading (further evidence of Wegener’s hypothesis)
is the magnetic “fossilized minerals”; trapped in
sections of the sea floor that occur around mid-ocean
ridges.
The Earth at certain intervals, has changed polarity.
The magnetic minerals trapped in these sections are
frozen in time and are aligned based on the magnetic
polarity of the earth at the time.
This record of magnetic reversals is the final proof that
sea-floor spreading occurs.
Magnetic Reversals and Sea Floor
Spreading