2 - Continental Drift
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Transcript of 2 - Continental Drift
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MOVING CONTINENTSTheory of Continental Drift
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Alfred Wegener
-German Meteorologist
-Jigsaw Puzzle effect
-Fossil Evidence
-Centrifugal Force
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Continental Drift Theory
Alfred Wegener (1880 - 1930)
German meteorologist suggested in 1912 that
continents have moved slowly to their currentpositions
PANGAEA 250 m.y.a. all continents wereonce connected as one large land mass
GONDWANA &LAURASIA- 180 - 200 m.y.a.land mass broke apart, and the Earthscontinents began drifting to present locations
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PANGAEA
GONDWANA
&
LAURASIA
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ContinentalDrift
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History of Continental Drift Theory
Thoughts about continental drift had beenaround for a very long time
Sir Francis Bacon in the early 1600s hadwritten about it
Most based theory on deduction and small
pieces of evidence Wegner gathered a larger and more
complete body of evidence
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Evidence for Continental Drift
JIG SAW PUZZLE-likefit of the continents
FOSSILSsimilar fossils on different
continents
Glossopteris - ferns
Lystrosaurusreptile fossils found in S. Africa,
Antarctica, India, China
Warm weather plant fossils found in Arcticregions
GLACIAL DEPOSITSfound in areas
presently in the tropics
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Fossil Evidence
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GlacialEvidence
Grooves carved by glaciers (shown by arrows)
provided evidence for continental drift.
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More Evidence
Similar rock structures on different
continents
COAL BEDS
MOUNTAIN RANGES
rocks on the east coast of S. America match those
on the west coast of Africa, tests reveal they
formed at the same time (550 mya)
belt of mountains along the east coast of N.
America match those existing in northern Europe
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MOUNTAIN RANGES
Explanation for their existence
Cooling, Contracting-Earth Theory
they formed on the Earth's crust as wrinkles form
on the skin of a drying apple. If this were so,however, they should be spread evenly over the
Earth; instead mountain ranges occur in narrow
bands, usually at the edge of a continent.
Continental Drift (WEGENER) Mountains formed when the edge of a drifting
continent crumpled and foldedas when India hit
Asia and formed the Himalayas.
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Similar Layers of Rock
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Mountain Chains
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No Support for Continental Drift?
Flaws with theory at the time:
Earths crust was believed to be too rigid;
No suitable mechanism to provide enough
energy to move the continents such great
distances could be identifiedEarth does
not spin fast enough!
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Continental Drift NOT Accepted
NOT accepted because how or why
continents had moved could not be
explained!!
Wegner tried to base movement of continents ongravitational pull and centrifugal force!
The fact that Wegner was a meteorologist ledsome people to not believe his thoughts ongeologyparticularly when he could not provideevidence to support his hypothesis.
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Why wasnt the Theory of
Continental Drift Accepted?
METEOROLOGIST vs. GEOLOGIST
DRIVING FORCE =
CENTRIFUGAL FORCE OF THE EARTH.
(Not believed to be strong enough.)
http://earthobservatory.nasa.gov/Features/Wegener/wegener.php
Nice biography of Alfred Wegener
http://earthobservatory.nasa.gov/Features/Wegener/wegener.phphttp://earthobservatory.nasa.gov/Features/Wegener/wegener.php
