jan 2510:07 am - grafton school district
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(Greek philosopher)
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were once joined together
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1750 GeorgesLouis Leclerc (Compte de Buffon) French Naturalist
were very similar = Connected land masses
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(French Geographer)
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1880's Edward Suess (English Geologist)
Nearly identical geologic record of southern continents Proposed all southern continents were connected in a super
continent called Gondwana
Major Problems: Continents were constant! How could something as large as a continent be moved?
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(American Geologist)
Proposed continents move over time! Proof: Mountain ranges along the edges of continents were the
results of large collisions How? Moon causes tides and pulls continents
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(American Geologist)
Combined Edward Suess idea of connected continents with
Continents were connected and drifted apart over time Problem: could not explain how
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(German Meteorologist)
Grandfather of modern plate tectonics Proposed all land masses were once connected in a land mass called Pangea
Called drifting continents: Continental Drift
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1. Puzzle fit of continents
3. Rock records also matched Driving Force: Rotation of planet spread out the continents
His ideas were rejected during his lifetime
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1950's evidence for Wegner's ideas started to pile up
b. deep sea trenches
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2. Rock Magnetism Basalt has lots of iron in it. Iron pieces point towards the North Pole like compasses
when magnetic pole reverses it record the change in the rock Identical pattern on both sides of the midocean ridge
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3. Seismology imaging of the inside of the earth using wave energy better understanding of the inside of the earth
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1960's sea floor spreading theory midocean ridge pushes continents apart
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1968 William Jason Morgan (American Geophysicist) Proposed the earth was covered by 12 large land chunks called Plates
rock inside the earth
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Hot Cold
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2. Slab Pull: as plates are recycled in the Earth they dive
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3. Ridge Push: where the plates are lifted along the midocean ridge, gravity pulls them down causing them to spread
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Plate Boundaries
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1. Convergent: where two plates hit each other
a. Continent / Continent collision = mountains (earthquakes)
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b. Continent / Ocean collision = subduction zone (volcanoes + earthquakes)
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2. Divergent: where two plates pull apart = midocean ridge
Earthquakes)
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slide past each other (earthquakes)