Theory of Theory of Continental DriftContinental Drift

James Hutton 1785 James Hutton 1785 UniformitarianismUniformitarianism

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UniformitarianismUniformitarianism

The present is the key to the pastThe present is the key to the past The geological forces and processes The geological forces and processes

of today are the same as those from of today are the same as those from the past.the past.

These forces are very slow and These forces are very slow and methodical.methodical.

Alfred Wegener 1915 Alfred Wegener 1915 Continental DriftContinental Drift

Recurring patterns on Recurring patterns on continentscontinents

Evidence for continental Evidence for continental driftdrift

Matching Coastlines(jigsaw puzzle)

Evidence for continental Evidence for continental driftdrift

Matchingfolded mountainRanges(Atlas, Appalachians, and Scandinavian Highlands)

Evidence for continental Evidence for continental driftdrift

Matching glacierdeposits

Evidence for continental Evidence for continental driftdrift

MatchingFossils(Lystrosaurus)

Evidence for continental Evidence for continental driftdrift

Matching coastlinesMatching coastlines Matching folded mountainsMatching folded mountains Matching glacier depositsMatching glacier deposits Matching fossilsMatching fossils

PangaeaPangaea

A Greek word meaning “All-lands” A Greek word meaning “All-lands” Split apart approximately 200 MYBPSplit apart approximately 200 MYBP

1915 maps by Wegener 1915 maps by Wegener of Pangaeaof Pangaea

Continental driftContinental drift

Theory that continents drift on the Theory that continents drift on the surface of the Earthsurface of the Earth

No mechanism proposedNo mechanism proposed No one believed this was possibleNo one believed this was possible Do you think continents can float ?Do you think continents can float ?

Glomar ChallengerGlomar Challenger

1960’s this ship took core samples of 1960’s this ship took core samples of ocean floor rocks as it crossed the ocean floor rocks as it crossed the Atlantic OceanAtlantic Ocean

A map was produced from this data A map was produced from this data showing the rock types and agesshowing the rock types and ages

From this map a new theory was From this map a new theory was developed to explain Wegener’s developed to explain Wegener’s evidenceevidence

Ocean floor rock agesOcean floor rock ages

Get older symmetrically away from Get older symmetrically away from ridges, the oldest rocks have to be ridges, the oldest rocks have to be 200,000,000 years old200,000,000 years old

Theory: sea floor splits apart and Theory: sea floor splits apart and rocks move away from each otherrocks move away from each other

Process: Seafloor spreadingProcess: Seafloor spreading Seafloor spreading provides clues to Seafloor spreading provides clues to

mechanism driving continental driftmechanism driving continental drift

Topography of ocean Topography of ocean floorfloor

Does sea floor spreading explain Does sea floor spreading explain everything ?everything ?

If the Atlantic Ocean is spreading, If the Atlantic Ocean is spreading, doesn’t that mean some place is doesn’t that mean some place is being squeezed togetherbeing squeezed together

Recurring patterns in Recurring patterns in oceansoceans

Plate TectonicsPlate Tectonics

Combining Wegener’s evidence, Combining Wegener’s evidence, Glomar Challenger’s data, and the Glomar Challenger’s data, and the following world map the present following world map the present theory of Plate Tectonics came into theory of Plate Tectonics came into beingbeing

Earthquake and Volcano Distribution