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Who was Alfred Wegener?. Alfred Wegener was a young German scientist who in 1910 proposed that the continents moved. What was Wegener’s hypothesis?. What was Wegener’s hypothesis?.

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who was alfred wegener
Who was Alfred Wegener?
  • Alfred Wegener was a young German scientist whoin 1910 proposed that the continents moved.
  • What was Wegener’s hypothesis?
what was wegener s hypothesis
What was Wegener’s hypothesis?
  • Continental Drift: all continents were once joined together in a single landmass and have since drifted apart.
  • What evidence did Wegener have?

Pangea means “All lands.”

what evidence did he have
What evidence did he have?
  • Wegener gathered evidence from different scientific fields to support his ideas about continental drift.
  • Wegener studied land features, fossils, and evidence of climate change.

Please turn to page 138 -139 of your textbook.

drifting continents
Drifting Continents
  • Wegener’s idea of a supercontinent was not accepted by the world because he could not provide a satisfactory explanation for the force that pushes or pulls the continents.
  • What force do you think moves the continents?

http://www.livescience.com/images/pangea_animation_03.gif

who is arthur holmes
Who is Arthur Holmes?
  • Around 1930, Arthur Holmes suggested the power of convection.
  • Currents of heat and thermal expansion in the Earth's mantle, he suggested, could force the continents toward or away from one another, creating new ocean floor and building mountain ranges.
  • He warned that his ideas were "purely speculative" and could "have no scientific value until they acquire support from independent evidence."
what is convection
What is Convection?
  • Convection is the movement of molecules within fluids.
  • Movement is caused by differences of temperature and density within a fluid.
slide7
1. As a liquid is heated, the particles move faster and spread apart.
  • 2. As a result, the particles of a heated fluid occupy more space.
  • 3. The fluid’s density decreases.
  • THE HOTTER (less dense) LIQUID MOVES UP.
  • 4. But when a fluid cools, its particles move more slowly and settle together more closely.
  • 5. As the fluid becomes cooler, its density increases.
  • THE COOLER (more dense) LIQUID SINKS DOWN.

Heat Rises!

so what possible force can there be that might push or pull the continents
So… what possible force can there be that might push or pull the continents?

http://www.geoham.net/6/fys/tekton/recon.gif

what force moves the continents
What force moves the continents?
  • Heat from the core and the mantle cause convection currents in the mantle.
  • These currents are believed to be what moves the plates.
  • Although Holmes had an explanation, he could provide no evidence.