Continental drift

-Continents drift is a theory made by Alfred Wegner.  

-Proof: 

  • There are similarities in shape on the continents. (South America and Africa)

  • Fossil evidence. (Mesosaurus) 

  • Evidence from Ice sheets, glaciers. Marks are left from preexisting ice sheets.

  • Location of coal beds. Can mostly be found in Swampy areas. 

  • Rock type and Structural similarities. 

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  • Convections- hot magma rises up and then sinks down, dragging the lithosphere plate with it. Is the driving force of plate boundaries. 

  • Gravity driven ridge push- the ridges push and pull. ---------->

  • Gravity driven slab pull- the plates subduct gravity pulls it down.

  • Come together- convergent

  • Move apart- Divergent 

  • Slide past one another– transform

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  • Convergent boundaries- plates move together and can create volcanic mountain ranges, and folded mountains. (ocean and continental) 

  • When oceanic plates collide with continental the thinner and denser plate subducts. (Volcanic mountain)

  • When 2 oceanic plates collide the older, cooler denser plate will subduct. (volcanic island arc) 

  • When 2 continental form together the crust is folded and faulted. (collision boundary and folded mountains) 

  • Transform boundary- plates slide past each other.  

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Evidence today- 

  • Age of rocks on ocean plates are older as you move away from the ocean ridge. Shows that ridges are where ocean floors form.

  • Heat flow measurement along the ridge shows the new crust is being formed. As distance increases the temperature decreases. 

  • Studying magnetic polarity of the ocean floor. The magnet field tries to align itself and the moving of magnetic field shows the movement of plates..