Plate Boundary: Divergent (Fast-spreading Ridge)

How do mid-ocean ridges form new crust?

Spreading mid-ocean ridges form the longest mountain ranges in the world. New oceanic crust is created at this boundary when basalt magma, formed in the mantle, rises into fractures in the crust and solidifies. Spreading ridges are high elevation because the young oceanic plate at the ridge crest is hot and less dense than the older, colder and more dense plate on the flanks of the ridge. As the plates move away from the boundary, they thicken because underlying mantle rocks cool and add to the bottom of the plate.


Keypoints:

  • Hot mantle rock rises beneath mid-ocean ridges
  • Melt forms beneath the lithosphere
  • Magma rises into magma chambers
  • Lava erupts onto ocean floor building new crust
  • Plates move apart

Total Time: 1min 10s
Level: Novice

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