Plate Tectonics and Earth's Movement

Plate Movement

What is Plate Movement?

• The movement of the Earth's lithosphere, which is the outermost solid layer of the planet
• The lithosphere is broken into several large plates that fit together like a jigsaw puzzle

Types of Plate Movement

• Divergent Motion: plates moving apart from each other
  • New crust is formed as magma rises to fill the gap
  • Examples: Mid-Ocean Ridges, East African Rift System
• Convergent Motion: plates moving towards each other
  • Can result in subduction (one plate is pushed beneath another) or collision (plates collide and crumple)
  • Examples: Andean mountain building, Himalayan orogeny
• Transform Motion: plates sliding past each other horizontally
  • No creation or destruction of crust
  • Examples: San Andreas Fault, North Anatolian Fault

Factors Affecting Plate Movement

• Convection Currents: slow circulation of hot, viscous rock in the Earth's mantle
  • Drives plate movement by exerting forces on the base of the lithosphere
• Ridge Push: force exerted by the creation of new crust at mid-ocean ridges
  • Pushes plates apart and drives divergent motion
• Slab Pull: force exerted by the sinking of dense, cold plate material into the mantle
  • Pulls plates towards each other and drives convergent motion

Evidence for Plate Movement

• Fit of the Continents: the shape and fit of the continents, particularly Africa and South America
• Mid-Ocean Ridges: vast underwater mountain ranges formed by plate divergence
• Paleomagnetism: the study of the Earth's magnetic field as recorded in rocks
  • Shows that the Earth's magnetic poles have reversed over time, and that the rocks have moved over time