Plate tectonics

G3 Elective Geography: Tectonics - syllabus K335, 2027

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Why plates move, how we know, and how landscapes form.

• Earth's layers and tectonic plates

  A tectonic plate is a moving piece of lithosphere: the crust and the rigid uppermost mantle.

• Why tectonic plates move

  Slow mantle circulation and the pull of sinking oceanic slabs help move tectonic plates.

• Seafloor spreading evidence

  New crust forms at a mid-ocean ridge and moves away. Rocks on both sides therefore become older with distance from the ridge.

• Magnetic striping

  Cooling basalt records Earth's magnetic field. Matching bands on opposite sides of a ridge support seafloor spreading.

• Plate boundaries

  Plate movement and plate type determine what happens at a boundary: new crust, subduction, mountains or sideways fault movement.