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What is plate tectonics?

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Quick answer

Plate tectonics is the theory that Earth's rigid outer shell is broken into large plates that slowly move on the hotter, softer mantle beneath. Their motion builds mountains, opens oceans, and causes most earthquakes and volcanoes. Earth's lithosphere is split into about a dozen major plates.

Key things to understand

  1. Earth's lithosphere is split into about a dozen major plates.
  2. They move a few centimeters a year, driven by heat-driven motion in the mantle.
  3. Plates pull apart (making new crust), collide (building mountains), or grind past each other.
  4. Most earthquakes and volcanoes occur along plate boundaries.

People also ask

What causes earthquakes?
Stress building up as plates grind past or against each other, released suddenly when the rock slips.
How fast do tectonic plates move?
Roughly 2–10 cm per year — about as fast as your fingernails grow.
What is the Ring of Fire?
A horseshoe-shaped zone around the Pacific where many plate boundaries meet, producing frequent earthquakes and volcanoes.

Part of the guide: Nature & Earth: Living Things and Rocks →