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Introduction to plate tectonics

NGSS.MS:
MS‑ESS2‑2
,
MS‑ESS2‑3
,
MS‑ESS2.A.2
,
MS‑ESS2.B.1
Review your understanding of plate tectonics in this free article aligned to NGSS standards.

Key points:

  • Earth’s lithosphere, or outermost shell, is broken up into large pieces called tectonic plates.
  • These plates move slowly over the asthenosphere, a layer of softer rock below the lithosphere. On average, tectonic plates move a few centimeters per year.
  • The place where two plates meet is called a plate boundary. There are three main types of plate boundaries.
    • Divergent boundaries occur where two plates are moving away from each other. Along these boundaries, rift valleys and mid-ocean ridges are common.
    • Convergent boundaries occur where two plates are moving toward each other. Along these boundaries, mountains and trenches are common.
    • Transform boundaries occur where two plates are moving past each other. Along these boundaries, earthquakes are common.
  • Evidence for plate motion can be seen in various features on Earth. For example, some of the continents have complementary coastlines. This suggests that the continents were once joined together.
Earth’s major and minor tectonic plates.
A map showing the boundaries of Earth’s major and minor tectonic plates. Image credit: U.S. Geological Survey on Wikimedia Commons, public domain.

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