If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content

Plate tectonics and the ocean floor

NGSS.MS:
MS‑ESS1.C.2
,
MS‑ESS2‑2
,
MS‑ESS2‑3
,
MS‑ESS2.A.2
,
MS‑ESS2.B.1
Review your understanding of plate tectonics and the ocean floor in this free article aligned to NGSS standards.

Key points:

  • There are two types of tectonic plates: oceanic and continental. Oceanic plates make up the ocean floor. Continental plates make up the continents.
  • Both oceanic and continental plates are topped by crust. On average, oceanic crust is denser than continental crust.
  • A trench forms when an oceanic plate collides with another plate at a convergent boundary. When this happens, the denser plate is subducted, or pushed under, the less dense plate.
  • A mid-ocean ridge forms when two oceanic plates move apart at a divergent boundary.
  • New oceanic crust is created at mid-ocean ridges. As it ages, it moves away from the ridge and becomes cooler and denser. Eventually, the crust reaches a trench and is destroyed.
The Mid-Atlantic ridge.
A false color map of the Mid-Atlantic Ridge. The ridge is shown in light blue in the middle of the Atlantic Ocean. Image credit: NOAA on Wikimedia Commons, public domain.

Want to join the conversation?