I have a very basic doubt regarding what the tectonic plates mean. In Wiki article Subduction is defined as:

Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries.

and when I follow the link to convergent boundary it is defined as:

A convergent boundary (also known as a destructive boundary) is an area on Earth where two or more lithospheric plates collide.

Now from what I know is that the tectonic plates comprise of oceanic and continental crust and convergent and divergent boundaries exist where two tectonic plates meet. So this subduction should only happen where two or more major or minor plates meet and not between continental crust and oceanic crust. So do plates sometime refer to crust as well and there are more minor and major plates which are still not defined.

Edit: Is there a possibility of subduction between continental crust and oceanic crust of the same plate?(If answer is yes then these crusts can also be called plates).

  • $\begingroup$ I'm not understanding what you are now asking, or perhaps you aren't understanding plate tectonics. While there are a few places where the plate boundaries aren't quite clear, the basic idea of plate tectonics is that every square centimeter of the Earth's solid surface, whether it be oceanic or continental crust, is a small part of exactly one tectonic plate. You appear to be thinking that plate tectonics is something else. $\endgroup$ Oct 8, 2021 at 5:15
  • $\begingroup$ @DavidHammen ok got it; so there is no possibility of subduction in the same plate. $\endgroup$ Oct 8, 2021 at 6:10
  • $\begingroup$ for the edit if they are on the same plate then they are not a boundary, a boundary is a contact point between two plates. $\endgroup$
    – John
    Oct 12, 2021 at 20:50
  • $\begingroup$ @DavidHammen you couldn't be more wrong about that. Plate boundaries are often not always well defined, or depend on scale or interpretation, and may comprise many plates which are only considered a single plate on a different scale. this is especially true of transform boundaries. Then you have cratons which are ancient plates now fused to other plates, California could contain on two plates or hundreds depending on your scale. $\endgroup$
    – John
    Oct 12, 2021 at 20:57

1 Answer 1


Tectonic plates almost all comprise a mix of both oceanic and continental crust in different areas. The exceptions are all minor plates.

  • Where the edges of these plates spread apart you get divergent boundaries. These are always found in a single rock type; in continental crust these are the rift valleys while at oceanic boundaries they are the mid-ocean ridges.

  • Where the edges come together you get convergent boundaries, these almost always involve subduction of denser plate material under lighter rock. The density split is often defined by rock type with dense basaltic oceanic crust being pushed under lighter continental rock along deep ocean trenches but there are several places where older, cooler oceanic rock subducts below younger, hotter oceanic crust.

  • Where two continental plate boundaries collide neither can subduct because they are so much less dense than the underlying mantle so you get massive mountain ranges like the Himalaya. The Atlas, Alps, and Pyrennes are at the beginning of the process as Africa slowly closes the Mediterranean and crashes into Europe.

  • $\begingroup$ So these plates can also slide across or they just pull(divergent) and push(convergent)? $\endgroup$ Oct 7, 2021 at 7:35
  • 1
    $\begingroup$ @dark_prince The can also slide across one another. These are called transform boundaries or slip-strike boundaries. The San Andreas Fault in California is an example. $\endgroup$ Oct 7, 2021 at 11:44
  • $\begingroup$ @DavidHammen thanks; please edited question. I think my question wasn't clear enough. $\endgroup$ Oct 7, 2021 at 13:42

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