Why are subduction zones not formed at continental-continental
convergent boundaries?

Subduction zones are collision between two tectonics plates such that one of the plates is subducted to the mantle (or sinks) directly below the other plate

Whereby the densities of the convergent (colliding) continental plates are lower than the density of the mantle, subduction is prevented from occurring, and subduction zones are not formed at the continental-continental convergent boundaries

Explanation:

b. niger

explanation:

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