Question

how was mountain formed

Answer 1

movement of tectonic plates create volcanoes along the plate boundaries, which erupt and form mountain.
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Answer 2

Movements of tectonic plates create volcanoes along the plate boundaries, which erupt and form mountains. A volcanic arc system is a series of volcanoes that form near a subduction zone where the crust of a sinking oceanic plate melts and drags water down with the subducting crust.

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