How old are crustal rocks

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The friction between the plates prevents the subducting oceanic plate from sliding. As it descends, it drags against the overlying plate, causing both to fracture and deform. This causes frequent earthquakes that get deeper as the ocean plate descends further.”The effect of the collision of the two plates deforms the leading edge of the South American Plate by folding the rocks. This crustal shortening increases the vertical thickness whilst reducing the width of the lithosphere in the collision zone (imagine a car hitting a solid wall) and so produces the fold mountains of the Andes.”When the subduction continues the plate brings sea water, locked in the ocean crust, deep into the mantle. As the plate heats up the water is liberated, lowering the melting point of the mantle and causing partial melting. This produces magma, which rises and may be erupted explosively. I. K., & P. L. (2016)

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