Are Fold Mountains formed as a result of volcanic or earthquake tectonic activity?
Neither, really. Earthquakes imply a break in the crust, which in purely fold orogeny hasn’t happened. However, it’s definitely not volcanism. If you only have those two options, go with earthquake. In truth, fold orogeny (mountain building) happens through compression, forcing acting against and toward each other, strong enough to deform rock. However, either the compression isn’t strong enough, or the rock is ductile enough that instead of fracturing and creating a fault, it simply folds and makes pretty bends. The cliche example is to take a long runner of carpet and take your self and a friend on either end and push toward each other. The carpet will bunch in the middle in folds, without fracturing, and obviously without a volcano going off. When layers of rock are pushed inwards from both ends, they crumple up into waves. Rocks are too hard to be squashed into a smaller space (to become denser). Instead they fold upwards and downwards. The immense forces that cause folding can cru
