What are fold mountains?
Fold, in geology, bend in a rock layer caused by forces within the crust of the earth. The forces that cause folds range from slight differences in pressure in the earth’s crust, to large collisions of the crust’s tectonic plates. As a result, a fold may be only a few centimeters in width, or it may cover several kilometers. Rock layers can also break in response to these forces, in which case a fault occurs. Folds usually occur in a series and look like waves. If the rocks have not been turned upside down, then the crests of the waves are called anticlines and the troughs are called synclines. Collisions between plates of the earth’s crust trigger various geologic processes that result in crustal uplift. A common process, produced by horizontal compression, is the deformation of crustal strata into folds or wrinkles or the thrusting of vast, thick sheets of rock over one another. The Himalayas, for example, were raised by the compression that accompanied collision of the Indian plate
