As a geologist with expertise in structural geology, I can explain the types of stress that lead to folding. Folding is a structural feature that results from the deformation of the Earth's crust due to various types of stress. The most common type of stress that causes folding is compressional stress. This stress occurs when rocks are subjected to forces that push them towards each other, causing the layers to buckle and fold. Compressional stress can be caused by the movement of tectonic plates, where the collision or convergence of these massive slabs of the Earth's lithosphere results in the shortening and thickening of the crust. This process can lead to the formation of mountain ranges, such as the Himalayas, which are the result of the ongoing collision between the Indian and Eurasian plates. In addition to compressional stress, there are other types of stress that can cause deformation in rocks, such as tensional stress, which pulls rocks apart, and shear stress, which causes rocks to slide past one another. However, these are less likely to result in the formation of folds compared to compressional stress. To summarize, the primary cause of most folding is compressional stress, which is often a result of tectonic plate interactions. read more >>

A bend in a set of rocks caused by compression. Folds are easiest to see in sedimentary or volcanic rocks that were deposited horizontally. The block of rock that is beneath a dip-slip fault. A break in rock caused by stresses along which there is no movement.read more >>