Final answer:
The process of the earth's crust wrinkling when land masses collide is known as folding, and is a key factor in mountain range formation such as the Alps.
Step-by-step explanation:
When the edges of land masses rub or bump into each other, causing the crust to wrinkle, geologists refer to this process as folding. This occurs particularly when two continental masses are on a collision course, exerting great pressure against each other.
This is how many mountain ranges, including the Alps, are formed, with the earth buckling and creating folds that can raise portions of the crust to great heights.
Another important geologic process at plate boundaries is subduction, where one plate is forced beneath another into the mantle, resulting in features like ocean trenches and playing an integral role in recycling the earth's crust.