Final answer:
Mountain chains, such as the Alps, are formed when two continental plates collide. One piece of evidence for this theory is the occurrence of periodic earthquakes in the region.
Step-by-step explanation:
Mountain chains, such as the Alps, are formed when two continental plates collide. When this happens, the plates push against each other under great pressure, causing the Earth's crust to buckle and fold. As a result, some rocks are dragged deep below the surface, while others are raised to form mountains. This is how the Alps were formed, with the African plate colliding with the Eurasian plate. One piece of evidence for this theory is the occurrence of periodic earthquakes in the region.