A mountain chain is a series of mountains that are geologically linked together. Such mountains have some similarities between them such as age, form, and size. A mountain chain stretches mostly across continents or countries and is often used to mark boundaries. Mountain chains are formed through a process called plate tectonics. Plates are fragments of the Earth’s crust, and when they collide, they buckle and force vast areas of land to rise. This is the reason why most of the mountains found in chains are Fold Mountains. The Andes in South America is the longest mountain range in the world. A mountain range or a mountain chain is a series of geologically linked mountains. These mountains are similar in age, form, and size.