A collision that crumples the crust
Continental crust is buoyant and relatively difficult to sink into Earth’s mantle. When two continental plates converge, neither easily slides beneath the other. Instead, the immense pressure compresses the crust: layers of rock fold, crack, and ride over neighboring layers along faults. This shortening can stack rock upward and thicken the crust, much as pushing a rug across a floor makes it bunch into ridges.
Mountains rise as the crust thickens
The thickened crust is also pushed deeper into Earth, where heat and pressure can alter the rock. Its deep “root” helps support the high terrain above, while continued plate movement can keep adding pressure and lifting parts of the range. The Himalaya, formed as the Indian and Eurasian plates converged, is a familiar example of this ongoing process.
A mountain’s height is not simply the total amount of rock pushed upward. Rivers, glaciers, and weather wear the range down at the same time. A mountain range grows when tectonic uplift outpaces that erosion—and its shape records the balance between the two forces.
