Many Alpine ranges consist chiefly of limestone that also formed in the seabed. Most of the Alps had taken shape by about 15 million years ago. Glaciers occupied valleys high in the Alps from about 2 million years ago until about 10,000 years ago. As these glaciers moved downhill, they gouged the earth and rock, creating U-shaped valleys. Other geologic features visible in the Alps include cirques and cols.
Cirques are bowl-shaped hollows near the peak of a mountain.
A col is a high pass between two cirques. A hanging valley is a small valley that empties into a larger and lower valley. A stream flowing through a hanging valley may create a waterfall. The Alpine glaciers also moved earth and rock that had collected along the edges and top of the ice. As the ice melted, rock debris piled up along the glacier's path in bands called moraines.