Hanging valley is a valley whose mouth lies high on the side of a larger valley. Hanging valleys typically occur in mountainous areas, where small, tributary glaciers once flowed into larger glaciers. Because of its greater weight, the larger glacier carved out a deeper trough than the smaller glacier did. This accounts for the difference in the levels of the two valley floors. After the ice melted, a hanging valley remained above the main valley’s rim. A stream in a hanging valley may form a waterfall as it tumbles into the valley below.