Glaciers may have ice tributaries that flow into them. These tributaries are not as deep as the trunk glacier, and hence they do not dig as deep. After the glacier retreats, the valleys formed by the tributaries run at an angle to the main glacial valley. Of particular intrest to hikers are Rock Basin Lakes. The appear when a glacier flows down a hill made up of cracked and broken rock.
Water seeps into the cracks and then freezes, causing the cracks to expand.
Hence, the rocks are broken away along the cracks, forming steps of rock. After the glacier retreats, lakes may appear on the steps left behind. These lakes are rock basin lakes. Emerald and Dream Lakes are perhaps the most visited rock basin lakes in the Park. Other visible lakes are Chasm Lake and Peacock Pool below Longs Peak, and the Gorge Lakes visible across Forest Canyon from Trail Ridge Road.