| Paternoster lakes (named for their imagined resemblance to rosary beads) are a series of lakes that form in the low spots of a u-shaped valley. They are linked by a stream that flows through the valley. The presence of such lakes is diagnostic of recent glaciation, as rivers cannot cut basins, but rather, attempt to fill them from upstream and drain them from downstream.The number of lakes in a trough can vary as a function of the weakness, jointing, and lithology of the underlying bedrock. Glaciers can also vary in erosive power along their length based on bed temperature, valley steepness, and extending or compressive flow. The lakes shown occupy the Grinnell Creek valley below the Grinnell Glacier (behind the camera), Glacier National Park, Montana. Note the difference in color between Grinnell lake (closest to the camera) in which silt from Grinnell Glacier outwash is deposited, and Josephine lake (second from the camera), which is much clearer. The "bathtub ring" around Sherburne lake (farthest from the camera) results from management of water level by a dam. |  |