It is about three to three and one-half miles long and one and one-fourth miles wide.

From its upper end runs a canyon bordered on either side by the highest peaks in this region.

The rocky walls of this canyon terminate on the east side at the head of the lake, but on the west side, a little farther down.
The lake is bordered on each side by an admirably marked debris ridge (moraine) three hundred feet high, four miles long, and one and one-half to two miles apart.

These moraines may be traced back to the termination of the rocky ridges which bound the canyon.

On one side the moraine lies wholly on the plain; on the other side its upper part lies against the slope of Mount Tallac.