The mouth of Little Cottonwood Canyon is littered with enormous boulders of granodiorite and granite sitting on metamorphic bedrock that is over a billion years old. These boulders, called glacial erratics, were transported down the canyon by the ice and left behind when it melted.
| The lateral moraine on the north side of the mouth of Little Cottonwood Canyon is covered with glacial erratics. These boulders are out of place, hence the term “erratic”. |