The Beartooth Mountains are the most scenic set of mountains in America that are not in a national park. The Beartooth Highway between the town of Red Lodge, Montana and Yellowstone National Park, Wyoming traverses the Beartooth Mountains and provided ready access to numerous rock exposures. The rocks in the Beartooths are principally Archean-aged, high-grade metamorphic rocks. Lithologies I have observed in this area include gneiss, migmatite, quartzite, amphibolite, serpentinite, chromitite, meta-iron formation, garnet-biotite metamorphite, plus dikes of diabase and alaskite granite.

The landscape here is a glacially and fluvially eroded high plateau. The glacial erosion occurred during the Pleistocene. The deep blue body of water is one of the Twin Lakes, which sit in the floor of a cirque. Cirques are bowl-shaped depressions or basins at the head of a mountain valley, carved out by alpine glaciation. The are usually one to three miles across and typically 500 to 2500 feet deep. Individual lakes in a cirque are called tarns. A string of tarns in a cirque is referred to as pater noster lakes.