Physical and geological nature of the Indian Peaks, Colorado Front Range

Rolling hills, incised by great valleys, rise gradually from the eastern plains in giant steps to abundant glaciated valleys, many big cirques, remnants of old upland surfaces above 3500 m, and a few tiny glaciers. West of the Divide, excavation by vigorous streams and massive glaciers formed an impressive range of west-facing peaks. Evidence of Pre-Bull Lake glaciation is scarce and scattered. Bull Lake glaciation produced extensive valley glacier systems on both sides of the Divide, excavating deep cirques and forming broad now-subdued moraines. Pinedale glaciation resulted in as many, but slightly shorter, glacier systems. Neoglaciation of three episodes left small cirque moraines or large rock glaciers in most cirques.