The surrounding mesas are capped with cliffs and rocky spires, evidence of violent volcanic eruptions some 30 million years ago. These formed the West Elk Mountains to the north. Later volcanic episodes to the south formed Southwestern Colorado's scenic San Juan Mountains, and spewed vast quantities of ash over this area. The Gunnison River readily cut down through this volcanic matter, but below lay the tough, ancient rock that has been exposed in Black Canyon. This canyon lends the fjord-like character to Morrow Point Lake's steep, rock walls.
Crystal Lake is also steep-walled.
Blue Mesa's lake bed formed in less-resistant volcanic mudflow materials. As these eroded beneath solidified volcanic layers, spires formed. You can see a fine example of this formation when hiking the Dillon Pinnacles Trail . The most striking feature of the lower lakes is the spire-like Curecanti Needle. It is best viewed from the tour boat on Morrow Point Lake.