Scenic Pettit Lake lies at the edge of Sawtooth Wilderness Area in Idaho. Parks Peak (left) and Imogene Peak (right) in background. Mountain cabins surround this lake, but it is still oligotrophic with Secchi depth transparencies up to 18 m. The granitic Sawtooth Mountains and a relatively uncontaminated airshed yield few nutrients to the lake. Biogenic meromixis has created a layer 10-m thick(131-160 ft) at the bottom of this 50-m lake that does not mix when the lake undergoes seasonal circulation in the spring and fall. Photo, October 2003.