The irregular shoreline of Flathead Lake is discernible in this northeast-looking, low-oblique photograph. The lake [30 miles (48 kilometers) long and 12 to 14 miles (19 to 23 kilometers) wide], located in a depression that remained after a large block of ice retreated during the last ice age, is used for recreation and some irrigation. Kalispell is barely discernible north of the lake. East of the lake are the snow-covered, rugged peaks of the Mission Range, east of which is elongated, glacier-carved Swan Valley. Clouds overhang the peaks of the Swan Range, which is east of Swan Valley. To the east-northeast of Flathead Lake is Swan Lake, and to the west are the lower, less rugged Salish Mountains. Agricultural field patterns appear south of the lake in Flathead Valley.