1843–1918, American geologist, b. Rochester, N.Y., grad. Univ. of Rochester, 1862. When the U.S. Geological Survey was created in the Dept. of the Interior in 1879 (to replace four surveys in the Dept. of the Interior and the Dept. of War), Gilbert was appointed senior geologist. His Report on the Geology of the Henry Mountains (U.S. Geographical and Geological Survey of the Rocky Mountain Region, 1877, 2d ed. 1880) contains the first description of a laccolithic mountain group, a form of mountain structure that he was the first to recognize and explain. The report introduced concepts of erosion, river development, and glaciation that are incorporated in modern theories of physical geology. One of the publications of the Geological Survey is Gilbert's Lake Bonneville (1890), a study of the ancient lake of which Great Salt Lake is the remnant. He mapped the ancient shores and outlets of the Great Lakes and was the first to recognize that the successive levels of the lakes were caused by the barrier of the receding glacier, which cut off the natural drainage of the region. He also published notable studies on Niagara Falls and the Niagara River, the glaciation and morphology of the Sierra Nevada, and hydraulic mining debris in the Sierra Nevada. In 1899 he accompanied the Harriman Alaskan expedition and wrote the volume Glaciers and Glaciation in its reports.
- See biography by W. M. Davis in the Memoirs of the National Academy of Sciences, Vol. XXI (1926).