Grove Karl Gilbert

Grove Karl Gilbert was an American geologist known for combining careful field observation with quantitative physical reasoning about how landscapes form and change. While working with John Wesley Powell's survey of the Rocky Mountain region, Gilbert published The Geology of the Henry Mountains in 1877, an influential early study of how igneous intrusions can dome and deform overlying rock layers. In 1890 Gilbert published a major study of the ancient Lake Bonneville in Utah, in the course of which he described a distinctive type of river delta deposit now called a Gilbert delta, a term still used in sedimentary geology. Gilbert's later work on Basin and Range structure in the western United States, published posthumously in 1928, helped establish foundational principles of landscape evolution, erosion and sediment transport, an area of study now called geomorphology. Gilbert also studied the origin of lunar craters and, after initial hesitation, conducted early experiments supporting the idea that many craters, both on the Moon and on Earth, are formed by the impact of falling bodies rather than volcanic activity. Gilbert joined the United States Geological Survey in 1879 and remained associated with it for the rest of his career, at times serving as acting director.