Preston Ercelle Cloud, Jr. (September 26, 1912 – January 16, 1991) was an eminent American earth scientist, biogeologist, cosmologist, and paleontologist. He served in the United States Navy (in which he was a bantamweight boxing champion), and led several field explorations of the U.S. Geological Survey. In academia, he was member of faculty of Harvard University, University of Minnesota, University of California, Los Angeles, and lastly University of California, Santa Barbara. He was best known for his work on the geologic time scale and the origin of life on Earth, and as a pioneering ecologist and environmentalist. He was credited with coining the term "biogeology." His works on the significance of Cambrian fossils in the 1940s led to the development of the concept "Cambrian explosion," for which he coined the phrase "eruptive evolution."