Dwight Raymond "Rocky" Crandell (25 January 1923 – April 6, 2009) was an American volcanologist who alongside Donal R. Mullineaux correctly predicted that Mount St. Helens would erupt before the end of the 20th century.
Born in Galesburg, Illinois, Crandell fought in World War II as a lieutenant in an Army mortar platoon.
He was placed at the USGS office in Colorado where he met Donal R. Mullineaux with whom he began to work on the theory that Mount St. Helens will erupt, before the end of the century.
They proved that about 5,600 years earlier, the summit of Mount Rainier had collapsed and caused a landslide filling some valleys up to 400 feet deep.
That awakened the recognition that a similar event could endanger hundreds of thousands of people living atop the ancient mudflows.