The changing Earth's surface affects society through landslides, land subsidence, floods and other natural hazards. These disasters can be both deadly and costly to society: the Thistle landslide was the most costly single landslide event in U.S. history with costs exceeding $400 million. Land began shifting in Thistle, Utah in 1983 because of groundwater buildup from heavy rains during the previous fall and the melting of deep snowpack from the winter. Within a few weeks, the landslide dammed the Spanish Fork River, destroying U.S. Highway 6 and the main line of the Denver and Rio Grande Western Railroad. The landslide dam caused flood waters to rise which in turn led to lead the inundation of the surrounding area. The town of Thistle was completely obliterated.