An earthquake off the coast of Peru in 1970 started a rockfall which accelerated to more than 170 miles per hour and buried more than 18,000 people. Flows are landslides that behave like fluids. Mudflows involve wet mud and debris. Earthflows involve wet, claylike material. Solifluction is the downslope flow of soil that occurs on arctic and alpine hillsides when thawed ice or snow saturates the soil cover.
Landslides commonly occur with other major natural disasters, such as earthquakes and floods.
The 1980 eruption of Mount St. Helens in Washington was preceded by the development of a large landslide on the north side of the volcano. The Northridge earthquake in 1994 in the San Fernando Valley triggered thousands of landslides in the Santa Susanna Mountains north of the epicenter. Even though landslides are generally not as spectacular or costly as earthquakes, major floods, hurricanes and some other natural catastrophes, they are more widespread and may cause more property loss than any other geologic hazard. Much of the damage attributed to earthquakes and intense storms is really due to landslides. The most expensive landslide in U.S. history occurred in Thistle, Utah, in the spring of 1983.