Landslides can trigger debris flows that surge downhill at speeds exceeding 100 miles per hour.

Debris flows are a specific type of mass wasting event characterized by a high concentration of solid particles suspended in a fluid matrix. According to the United States Geological Survey (USGS), these flows typically contain at least 50% silt and sand-sized particles mixed with water and larger organic debris. The fluid-like movement is caused by high pore-water pressure, which reduces friction between particles and allows the mass to flow rapidly even on gentle slopes.The 1958 Lituya Bay event remains the most extreme example of landslide-induced displacement. On July 9, 1958, a magnitude 7.8 earthquake along the Fairweather Fault caused 40 million cubic yards of rock to plunge 3,000 feet into Gilbert Inlet. This massive impact displaced enough water to create a wave that stripped trees and soil from the shoreline up to an elevation of 1,720 feet.Modern research using high-resolution LiDAR and satellite imagery allows geologists to map high-risk zones more accurately. Studies by institutions like the University of Washington show that debris flows can exert impact forces strong enough to move boulders weighing several tons. Because they often occur during intense rainfall or rapid snowmelt, they are a primary focus for hazard mitigation in mountainous regions worldwide.