A landslide is a natural disaster. Most landslides take place when part of a slope breaks away and slides downhill. Landslides usually happen as a result of gravity. Landslides occur when something changes the stability of the slope.
A landslide can cause serious damage to the area around it. It can cause rivers to change course and cause flooding. A landslide can cover sections of roadway cutting off access. Roads buckle under the stress of the ground deformation.
What causes these changes? An increase in underground water can put pressure on a slope from deep beneath the soil. The pressure causes the slope to become unstable. Simple erosion can also cause a slope to become unstable. Erosion happens more often where there are no plants to keep the soil in place. Other times, heavy rains, snow, or snowmelts can cause the soil to loosen. In the winter of 1996-97, severe storms brought heavy rain and snow to Seattle, Washington. The soils became saturated, and more than one hundred landslides were reported in the area. Many people lost their homes in these slides.