Landslides are a natural or manmade event that occurs when a slope becomes unstable and shifts in a significant manner. They can be quite dangerous when they occur near human habitation and have caused countless deaths around the world. The worst landslide in history occurred in Kansu, China in 1920. It destroyed over 100 cities, many villages and over 180,000 people lost their lives. Let’s take a look at what causes a landslide.
What causes landslides?
Generally speaking gravity is the force that is occurring in a landslide, but there are a variety of factors that can make a slope unstable. These causes of landslides that can be broadly broken up into natural and manmade causes. Some of these causes are enough to cause a landslide by themselves, but is many instances a combination of these causes is common. The following are some of the most common causes of landslides.
- The pressure of groundwater on a slope can cause a landslide.
- Loss of vegetation, soil structure and nutrients can make the soil more prone to movement.
- Erosion of the slope can make it unstable. This can be caused by rivers or waves. Slopes can also weaken rapidly with heavy rain and when glaciers or snow melt.
- Earthquakes can weaken slopes and can cause soil liquefaction. This occurs when the soil loses strength and behaves like a liquid.
- Volcanic eruptions are also a common cause of slope instability.
- Deforestation (logging), agriculture or anything that removes deep rooted vegetation can cause slope destabilization.
- Anything that changes the loads placed on a slope, such as earthwork or blasting, can cause a landslide.
- Vibrations from traffic, machinery and construction can cause slopes to become unstable.
- Certain types of mining can cause a landslide.