Landslide is a type of “mass wasting.” Mass wasting is down slope movement of soil and/or rock under the influence of gravity. A landslide is a movement of mass rock, debris, or earth down a slope. The failure of the slope happens when gravity exceeds the strength of the earth materials. This happens because of many factors.
Erosion by rivers, glaciers or oceans can overly steepen slopes.
- Addition of moisture – Moisture equals weight and water from heavy rainfall, flooding, rapid snow melting, glacier melting, and an increased water table can all saturate the hillside and cause a landslide. El Nino, the weather phenomenon that can increase precipitation, led to thousands of landslides in 1982-83 and 1997-1998.
Shocks and Vibrations – Earthquakes tend to produce the largest and most destructive landslides. The earthquake-induced Alaskan landslide of 1964 happened when the vibrations disrupted the clay soil particles and the water contained in them rose to the surface.
- Overdevelopment – Human activities such as construction, building, transportation, building dams and canals, and mining can disturb large volumes of earth materials. In fact, landslide damage is increasing every year as our population expands further into hilly regions. The San Francisco Bay region is turbulent enough on its own, but as more people overdevelop the land becomes less and less stable. The picture to the right displays the devastating effects of building too close to a hill with landslide potential.
- Deforestation- Humans always chop down trees to fulfill their demands on items. After chopping down the trees, the roots of the trees die. These roots’ job was suppose to hold the soil together but since their dead, the soil is no longer held together. The soil is now loose. When the strong wind blows, or the heavy rain pours, these loosed soil will slowly fall off causing landslide.