Landslides are a geological phenomenon. It is also called a landslip. It includes a wide range of movement from the ground that includes rockfalls, deep failure of slopes and shallow debris flows. It can occur anywhere, whether offshore, coastal, or onshore environments. The primary driving force for landslides to occur is gravity, however, other the stability of the slope is also considered a contributing factor.
Causes of Landslides
When the slope of the land changes from stable to unstable, among other factors, it causes landslides to occur. Landslides causes are classified as either natural or aggravated by human activities.
- Destabilization of slope caused by groundwater (pore water) pressure
- Loss or absence of soil structure, soil nutrients, and vertical vegetative structure
- Erosion of the slope toe caused by ocean or river waves
- Snow melt, glaciers melting or heavy rains causing the slope to weaken through saturation
- Destabilization of slope caused by earthquake-caused liquefaction
- Volcanic eruptions
Aggravated by Human Activities
- Deforestation, cultivation and construction
- Traffic or machinery vibrations
- Work on the earth which modifies the shape of the slope
- Removal of deep-rooted vegetation that keeps the colluvium bound to bedrock
- Construction, agricultural or logging (forestry activities) that causes change in the volume of water that infiltrates the soil
Types of Landslides
There are two different types of landslides: slides and flows. Slides pertain to mass movements where the zone of weakness is distinct from the more stable underlying material. On the other hand, flows refer to different kinds of landslides, each with differing in fundamental ways.
- Translational slide
- Rotational slide
- Block slide
- Debris flow
- Debris avalanche
- Lateral spreads
Recognizing Warning Signs for Landslides
It is necessary to take the extra precaution especially when one lives in steep slopes, neighboring mountain edges, close to drainage ways or natural erosion valleys, as these areas are most susceptible to landslides. The following are warning signals that can be used to recognize upcoming landslides:
- Changes in landscape
- Sticking or jamming doors or windows
- New cracks appearing in tiles, bricks, plasters or foundations
- Gradually developing, widening cracks appearing on the ground, streets, or driveways
- Breaking of underground utility lines
- Breaking of water through the ground surface
- Movement of fences, utility poles or retaining walls
- Tilting trees
- A rumbling sounds that begins faintly and increases in sound as the landslide nears
- The downward sloping of the ground, particularly in one direction
- Shifting under the feet
- Collapsed ground, fallen rocks, etc.
Landslides or landslips can either be caused by natural causes or be aggravated by human actions. To recognize warning signs of natural disasters such as landslides, enroll in First Aid Courses.