A massive mudslide occurs in Southern Leyte, Philippines; the official death toll is set at 1,126.
Mudslides, also known as debris flows or mudflows, are a type of mass wasting event where a mass of rock, earth, and other debris moves rapidly down a slope, often with a viscous, muddy consistency. These events typically occur in areas with steep terrain, heavy rainfall, loose soil, and little vegetation to stabilize the slopes.
Triggering Factors: Mudslides are often triggered by natural phenomena such as heavy rainfall, snowmelt, earthquakes, volcanic eruptions, or a combination of these events. Human activities like deforestation, construction, mining, and irrigation can also increase the likelihood of mudslides by destabilizing slopes.
Saturation of Soil: One of the primary factors in mudslide formation is the saturation of soil with water. Heavy rainfall or rapid snowmelt can saturate the soil, reducing its stability and causing it to become more fluid-like.
Loss of Slope Stability: When the soil becomes saturated, the weight of the water can exceed the strength of the soil, causing it to lose cohesion and stability. This can lead to the detachment of a mass of soil, rock, and debris from the slope.
Movement Down Slope: Once the mass becomes detached, gravity pulls it downhill. The presence of water reduces friction between particles, allowing the mass to move more easily. This movement can be slow and gradual or rapid and destructive, depending on factors such as the steepness of the slope, the volume of material involved, and the amount of water present.
Deposit: As the mudslide moves downslope, it can pick up additional debris and gain momentum. It may eventually come to rest when the slope decreases, or it may continue to flow into lower-lying areas, causing damage to structures, roads, and vegetation in its path.