lesson 4: landslides and sinkholes

• landslide is defined as the movement of a mass of rock, debris, or earth down a slope. these are a type of "mass wasting," which denotes any down-slope movement of soil and rock under the direct influence of gravity
• geological - physical characteristics of the rock and mineral composition and feature of the slope
• morphological - a slope with decreased vegetation cover due to fire or drought is highly prone to landslides
• human activity - agriculture, construction, irrigation, deforestation, excavation water leakage
• flow - the landslide movement is marked by high speed due to the fluidity and consistency of water
• topple - characterized by the tumbling over a blocked unit or units due to gravity, the added force exerted by neighboring units, and water in the fissures
• slump - sthe sliding mass movement of materials along an arched portion of the slope
• slide - happens along weak portions of the slope such as fault, joint, or bedding plane.
• creep - the unnoticeable gradual motion of material characterizes the type of landslide movement
• fall - bouncing or rolling happens in this type of landslide movement
• sinkhole is a hole in the ground caused by removal of material below the ground and either collapse of gradual subsidence of the surface into the resulting void; forms when water dissolves surface rock
• since a thin layer of soil or vegetation covers the limestone bedrock, rainwater finds its way into spaces within the bedrock and dissolves the rocks, gradually forming the dissolution sinkhole, or limestone-solution sinkhole
• cover-subsidence sinkhole tend to develop gradually where the covering sediments are permeable and contain sand
• cover-collapse sinkhole occur in the soil of other loose material overlying soluble bedrock