CORE UNIT: PATTERNS AND PROCESSES IN THE PHYSICAL ENVIRONMENT
Fig. 11 The Armero Lahar of 1985 Landslides and slumps
Main processes: a trigger, gravity Example: South-east Brazil These occur when rock or sediment suddenly moves downhill along well-defined surfaces which may be flat or curved. The common term for them is landslide.
IN DEPTH - Rotational slumps
Rotational slumps are very common in Ireland along soft coastlines made of glacial till. In a rotational slump, a slab of earth slips along a curved surface and rotates back on itself as it slides downslope. Water helps the slump or landslide to occur by reducing the sticking ability (friction) of the soil particles. Coastal areas are often at risk from rotational slumps as the sea undercuts the base of such cliffs. Rotational slumps may be observed along the Louth coastline north of
Fig. 12 A slump on the Louth coastline
Clogher Head. Every winter landslides/slumps occur on soft coastlines around Ireland. The rail link between Dublin and Greystones has been damaged in this way.