Mass wasting is sometimes triggered when heavy rains or periods of snowmelt saturate surface materials. This was the case in December 1999 when torrential rains triggered thousands of landslides along the coat of Venezuela (see Figure 1.20, p.21) and in 1998 when rains from Hurricane Mitch led to the debris flow shown in Figure 4.24. A case study of another rain-triggered mass-wasting event that occurred at La Conchita, California, in January 2005,is found in box 4.2