Landslides in humid mountainous regions may dominate mass wasting on hillslopes. Long periods of quiescence and soil development end when an event such as heavy rain or an earthquake destabilizes soil thereby triggering a landslide. The export of partially weathered bedrock, the burial of organic matter in the slide, and the exposure of less weathered saprolite all strongly affect the biogeochemical cycles for many elements. Fire-flood sequences may be the dominant style of rapid erosion in forested, dry, montane regions. Fire-flood sequences require the development of vegetation that can sustain an extensive hot fire combined with suitable weather conditions.
Burns often promote soil hydrophobicity that prevents infiltration.
If a burn is followed be a large rain storm, the diminished infiltration results in highly erosive runoff and deep erosion. As with landslides, the export of partially weathered bedrock, the incorporation of charcoal and other organic matter into flood deposits, and the exposure of fresh bedrock can strongly affect biogeochemical cycles. Human activities have greatly influenced the size and frequency of these phenomena. The implication to biogeochemical cycles at a regional to global scale may be significant, but much research is needed. Moreover, these phenomena represent major hazards for people living in hazard-prone areas.