Geologic hazards



A geologic hazard is one of several types of adverse geologic conditions capable of causing damage or loss of property and life. These hazards can consist of sudden or slow phenomena:
 * avalanches (snow, rock, or air & snow) and its runout
 * earthquakes and earthquake-triggered phenomena
 * fault rupture (displacement of the terrain or ground along a geological fault), recent (active) fault (exhibiting actual movement or seismic activity)
 * forest fires (espec. in Mediterranean areas)
 * ice jams or ice impact (Eisstoß) on rivers or below a glacier
 * landslide (lateral displacement of earth materials on a slope or hillside)
 * mudflows (avalanche-like muddy flow of soft/wet soil and sediment materials, narrow landslides)
 * pyroclastic flows
 * rock falls, rock slides, (rock avalanche) and debris flows
 * torrents (flash floods, rapid floods or heavy current creeks with irregular course)
 * volcanic eruptions, lahars and ash falls.

Rather gradual or slow phenomena are e.g.: Sometime the hazard is instigated by man through the careless location of developments or construction in which the conditions were not taken into account.
 * alluvial cones (e.g. at the exit of canyons or side valleys)
 * caldera development (volcanoes)
 * geyser deposits
 * ground settlement due to consolidation of compressible soils or due to collapseable soils (''see also compaction)
 * ground subsidence, sags and sinkholes
 * liquefaction (settlement of the ground in areas underlain by loose saturated sand/silt during an earthquake event)
 * sand dune migration
 * shoreline and wave erosion
 * thermal springs

Geologic Hazard Evaluation
Geologic hazards are typically evaluated by engineering geologists who are educated and trained in interpretation of landforms and earth process, earth-structure interaction, and in geologic hazard mitigation. The engineering geologist provides recommendations and designs to mitigate for geologic hazards. Mitigation can include avoidance of the hazards or relocation; construction of slope stabilization measures such as earth buttress, retaining walls, diversion walls, shear pins, tiebacks, soil nails or soil anchors; shoreline protection such as revetments; soil or rock improvements such as dynamic compaction, injection of grout or concrete; deep foundations; tunnels; surface and subdrain systems; flood control structures; and other measures.