Geologic hazards

From Wiki.GIS.com

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.:

• 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

Sometime the hazard is instigated by man through the careless location of developments or construction in which the conditions were not taken into account.

[edit] 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.

- Eisstoß Feb.2006 Vienna, Austria (Donauinsel)

Glacier just above Grindelwald, Switzerland

[edit] See also

• Earthquake engineering

[edit] External links

• Glossary Of Landform and Geologic Terms, in National Soil Survey Handbook, Part 629.02(c), United States Department of Agriculture, Natural Resouces Conservation Service