Geologic hazards

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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

Huge landslide at La Conchita, Cal, 1995

Eisstoß Feb.2006 Vienna, Austria (Donauinsel)

Glacier just above Grindelwald, Switzerland

[edit] Sudden or slow phenomena (alphabetic order)

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 (can also be slow, see below)
rock falls (tumbling down of rock masses)
rock slides (rock avalanche) and debris flows
torrents (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)

Norris geyser at Yellowstone NP, Sept.2003

geyser deposits (see image)
ground settlement due to consolidation of compressible soils or due to collapseable soils (see also compaction)
land degradation
ground subsidence, sags, other geomorphologic displacements
land uplift, heave (?), post-glacial rebound
liquefaction (settlement of the ground in areas underlain by loose saturated sand/silt during an earthquake event), seismically induced settlement
sea caves, sinkholes, voids (?), erosion
thermal springs, burial or inundation
wandering sand dunes
or other conditions due to geologic, seismic or tectonic forces and movements. Sometime the hazard is instigated by man on by the careless location of developments or construction in which the conditions were not taken into account.

[edit] Geologic Hazard Evaluation

Geologic hazards are evaluated by an engineering geologist educated, trained and experienced in engineering geology for their , investigation and analysis. Often in conjunction with a geotechnical engineer, the engineering geologist is qualified to formulate recommendations for the mitigation of the hazards. Mitigation can include avoidance of the hazards or relocation; construction of slope stabilization measures (earth buttress, retaining walls, diversion walls, shear pins, tiebacks, soil nails or soil anchors, revetments, injection of grout or concrete, deep foundations, tunnels, subdrains), and other measures.