Geological hazard
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
Sudden or slow phenomena (alfabetic order)
- avalanches (snow, 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 cañons or side valleys)
- caldera development (volcanoes)
- 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.
Geologic Hazard Evaluation
Geologic hazards are evaluated by an engineering geologist educated, trained and experienced in engineering geology for their recogition, 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.