Geological hazard
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A geologic hazard or geohazard is an adverse
Sometimes the hazard is instigated by the careless location of developments or construction in which the conditions were not taken into account. Human activities, such as drilling through overpressured zones, could result in significant risk, and as such mitigation and prevention are paramount, through improved understanding of geohazards, their preconditions, causes and implications. In other cases, particularly in montane regions, natural processes can cause catalytic events of a complex nature, such as an avalanche hitting a lake and causing a debris flow, with consequences potentially hundreds of miles away, or creating a lahar by volcanism.
Marine geohazards in particular constitute a fast-growing sector of research as they involve seismic, tectonic, volcanic processes now occurring at higher frequency, and often resulting in coastal sub-marine avalanches or devastating tsunamis in some of the most densely populated areas of the world [2][3]
Such impacts on vulnerable coastal populations, coastal infrastructures, offshore exploration platforms, obviously call for a higher level of preparedness and mitigation.[4][5]
Speed of development
Sudden phenomena
Sudden phenomena include:
- avalanches (snow or rock) and its runout
- earthquakes and earthquake-triggered phenomena such as tsunamis
- forest fires (espec. in Mediterranean areas) leading to deforestation
- geomagnetic storms[6]
- gulls(chasms) associated with cambering of valley sides
- ice jams (Eisstoß) on rivers or glacial lake outburst floods below a glacier
- landslide (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 avalanche) and debris flows
- torrents (flash floods, rapid floods or heavy current creeks with irregular course)
- liquefaction (settlement of the ground in areas underlain by loose saturated sand/silt during an earthquake event)
- ash falls.
Slow phenomena
Gradual or slow phenomena include:
- alluvial fans (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
- sand dunemigration
- shoreline and stream erosion
- thermal springs
Evaluation and mitigation
Geologic hazards are typically evaluated by
- Geologic hazards may be avoided by relocation. Publicly available databases, via searchable platforms,[7] can help people evaluate hazards in locations of interest.
- The stability of sloping earth can be improved by the construction of retaining walls, which may use techniques such as slurry walls, shear pins, tiebacks, soil nails or soil anchors. Larger projects may use gabions and other forms of earth buttress.
- Shorelines and streams are protected against scour and erosion using revetments and riprap.
- The soil or rock itself may be improved by means such as dynamic compaction, injection of grout or concrete, and mechanically stabilized earth.
- Additional mitigation methods include deep foundations, tunnels, surface and subdrain systems, and other measures.
- Planning measures include regulations prohibiting development near hazard-prone areas and adoption of building codes.
In paleohistory
Eleven distinct
Known hazards
- 2004 Indian Ocean earthquake and tsunami
- 2008 Sichuan earthquake
- 2011 Tōhoku earthquake and tsunami
- The Barrier (located in Garibaldi Provincial Park)
- Usoi Dam a natural landslide dam
-
Eisstoß Feb.2006 Vienna, Austria (Donauinsel)
-
Glacier just above Grindelwald, Switzerland
-
Soil liquefaction during the 1964 Niigata earthquake
See also
- Earthquake engineering
- Physical impacts of climate change
References
- ^ International Centre for Geohazards Archived March 2, 2008, at the Wayback Machine
- ^ de Lange, G.; Sakellariou, D.; Briand, F. (2011). "Marine Geohazards in the Mediterranean: an overview". CIESM Workshop Monographs. 42: 7–26.[1]
- S2CID 249161443.
- ^ Nadim (2006). "Challenges to geo-scientists in risk assessment for sub-marine slides". Norwegian Journal of Geology. 86 (3): 351–362.
- .
- ^ Geologic Hazards NationalAtlas Archived 2010-04-30 at the Wayback Machine
- ^ Toussaint, Kristin (2021-09-29). "Are environmental hazards threatening your home? This website will show you". Fast Company. Retrieved 2022-06-13.
- S2CID 33327812.
- .
External links
- Media related to Geological hazards at Wikimedia Commons
- International Centre for Geohazards (ICG)