Geological hazard

A geologic hazard or geohazard is an adverse geologic condition capable of causing widespread damage or loss of property and life. These hazards are geological and environmental conditions and involve long-term or short-term geological processes. Geohazards can be relatively small features, but they can also attain huge dimensions (e.g., submarine or surface landslide) and affect local and regional socio-economics to a large extent (e.g., tsunamis).

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

Such impacts on vulnerable coastal populations, coastal infrastructures, offshore exploration platforms, obviously call for a higher level of preparedness and mitigation.

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

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

rockfalls, rock slides, (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)

volcanic eruptions, lahars and ash falls.

Slow phenomena

Gradual or slow phenomena include:

alluvial fans (e.g.