Sediment Rock Avalanche
Primary reference(s)
Collins, G.S., 2014. Rock avalanche. In: Encyclopedia of Planetary Landforms. Springer. Accessed 15 October 2020.
USGS, no date. Volcano hazards programme. United States Geological Survey (USGS). Accessed 15 October 2020.
Additional scientific description
Volcanos and earthquakes are commons triggers for rock avalanches. They can occur in all rock types but are associated with rock that is more competent. Large rock avalanches are hypermobile and exhibit more movement than predicted from frictional models incorporating air entrainment, pore pressures or fine bed layers (Hungr et al., 2001, 2014).
Metrics and numeric limits
Rock avalanches pose some of the most dangerous and expensive geological hazards in mountainous terrain. Typical of these was the Frank Landslide, which occurred on 29 April 1903, and involved 110 million tonnes of limestone released from the summit of Turtle Mountain, Alberta. The rock mass that fell was 150 m deep, 425 m high and 1 km wide (Frank Slide Interpretive Centre, no date).
Key relevant UN convention / multilateral treaty
Not identified.
Examples of drivers, outcomes and risk management
A database of 20th-century worldwide catastrophic landslides (USGS, no date) includes six rock slide-debris avalanche events, including one volcano-triggered landslide (St Helens) and three earthquake triggered landslides. The earthquake triggered events resulted in river dams with loss of entire villages Bairaman, Papua, New Guinea in 1986 and Tadzhik Republic: Usoy, 1911 and Khait, 1949.
The Frank Landslide occurred at night. It was triggered by unusual weather conditions influenced also by subsurface mining. The rockslide buried part of the town of Frank with most of the 110 people in its path losing their lives (Frank Slide Interpretive Centre, no date).
As with other types of landslide, rock avalanche can cascade to form river dams with the potential for subsequent release and flooding. Climate change impacts on permafrost have been associated with increasing incidence of rock slide initiation triggered by melting ice or thawing permafrost (USGS, 2018).
References
Frank Slide Interpretive Centre, no date. Canada’s Deadliest Rockslide. Accessed 15 October 2020.
Hungr, O., S.G. Evans, M. Bovis and J.N. Hutchinson, 2001. Review of the classification of landslides of the flow type. Environmental and Engineering Geoscience, VII:221-238.
Hungr, O., S. Leroueil and L. Picarelli, 2014. The Varnes classification of landslide types, an update. Landslides, 11:167-194.
USGS, 2018. Mountain Permafrost, Climate Change, and Rock Avalanches in Glacier Bay National Park, Alaska. United States Geological Survey (USGS). Accessed 15 October 2020.
USGS, no date. Catastrophic Landslides of the 20th Century – Worldwide. United States Geological Survey (USGS). Accessed 15 October 2020.