Sturzstrom

Movement

Sturzstroms may be triggered, similarly to other types of landslides, by heavy rains, earthquakes, or volcanic activity. They move rapidly, but do not necessarily require water to be present to move, and there is no definite explanation for their kinematic characteristics. One theory, the acoustic fluidization theory, hypothesizes that vibrations caused by the collisions among the rock fragments reduce friction and allow the mass to travel great distances. Another theory involves air pockets forming under the slide and providing a cushion that the slide rides over with very low friction, although the merit of this theory has been called into question by the presence of sturzstroms in vacuums such as on the Moon and Phobos. Observation of slides on Iapetus suggests that tiny contact points between bits of ice debris may heat up considerably during the movement, causing melting and forming a more fluidand thus less friction-limitedmass of material.

The amount of energy in a sturzstrom is much higher than in a typical landslide. Once moving, it can ride over nearly any terrain and will cover much more horizontal ground than downward-sloped ground. Its momentum can even carry the sturzstrom up small hills. The process of detachment, movement and deposition of a sturzstrom can be recorded by seismometers tens of kilometers away. The peculiar characteristics of this seismic signal make it distinguishable from that of small earthquakes. In the large Köfels landslide, which flowed into the Ötztal valley in Tyrol, Austria, deposits of fused rocks, called "frictionite" (or "impactite", or "hyalomylonite"), were found in the landslide debris. This has been hypothesized to be volcanic in origin or the result of a meteorite impact, but the leading hypothesis is that it was due to the large amount of internal friction. Friction between static and moving rocks can create enough heat to fuse rocks to form frictionite.

References

References

1. Hermanns, Reginald. (2013-01-01). "Encyclopedia of Natural Hazards".
2. (2018-01-26). "Shear-Rate-Dependent Behavior of Clayey Bimaterial Interfaces at Landslide Stress Levels". Geophysical Research Letters.
3. (2014-03-04). "Frictional velocity-weakening in landslides on Earth and on other planetary bodies". Nature Communications.
4. (29 July 2012). "Massive ice avalanches on Iapetus mobilized by friction reduction during flash heating". Nature Geoscience.
5. Palmer, Jason. (29 July 2012). "Saturn moon Iapetus' huge landslides stir intrigue". BBC News.
6. Ivy-Ochs S, Heuberger H, Kubik PW, Kerschner H, Bonani G, Frank M, and Schlüchter C. (1998). The age of the Köfels event – relative, ¹⁴C, and cosmogenic isotope dating of an early Holocene landslide in the central Alps (Tyrol, Austria). ''Zeitschrift für Gletscherkunde und Glazialgeologie'', (34):57–70.
7. Kurt Nicolussi, Christoph Spötlb, Andrea Thurnera, Paula J. Reimer (2015). [http://www.sciencedirect.com/science/article/pii/S0169555X15002548 Precise radiocarbon dating of the giant Köfels landslide (Eastern Alps, Austria)], Geomorphology, Volume 243, August 2015, pp. 87–91
8. Collins, G.S.. (2003). "Acoustic Fluidization and the Extraordinary Mobility of Sturzstroms". Journal of Geophysical Research: Solid Earth.
9. Hsü, Kenneth J.. (1975). "Catastrophic Debris Streams (Sturzstroms) Generated by Rockfalls". Geological Society of America Bulletin.
10. (2017-10-10). "Failure mechanism and kinematics of the deadly June 24th 2017 Xinmo landslide, Maoxian, Sichuan, China". Landslides.
11. Erismann, T.H.. (1979). "Mechanisms of Large Landslides". Rock Mechanics.
12. Weidinger JT, Korup O. (2008). "Frictionite as evidence for a large Late Quaternary rockslide near Kanchenjunga, Sikkim Himalayas, India – Implications for extreme events in mountain relief destruction". Geomorphology.