Sturzstrom

The term sturzstrom, a German word composed of Sturz (fall) and Strom (stream), indicates some large landslides consisting of soil and rock which travel a great horizontal distance when compared to their initial vertical drop — as much as 20 or 30 times. The term is used as a synonym to rock avalanche.[1] Sturzstroms have similarities to the flow of glaciers, mudflows, and lava flows. They flow across land fairly easily, and their mobility increases when volume increases.[2][3] They have been found on other bodies in the Solar System, including the Moon, Mars, Venus, Io, Callisto, Iapetus,[4][5] and Phobos.

Volcano.jpeg
The Mt St Helens landslide was a sturzstrom. The slide took place on the north face, and created the valley-like gap seen here.

Movement

Köfels Landslide
A satellite image of the Köfels landslide showing the debris which flowed into the Ötztal valley. It is estimated that around 3 km3 of material were displaced during this slide about 9800 ± 100 years ago.[6][7]

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.[8] 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 fluid — and thus less friction-limited — mass of material.[5]

Kofelsite (impactite or frictionite) Kofels Structure Austria
Köfelsite (impactite or frictionite), Köfels Structure, Austria. The sample is 4.1 cm (1.6 in) wide.

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.[9] 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.[10] 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.[11][12]

See also

References

  1. ^ Hermanns, Reginald (2013-01-01), "Rock Avalanche (Sturzstrom)", Encyclopedia of Natural Hazards, Encyclopedia of Earth Sciences Series, p. 875, doi:10.1007/978-1-4020-4399-4_301, ISBN 978-90-481-8699-0, retrieved 2018-06-21
  2. ^ Scaringi, Gianvito; Hu, Wei; Xu, Qiang; Huang, Runqiu (2018-01-26). "Shear-Rate-Dependent Behavior of Clayey Bimaterial Interfaces at Landslide Stress Levels". Geophysical Research Letters. 45 (2): 766–777. Bibcode:2018GeoRL..45..766S. doi:10.1002/2017gl076214. ISSN 0094-8276.
  3. ^ Lucas, Antoine; Mangeney, Anne; Ampuero, Jean Paul (2014-03-04). "Frictional velocity-weakening in landslides on Earth and on other planetary bodies". Nature Communications. 5: 3417. Bibcode:2014NatCo...5.3417L. doi:10.1038/ncomms4417. PMID 24595169.
  4. ^ Singer, Kelsi N.; McKinnon, William B.; Schenk, Paul M.; Moore, Jeffrey M. (29 July 2012). "Massive ice avalanches on Iapetus mobilized by friction reduction during flash heating". Nature Geoscience. 5 (8): 574–578. doi:10.1038/ngeo1526.CS1 maint: uses authors parameter (link)
  5. ^ a b Palmer, Jason (29 July 2012). "Saturn moon Iapetus' huge landslides stir intrigue". BBC News. Retrieved 2012-07-29.
  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). Precise radiocarbon dating of the giant Köfels landslide (Eastern Alps, Austria), Geomorphology, Volume 243, August 2015, Pages 87–91
  8. ^ Collins, G.S.; Melosh. "Acoustic Fluidization and the Extraordinary Mobility of Sturzstroms" (PDF).
  9. ^ Hsü, Kenneth J. (1975). "Catastrophic Debris Streams (Sturzstroms) Generated by Rockfalls". Geological Society of America Bulletin. 86 (1): 129–140. Bibcode:1975GSAB...86..129H. doi:10.1130/0016-7606(1975)86<129:CDSSGB>2.0.CO;2. Retrieved 2017-09-24. Sturzstroms can move along a flat course for unexpectedly large distances and may surge upward by the power of their momentum.
  10. ^ Fan, Xuanmei; Xu, Qiang; Scaringi, Gianvito; Dai, Lanxin; Li, Weile; Dong, Xiujun; Zhu, Xing; Pei, Xiangjun; Dai, Keren (2017-10-10). "Failure mechanism and kinematics of the deadly June 24th 2017 Xinmo landslide, Maoxian, Sichuan, China". Landslides. 14 (6): 2129–2146. doi:10.1007/s10346-017-0907-7. ISSN 1612-510X.
  11. ^ Erismann, T.H. (1979). "Mechanisms of Large Landslides". Rock Mechanics. 12 (1): 15–46. Bibcode:1979RMFMR..12...15E. doi:10.1007/BF01241087.
  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. 103 (1): 57–65. Bibcode:2009Geomo.103...57W. doi:10.1016/j.geomorph.2007.10.021.
Brenva Glacier

The Brenva Glacier (French: Glacier de la Brenva, Italian: Ghiacciaio della Brenva) is a valley glacier, located on the southern side of the Mont Blanc massif in the Alps. It is the second longest and eighth largest glacier in Italy, and descends down into Val Veny, close to Entrèves, near Courmayeur. Over the centuries it has experienced a number of major rock avalanches which have shaped the glacier and influenced its movement.

Chaos Crags

Chaos Crags is the youngest group of lava domes in Lassen Volcanic National Park, California. They formed as six dacite domes 1,100-1,000 years ago, one dome collapsing during an explosive eruption about 70 years later. The eruptions at the Chaos Crags mark one of just three instances of Holocene activity within the Lassen volcanic center. The cluster of domes is located north of Lassen Peak and form part of the southernmost segment of the Cascade Range in Northern California. Each year, a lake forms at the base of the Crags, and typically dries by the end of the summer season.

From the base of the crags and extending toward the northwest corner of the park is Chaos Jumbles, a rock avalanche that undermined Chaos Crags' northwest slope 300 years ago. Riding on a cushion of compressed air (see sturzstrom), the rock debris traveled at about 100 miles per hour (160 km/h), flattened the forest before it, and dammed Manzanita Creek, forming Manzanita Lake. In addition to the possibility of forming additional lava domes, future activity at the Chaos Crags could pose hazards from pumice, pyroclastic flows, or rockfalls. Geological study of the Chaos Crags, which continues today, began in the late 1920s, when Howel Williams wrote about its pyroclastic rock deposits, rockfall avalanches, and eruptions. The area is monitored for rockslide threats, which could threaten the local area.

The Crags and the surrounding area's lakes and forests support numerous plant and animal species. The area is not a popular destination for visitors, despite its accessibility. The Chaos Crags and Crags Lake Trail, which lasts about three hours round-trip, runs to the summit, and offers views of volcanic phenomena nearby, as well as the Hat Creek valley and the Thousand Lakes Wilderness.

Coachella Valley

The Coachella Valley ( KOH-ə-CHEL-ə, koh-CHEL-ə) is a desert valley in Southern California that extends approximately 45 mi (72 km) in Riverside County southeast from the San Bernardino Mountains to the northern shore of the Salton Sea. It is the northernmost extent of the vast trough that includes the Salton Sea, the Imperial Valley and the Gulf of California. It is approximately 15 mi (24 km) wide along most of its length, bounded on the west by the San Jacinto Mountains and the Santa Rosa Mountains and on the north and east by the Little San Bernardino Mountains. The San Andreas Fault crosses the valley from the Chocolate Mountains in the southeast corner and along the centerline of the Little San Bernardinos. The fault is easily visible along its northern length as a strip of greenery against an otherwise bare mountain.

The Chocolate Mountains are home to a United States Navy live gunnery range and are mostly off limits to the public. The Coachella Valley is sometimes called the "Desert Empire" to differentiate it from the neighboring urbanized Inland Empire and Imperial Valley. Geographers and geologists sometimes call the area, along with the Imperial Valley to the south, the "Cahuilla Basin" or the "Salton Trough".The valley contains the resort cities of Palm Springs and Palm Desert, and Rancho Mirage, Indio, La Quinta, Indian Wells and Cathedral City, with a total population of almost 500,000 in April, declining to around 200,000 in July and rising to around 800,000 by January. It is sometimes included in the Inland Empire region. Separate from the Inland Empire, it is also a small to medium-sized metropolitan area consisting of Palm Springs, Indio, and other smaller incorporated cities, consolidated into the Coachella Valley, and is sometimes called the Palm Springs/ Indio metropolitan area. Coachella Valley connects with the core of the Greater Los Angeles area to the west via the San Gorgonio Pass, a major transportation corridor that includes Interstate 10 and the Union Pacific Railroad. There is a large population of wintertime residents, known as snowbirds, that at peak times may surpass 100,000, with another 3.5 million annual conventioneers and tourists.

Landslide

The term landslide or less frequently, landslip, refers to several forms of mass wasting that include a wide range of ground movements, such as rockfalls, deep-seated slope failures, mudflows, and debris flows. Landslides occur in a variety of environments, characterized by either steep or gentle slope gradients, from mountain ranges to coastal cliffs or even underwater, in which case they are called submarine landslides. Gravity is the primary driving force for a landslide to occur, but there are other factors affecting slope stability that produce specific conditions that make a slope prone to failure. In many cases, the landslide is triggered by a specific event (such as a heavy rainfall, an earthquake, a slope cut to build a road, and many others), although this is not always identifiable.

Landslide classification

There have been known various classifications of landslides and other types of mass wasting.

For example, the McGraw-Hill Encyclopedia of Science and Technology distinguishes the following types of landslides:

fall (by undercutting)

fall (by toppling)

slump

rockslide

earthflow

rockslide that develops into rock avalanche

List of German expressions in English

A German expression in English is a German loanword, term, phrase, or quotation incorporated into the English language. A loanword is a word borrowed from a donor language and incorporated into a recipient language without translation. It is distinguished from a calque, or loan translation, where a meaning or idiom from another language is translated into existing words or roots of the host language. Some of the expressions are relatively common (e.g. hamburger), but most are comparatively rare. In many cases the loanword has assumed a meaning substantially different from its German forebear.

English and German both are West Germanic languages, though their relationship has been obscured by the lexical influence of Old Norse and Norman French (as a consequence of the Norman conquest of England in 1066) on English as well as the High German consonant shift. In recent years, however, many English words have been borrowed directly from German. Typically, English spellings of German loanwords suppress any umlauts (the superscript, double-dot diacritic in Ä, Ö, Ü, ä, ö and ü) of the original word or replace the umlaut letters with Ae, Oe, Ue, ae, oe, ue, respectively (as is done commonly in German speaking countries when the umlaut is not available; the origin of the umlaut was a superscript E).

German words have been incorporated into English usage for many reasons:

German cultural artifacts, especially foods, have spread to English-speaking nations and often are identified either by their original German names or by German-sounding English names

Developments and discoveries in German-speaking nations in science, scholarship, and classical music have led to German words for new concepts, which have been adopted into English: for example the words doppelgänger and angst in psychology.

Discussion of German history and culture requires some German words.

Some German words are used in English narrative to identify that the subject expressed is in German, e.g. Frau, Reich.As languages, English and German descend from the common ancestor language West Germanic and further back to Proto-Germanic; because of this, some English words are essentially identical to their German lexical counterparts, either in spelling (Hand, Sand, Finger) or pronunciation ("fish" = Fisch, "mouse" = Maus), or both (Arm, Ring); these are excluded from this list.

German common nouns fully adopted into English are in general not initially capitalised, and the German letter "ß" is generally changed to "ss".

Rockslide

A rockslide is a type of landslide caused by rock failure in which part of the bedding plane of failure passes through compacted rock and material collapses en masse and not in individual blocks. While a landslide occurs when loose dirt or sediment falls down a slope, a rockslide occurs only when solid rocks are transported down slope. The rocks tumble downhill, loosening other rocks on their way and smashing everything in their path. Fast-flowing rock slides or debris slides behave similarly to snow avalanches, and are often referred to as rock avalanches or debris avalanches.

Slump (geology)

A slump is a form of mass wasting that occurs when a coherent mass of loosely consolidated materials or rock layers moves a short distance down a slope. Movement is characterized by sliding along a concave-upward or planar surface. Causes of slumping include earthquake shocks, thorough wetting, freezing and thawing, undercutting, and loading of a slope.

Translational slumps occur when a detached landmass moves along a planar surface. Common planar surfaces of failure include joints or bedding planes, especially where a permeable layer overrides an impermeable surface. Block slumps are a type of translational slump in which one or more related block units move downslope as a relatively coherent mass.

Rotational slumps occur when a slump block, composed of sediment or rock, slides along a concave-upward slip surface with rotation about an axis parallel to the slope. Rotational movement causes the original surface of the block to become less steep, and the top of the slump is rotated backward. This results in internal deformation of the moving mass consisting chiefly of overturned folds called sheath folds.

Slumps have several characteristic features. The cut which forms as the landmass breaks away from the slope is called the scarp and is often cliff-like and concave. In rotational slumps, the main slump block often breaks into a series of secondary slumps and associated scarps to form stairstep pattern of displaced blocks. The upper surface of the blocks are rotated backwards, forming depressions which may accumulate water to create ponds or swampy areas. The surface of the detached mass often remains relatively undisturbed, especially at the top. However, hummocky ridges may form near the toe of the slump. Addition of water and loss of sediment cohesion at the toe may transform slumping material into an earthflow. Transverse cracks at the head scarp drain water, possibly killing vegetation. Transverse ridges, transverse cracks and radial cracks form in displaced material on the foot of the slump.

Slumps frequently form due to removal of a slope base, either from natural or manmade processes. Stream or wave erosion, as well as road construction are common instigators for slumping. It is the removal of the slope's physical support which provokes this mass wasting event. Thorough wetting is a common cause, which explains why slumping is often associated with heavy rainfall, storm events and earthflows. Rain provides lubrication for the material to slide, and increases the self-mass of the material. Both factors increase the rate of slumping. Earthquakes also trigger massive slumps, such as the fatal slumps of Turnagain Heights Subdivision in Anchorage, Alaska. This particular slump was initiated by a magnitude 8.4 earthquake that resulted in liquefaction of the soil. Around 75 houses were destroyed by the Turnagain Slump. Power lines, fences, roads, houses, and other manmade structures may be damaged if in the path of a slump.

The speed of slump varies widely, ranging from meters per second, to meters per year. Sudden slumps usually occur after earthquakes or heavy continuing rains, and can stabilize within a few hours. Most slumps develop over comparatively longer periods, taking months or years to reach stability. An example of a slow-moving slump is the Swift Creek Landslide, a deep-seated rotational slump located on Sumas Mountain, Washington.

Slumps may also occur underwater along the margins of continents and islands, resulting from tidal action or a large seismic event. These submarine slumps can generate disastrous tsunamis. The underwater terrain which encompasses the Hawaiian Islands gains its unusual hummocky topography from the many slumps that have taken place for millions of years.

One of the largest known slumps occurred on the south-eastern edge of the Agulhas Bank south of Africa in the Pliocene or more recently. This so-called Agulhas Slump is 750 km (470 mi) long, 106 km (66 mi) wide, and has a volume of 20,000 km3 (4,800 cu mi). It is a composite slump with proximal and distal allochthonous sediment masses separated by a large glide plane scar.

Stappitzer See

Stappitzer See is an Alpine lake in the Hohe Tauern mountain range near Mallnitz in Carinthia, Austria. It is located in the peripheral zone of the Hohe Tauern National Park.

Umhausen

Umhausen is a municipality in the Imst district of state of Tyrol in western Austria. It and is located 17 km southeast of Imst at the Ötztaler Ache in the Ötztal. It has 3078 inhabitants.

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