The small Illgraben valley is one of the most geologically unstable regions of Switzerland, and is located south of

Leuk Leuk (french: Loèche-Ville) is a municipality in the district of Leuk in the canton of Valais in Switzerland. On 1 January 2013, the former municipality of Erschmatt merged into the municipality of Leuk.Canton of Valais Valais ( , , ; frp, Valês; german: Wallis ), more formally the Canton of Valais,; german: Kanton Wallis; in other official Swiss languages outside Valais: it, (Canton) Vallese ; rm, (Chantun) Vallais. is one of the 26 cantons forming the Sw ...

Geology and geography

The valley consists of

triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

dolomite Dolomite may refer to: *Dolomite (mineral), a carbonate mineral *Dolomite (rock), also known as dolostone, a sedimentary carbonate rock *Dolomite, Alabama, United States, an unincorporated community *Dolomite, California, United States, an unincor ...

, porous

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

and

quartzite Quartzite is a hard, non- foliated metamorphic rock which was originally pure quartz sandstone.Essentials of Geology, 3rd Edition, Stephen Marshak, p 182 Sandstone is converted into quartzite through heating and pressure usually related to tect ...

,WSL video "Spectacular mudslide research site in Valais", April 2022, see Literature section and due to intense

weathering Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement), ...

, the valley is well-known among geologists as a place to study processes like

erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is distin ...

rockfall A rockfall or rock-fallWhittow, John (1984). ''Dictionary of Physical Geography''. London: Penguin, 1984. . is a quantity/sheets of rock that has fallen freely from a cliff face. The term is also used for collapse of rock from roof or walls of min ...

, debris and mud flows. Likewise, the Illgraben serves as a laboratory to test mudflow warning systems. The Swiss Federal Institute for Forest, Snow and Landscape Research uses radars, microphones and cameras to register mudflow events, and to warn the population of

Leuk Leuk (french: Loèche-Ville) is a municipality in the district of Leuk in the canton of Valais in Switzerland. On 1 January 2013, the former municipality of Erschmatt merged into the municipality of Leuk.Rhône river The Rhône ( , ; wae, Rotten ; frp, Rôno ; oc, Ròse ) is a major river in France and Switzerland, rising in the Alps and flowing west and south through Lake Geneva and southeastern France before discharging into the Mediterranean Sea. At Ar ...

to turn murky until it reaches

Lake Geneva , image = Lake Geneva by Sentinel-2.jpg , caption = Satellite image , image_bathymetry = , caption_bathymetry = , location = Switzerland, France , coords = , lake_type = Glacial lak ...

, which is 90 kilometers (56 miles) downriver. The Pfynwald (French: ''bois de Finges'' or ''forêt de Finges''), a natural reserve and one of the largest continuous

Scots pine ''Pinus sylvestris'', the Scots pine (UK), Scotch pine (US) or Baltic pine, is a species of tree in the pine family Pinaceae that is native to Eurasia. It can readily be identified by its combination of fairly short, blue-green leaves and orang ...

forests of Europe, is located on the alluvial cone of Illgraben's stream, the Illbach. The Pfynwald itself is an important center for

ecological Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overlaps wi ...

studies.

Tourism

A north-easterly view into the Illgraben is possible from the hiking path

Chandolin Chandolin is a village in the district of Sierre in the Swiss canton of Valais. An independent municipality before, it merged on 1 January 2009 with neighboring Ayer, Grimentz, Saint Jean, Saint-Luc and Vissoie to form the municipality of Anniv ...

- Plaine Madeleine. From Susten (650 m,part of Leuk), hikers will first encounter the ''

Bhutan Bhutan (; dz, འབྲུག་ཡུལ་, Druk Yul ), officially the Kingdom of Bhutan,), is a landlocked country in South Asia. It is situated in the Eastern Himalayas, between China in the north and India in the south. A mountainous ...

bridge'', a 134 meter

suspension bridge A suspension bridge is a type of bridge in which the deck (bridge), deck is hung below suspension wire rope, cables on vertical suspenders. The first modern examples of this type of bridge were built in the early 1800s. Simple suspension bridg ...

, before seeing the valley's interior. From there, there is an unmarked trail to the aptly called Steinschlaghütte (English: ''rock fall hut''), or to the alpine lake Illsee and the Illhorn.According to the Swiss map, accessible at http://map.geo.admin.ch

Image gallery

File:Bhutanbrücke-S.jpg , Bhutan bridge at the entrance to the valley File:Illgraben Bed - View North Onyx Interception System.jpg , View of the lower riverbed, with the Onyx SIGINT site visible File:Illgraben LandslideWall.jpg , A scene inside the valley's river bed File:Picswiss VS-69-31.jpg , Pfynwald forest, with the Illgraben and the Illhorn mountain in the background

Literature and further information

* * Video documents by the Swiss Federal Institute for Forest, Snow and Landscape Research: * French, with selectable English subtitles. * Geologists visiting the Illgraben; explanations spoken in English. * {{Cite web , url=https://www.youtube.com/watch?v=3zEyKTJpHXA , title=Murgang im Illgraben, 28. Juni 2000 , date=2016-03-21 , access-date=2022-06-07 , trans-title=Mud slide in Illgraben, 28 June 2000

References

Valleys of Switzerland Geology of Switzerland