A talus cave, also known as a boulder cave, is a type of cave formed by the gaps between one, or more commonly many large boulders. [1] Talus caves can be formed anywhere large boulders accumulate in a pile, such as in scree at the base of a cliff.
A talus cave, also known as a boulder cave, is a type of cave formed by the gaps between one, or more commonly many large boulders. [1] Talus caves can be formed anywhere large boulders accumulate in a pile, such as in scree at the base of a cliff.
Talus caves are formed anywhere with a sufficient accumulation of large rocky material, and thus form in a wide variety of rock- in New England, talus caves have been found in anorthosite, schist, slate, phyllite, conglomerate, marble and sandstone. [2] : 53 Nevertheless, talus caves are more likely to form around outcrops of highly competent rock, such as granite or gneiss, which break into cleanly along fractures. [3] [4]
The exact mechanism of talus cave formation differs with geological context. [5] Along at the bottom of cliff faces, talus caves are primarily created created from the mass movement of rock due to slope failure, usually through landslides creating scree deposits which contain the caves. In steep-sided gorges, talus caves may form as a combination of slope failure and downcutting by a stream or river, where smaller rocks and soil is washed away under large boulders, leaving a cave behind. [3]
In Scandinavia and other recently glaciated areas, many talus caves are the result of neotectonic activity due to post-glacial rebound. [6] [7] These caves are found in fractured roche moutonnée hills, where strong neotectonic earthquakes created large systems of fractures and caves.
Several features on Mars have been found to resemble terrestrial scree, giving rise to the possibility of extraterrestrial talus caves. [5]
Talus caves are usually short, although the longest have up to several kilometers of explorable passages. [1] Examples of long talus caves include Bodagrottorna in Hälsingland, Sweden, with 2,600 metres (8,500 ft) of passage, [8] [5] the Touchy Sword of Damocles cave in New York, United States with over 4,000 metres (13,000 ft) of passage, [2] : 55 [9] and Merrills-Barn Door-And-The Hole-Scotts (MBDATHS) cave in Vermont, with 640 metres (2,100 ft) of passage. [2] : 59 Nevertheless, due to the complex, labyrinthine nature of larger talus caves the true length of many systems is unknown.
Although talus caves are poorly studied compared to other types of caves, in areas not conducive to the formation of solutional caves or lava tubes they may be the most common type of cave. Some talus caves in the Northeastern United States are ice caves, with perennial ice deposits inside the cave passages. [10] Talus caves are important habitats for bats and troglofauna, such as the pseudoscorpion Parobisium yosemite which is endemic to talus caves in Yosemite National Park. [11] [2] [4] A few talus caves have been turned into show caves, such as the caves in the Lost River Reservation and Polar Caves Park in New Hampshire, and the caves in Pinnacles National Park in California. [12]
A cave or cavern is a natural void in the ground, specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deep underground. The word cave can refer to smaller openings such as sea caves, rock shelters, and grottos, that extend a relatively short distance into the rock and they are called exogene caves. Caves which extend further underground than the opening is wide are called endogene caves.
An esker, eskar, eschar, or os, sometimes called an asar, osar, or serpent kame, is a long, winding ridge of stratified sand and gravel, examples of which occur in glaciated and formerly glaciated regions of Europe and North America. Eskers are frequently several kilometres long and, because of their uniform shape, look like railway embankments.
An inselberg or monadnock is an isolated rock hill, knob, ridge, or small mountain that rises abruptly from a gently sloping or virtually level surrounding plain. In Southern Africa a similar formation of granite is known as a koppie, an Afrikaans word from the Dutch diminutive word kopje. If the inselberg is dome-shaped and formed from granite or gneiss, it can also be called a bornhardt, though not all bornhardts are inselbergs. An inselberg results when a body of rock resistant to erosion, such as granite, occurring within a body of softer rocks, is exposed by differential erosion and lowering of the surrounding landscape.
Landforms are categorized by characteristic physical attributes such as their creating process, shape, elevation, slope, orientation, rock exposure, and soil type.
The exposed geology of the Yosemite area includes primarily granitic rocks with some older metamorphic rock. The first rocks were laid down in Precambrian times, when the area around Yosemite National Park was on the edge of a very young North American continent. The sediment that formed the area first settled in the waters of a shallow sea, and compressive forces from a subduction zone in the mid-Paleozoic fused the seabed rocks and sediments, appending them to the continent. Heat generated from the subduction created island arcs of volcanoes that were also thrust into the area of the park. In time, the igneous and sedimentary rocks of the area were later heavily metamorphosed.
Scree is a collection of broken rock fragments at the base of a cliff or other steep rocky mass that has accumulated through periodic rockfall. Landforms associated with these materials are often called talus deposits. Talus deposits typically have a concave upwards form, where the maximum inclination corresponds to the angle of repose of the mean debris particle size. The exact definition of scree in the primary literature is somewhat relaxed, and it often overlaps with both talus and colluvium.
Söderåsen is a northwest–southwest elongated bedrock ridge in Scania in southern Sweden. On Söderåsen is Scania's highest point at 212 m (696 ft) above sea level. It is intersected by several fissure valleys. The ridge extends from Röstånga in the southeast to the Åstorp in northwest.
A shield is a large area of exposed Precambrian crystalline igneous and high-grade metamorphic rocks that form tectonically stable areas. These rocks are older than 570 million years and sometimes date back to around 2 to 3.5 billion years. They have been little affected by tectonic events following the end of the Precambrian, and are relatively flat regions where mountain building, faulting, and other tectonic processes are minor, compared with the activity at their margins and between tectonic plates. Shields occur on all continents.
In archaeology, palaeontology, and geomorphology, lichenometry is a geomorphic method of geochronologic dating that uses lichen growth to determine the age of exposed rock, based on a presumed specific rate of increase in radial size over time. Measuring the diameter of the largest lichen of a species on a rock surface can therefore be used to determine the length of time the rock has been exposed. Lichen can be preserved on old rock faces for up to 10,000 years, providing the maximum age limit of the technique, though it is most accurate when applied to surfaces that have been exposed for less than 1,000 years. Lichenometry is especially useful for dating surfaces less than 500 years old, as radiocarbon dating techniques are less accurate over this period. The lichens most commonly used for lichenometry are those of the genera Rhizocarpon and Xanthoria. The measured growth rates of R. geographicum tends to fall within the range of 0.9–0.3 millimeter per year, depending on several factors, including the size of the lichen patch.
Glacial landforms are landforms created by the action of glaciers. Most of today's glacial landforms were created by the movement of large ice sheets during the Quaternary glaciations. Some areas, like Fennoscandia and the southern Andes, have extensive occurrences of glacial landforms; other areas, such as the Sahara, display rare and very old fossil glacial landforms.
The Stawamus Chief, officially Stawamus Chief Mountain, is a granitic dome located adjacent to the town of Squamish, British Columbia, Canada. It towers over 700 m (2,297 ft) above the waters of nearby Howe Sound. It is one of the largest granite monoliths in the world.
In glaciology, a roche moutonnée is a rock formation created by the passing of a glacier. The passage of glacial ice over underlying bedrock often results in asymmetric erosional forms as a result of abrasion on the "stoss" (upstream) side of the rock and plucking on the "lee" (downstream) side. Some geologists limit the term to features on scales of a metre to several hundred metres and refer to larger features as crag and tail.
Glaciokarst is a geological term that refers to a specific type of karst landscape that been influenced significantly by past glacial activity.
Plucking, also referred to as quarrying, is a glacial phenomenon that is responsible for the weathering and erosion of pieces of bedrock, especially large "joint blocks". This occurs in a type of glacier called a "valley glacier". As a glacier moves down a valley, friction causes the basal ice of the glacier to melt and infiltrate joints (cracks) in the bedrock. The freezing and thawing action of the ice enlarges, widens, or causes further cracks in the bedrock as it changes volume across the ice/water phase transition, gradually loosening the rock between the joints. This produces large chunks of rock called joint blocks. Eventually these joint blocks come loose and become trapped in the glacier.
Qaqa Mach'ay is a limestone cave located in the Yauyos Province of the Lima Region in central Peru, high in the Andes Mountains that was explored and surveyed in 2004 by an international expedition. At 4,930m above sea level, it is the highest surveyed cave in the world. The entrance to the cave is in the mountain named Wamp'una.
Ivö Lake is the largest and deepest lake of Skåne, Sweden, located in the municipalities of Kristianstad and Bromölla in the northeastern part of Skåne County. It covers an area of just under 55 km2 (21 sq mi), with a maximum depth of 50 meters. The lake is the richest in fish species in Sweden, including pike, salmon, burbot, vendace, bream, ide, ruffe, minnow, rudd, and spined loach, rare for this area, which has prompted biodiversity conservation efforts and attention from among others EU Natura 2000. 25-30 different species are regularly caught in the lake. It is very well known among fishing enthusiasts, not only in Sweden but in many countries in Europe.
A rauk is a column-like landform in Sweden, often equivalent to a stack. Rauks often occur in groups called raukfält 'rauk fields'. The limestone rauks of Gotland in the Baltic Sea are among the best known examples.
A blockfield, felsenmeer, boulder field or stone field is a surface covered by boulder- or block-sized rocks usually associated with a history of volcanic activity, alpine and subpolar climates and periglaciation. Blockfields differ from screes and talus slope in that blockfields do not apparently originate from mass wastings. They are believed to be formed by frost weathering below the surface. An alternative theory that modern blockfields may have originated from chemical weathering that occurred in the Neogene when the climate was relatively warmer. Following this thought the blockfields would then have been reworked by periglacial action.
The Scandinavian Mountains or the Scandes is a mountain range that runs through the Scandinavian Peninsula. The western sides of the mountains drop precipitously into the North Sea and Norwegian Sea, forming the fjords of Norway, whereas to the northeast they gradually curve towards Finland. To the north they form the border between Norway and Sweden, reaching 2,000 metres (6,600 ft) high at the Arctic Circle. The mountain range just touches northwesternmost Finland but are scarcely more than hills at their northernmost extension at the North Cape.
The geology of the Yorkshire Dales National Park in northern England largely consists of a sequence of sedimentary rocks of Ordovician to Permian age. The core area of the Yorkshire Dales is formed from a layer-cake of limestones, sandstones and mudstones laid down during the Carboniferous period. It is noted for its karst landscape which includes extensive areas of limestone pavement and large numbers of caves including Britain's longest cave network.