Mushroom in Timna Park in summer 2011 (1)

A mushroom rock, also called rock pedestal, or a pedestal rock, is a naturally occurring rock whose shape, as its name implies, resembles a mushroom. The rocks are deformed in a number of different ways: by

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 dis ...

and

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) ...

, glacial action, or from a sudden disturbance. Mushroom rocks are related to, but different from, '' yardang''. A mushroom rock, rock pedestal, or gour is a typical

mushroom A mushroom or toadstool is the fleshy, spore-bearing fruiting body of a fungus, typically produced above ground, on soil, or on its food source. ''Toadstool'' generally denotes one poisonous to humans. The standard for the name "mushroom" is ...

-shaped landform that is formed by the action of wind erosion. At an average height of from the base, the material-carrying capacity of the wind is at its maximum, so abrasion (erosion by wind in which transported materials hit an exposed rock surface and polish it or scratch it) is also maximized. In some cases, harder rocks are arranged horizontally over a softer rock, resulting in such erosion.

Erosion

Usually found in desert areas, these rocks form over thousands of years when wind erosion of an isolated rocky outcrop progresses at a different rate at its bottom than at its top. Abrasion by wind-borne grains of sand is most prevalent within the first above the ground, causing the bases of outcrops to erode more rapidly than their tops. Running water can have the same effect. An example of this type of mushroom rock is the one in Timna Park, Israel. Occasionally, the chemical composition of the rocks can be an important factor; if the upper part of the rock is more resistant to chemical erosion and weathering, it erodes more slowly than the base. For example, erosion attributed to chemical weathering at the base of the rock due to the collection of dew near the surface. A mushroom rock may ultimately form from an originally flat area of hard rock overlying soft rock, similar to the pattern of rocks that form a

waterfall A waterfall is a point in a river or stream where water flows over a vertical drop or a series of steep drops. Waterfalls also occur where meltwater drops over the edge of a tabular iceberg or ice shelf. Waterfalls can be formed in severa ...

. Weathering of the exposed hard rock layer eventually exposes the lower rock to erosion from wind, water, salt intrusion, etc., depending on local conditions. The layer of softer rock is more readily eroded, leading to the formation of a depression or blowout. The overlying harder rocks are resistant to this process, and may ultimately end up as isolated mushroom rocks standing above the new, lower plain. The nature of wind erosion is that it concentrates a few feet over the ground - wind speeds increase with height, but sediment load reduces. This means that the combination of highest sediment loads and fastest wind speed exist a few feet over the ground, leading to the characteristic narrowing of the support pedestal at this height.

Glacial action

In contrast to a mushroom rock formed by erosion of a single rock, these mushrooms are a type of

balancing rock A balancing rock, also called a balanced rock or precarious boulder, is a naturally occurring geological formation featuring a large rock or boulder, sometimes of substantial size, resting on other rocks, bedrock, or on glacial till. Some formati ...

that formed from two separate rocks, one of which came to rest on top of the other. Typically, the uppermost rock was transported and deposited by the slow action of a

glacier A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such as ...

. The lower part of the rock formation might or might not have also undergone a degree of erosion to accentuate the mushroom shape. Examples of this type of rock are Mushroom Rock in

Chickamauga and Chattanooga National Military Park Chickamauga and Chattanooga National Military Park, located in northern Georgia and southeastern Tennessee, preserves the sites of two major battles of the American Civil War: the Battle of Chickamauga and the Siege of Chattanooga. A detailed h ...

Tennessee Tennessee ( , ), officially the State of Tennessee, is a landlocked state in the Southeastern region of the United States. Tennessee is the 36th-largest by area and the 15th-most populous of the 50 states. It is bordered by Kentucky to th ...

, and ''Le Champignon'' in Huelgoat, France.''Le Champignon''
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Examples

* Sierra de Organos National Park,

Sombrerete Sombrerete () is a town and municipality located in the northwest of the Mexican state of Zacatecas, bordering the state of Durango. It was founded in 1555 by Spanish conquistador Juan de Tolosa as a mining center, due to the wealth that the mine ...

, Mexico *

Ciudad Encantada The Ciudad Encantada (English: Enchanted City) is a geological site near the city of Cuenca, in the autonomous community of Castilla–La Mancha, Spain in which the erosive forces of weather and the waters of the nearby Júcar river have forme ...

, Cuenca, Castile-La Mancha, Spain *

Goblin Valley State Park Goblin Valley State Park is a state park of Utah, in the United States. The park features thousands of hoodoos, referred to locally as goblins, which are formations of mushroom-shaped rock pinnacles, some as tall as several yards (meters). The ...

, Utah, United States * Gülşehir, Nevşehir, Turkey *

Mushroom Rock State Park Mushroom Rock State Park is noted for its mushroom rock formations. It is located in the Smoky Hills region of north-central Kansas in Ellsworth County, Kansas, United States. These rocks are the remains of beach sands and sediments of the ...

, Kansas, United States * Phae Mueang Phi, Thailand * The stone mushrooms, Bulgaria * Hopewell Rocks, New Brunswick, Canada *White Desert, Egypt *

Wadi Rum Wadi Rum ( ar, وادي رم ''Wādī Ramm'', also ''Wādī al-Ramm''), known also as the Valley of the Moon ( ar, وادي القمر ''Wādī al-Qamar''), is a valley cut into the sandstone and granite rock in southern Jordan, about to the east ...

, Jordan

References

External links

Ciudad Encantada - Visitor information

Mushroom Rock State Park, Ellsworth County, Kansas
{{DEFAULTSORT:Mushroom Rocks Rock formations Erosion landforms

Erosion

Glacial action

Examples

See also

References

External links