Formal/Scientific name: mushroom rocks, perched rocks and pedestal rocks .
Designations in other languages: zeugen, which means witness or onlooker
in German.
in German.
Cause/Method of Creation: The supporting column of mushroom and pedestal rocks are caused by etching, differential weathering , and natural sandblasting of sedimentary deposits. A smoothly rounded top (as opposed to a top with rough edges) is created by spheroidal weathering into a form resembling a mushroom.
Long before the mushroom shapes begin to form, a sedimentary rock bed has been created by deposition, burial and lithification leaving an erosion resistant layer above softer sediment layers. Joints and fractures form in the upper layer, allowing faster erosion of the soft strata below. Abrasion near the ground by windblown sand, cause the lower portion of a rock mass to be undercut leaving the upper portion unaffected. The higher off the ground the wind is, the faster it moves and can sandblast harder, but the less sand it can carry. The greatest erosion will occur at the height of the optimum balance of wind speed and sand grain size (see illustration below). The base may be highly polished as it receives the most etching from fine grains.
Note: There is considerable confusion in the use of the labels; mushroom, perched, balanced, pedestal, table and chimney rocks, earth pillar, hoodoo, yardang, ruiniform karst, goblin and demoiselle. This cross naming occurs in both common usage and in academic writings.
For example, the name hoodoo is used in Goblin Valley State Park, Utah, to name the landforms described in this blog entry. Elsewhere in Utah, at Bryce Canyon National Park, the name hoodoo is used locally to describe a chimney rock . It seems that the names hoodoo and goblin are often used for a landform that has an anthropomorphic (human) shape regardless of its method of formation.
The landforms known as balanced, table and chimney rocks, earth pillar, yardang, ruiniform karst, and demoiselle are either similar in shape but formed by a different process than a mushroom rock, or are a different shape formed by a similar process. These landforms will be described in future bogs. The name hoodoo is included in this blog for those who are familiar with this label, although the term seems to be used mostly regionally (and ambiguously) in the American Southwest.
Formation Table: Mushroom/pedestal rocks are…
Exogenic forms (on or near the earths surface), created by
Weathering–via the Mechanical Agent of spheroidal Weathering
and Erosion–via the Transportation Force of wind
Exogenic forms (on or near the earths surface), created by
Weathering–via the Mechanical Agent of spheroidal Weathering
and Erosion–via the Transportation Force of wind
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| Mushroom Rock formation table |
Variations: May have rounded tops or tops with rough edges depending on the substance of the upper sediment layers.
Aerial View: Having an entirely different appearance form the air, the identifying feature of the pedestal on a mushroom rocks isn’t visible and therefor impossible to identify without already knowing the location coordinates. The Google Earth photo below shows a large concentration of mushroom
rocks represented by the small bumps.
rocks represented by the small bumps.
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| credit: Google Earth |
Topo Map View: This is the USGS topographic map for Goblin Valley State Park, UT, which is shown in the map section below. There are no contour marks indicating the mushroom rock formations (they would be scattered around the red number ‘10’ near the center of the map). This may be because the contour interval of the map is 40 feet and the ‘goblins’ avg. about 15 feet in height.
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| credit: USGS |
Physical Locations: The coordinates for where mushroom rocks can be found:
38°34′00″N 110°42′36″W – Goblin Valley State Park, Hanksville, Utah, U.S.
38°43’34”N 098°01’47”W – Mushroom Rock State Park, Marquette, Kansas, U.S.
40°12'23"N 002°00'24"W – La Ciudad Encantada, Cuenca, Spain
Access Difficulty: Depends on the surrounding terrain and accessibility.
Natural Decay/Destruction: Eventually the etched middle section of the pedestal, or mushroom stem, becomes too weak to support the heavier cap and topples over, leaving both the de-capped stem and separated bolder to erode by wind-borne sand and other erosional elements.
Effect on Environment: [Referenced sources have provided no information on this topic. As new sources are discovered, further information may be added to this blog.]
Effect on Humans:This landform has no known negative effect on humans, however mankind seems to be sufficiently intrigued by these people-like shapes that they have created nature parks around especially interesting examples (see Physical Locations above). The dramatic mushroom rocks at La Ciudad Encantada were used as background scenery for the movies The Valley of Gwangi and Conan the Barbarian.
Humans attempt to alter and the consequences: [Referenced sources have provided no information on this topic. As new sources are discovered, further information may be added to this blog.]
Web Sites: Links to further information.
Mushroom Rock State Park
Pedestal Rock Scenic Area at Ozark-St. Francis National Forests
