Serranía de Hornocal up close near Humahuaca

Traditionally in

geomorphology Geomorphology (from Ancient Greek: , ', "earth"; , ', "form"; and , ', "study") is the scientific study of the origin and evolution of topographic and bathymetric features created by physical, chemical or biological processes operating at or ...

, a flatiron is a steeply sloping triangular landform created by the differential erosion of a steeply dipping, erosion-resistant layer of rock overlying softer strata. Flatirons have wide bases that form the base of a steep, triangular facet that narrows upward into a point at its summit. The dissection of a hogback by regularly spaced streams often results in the formation of a series of flatirons along the strike of the rock layer that formed the hogback.Ollier, C. D. (1985) ''Glossary of Morphotectonics,'' 2nd ed. Bureau of Mineral Resources. Geology and Geophysics Record no. 1985/30. Dept. of Geology and Geophysics, Canberra, Australia. 55 pp. Fairbridge, RW (1968) ''Hogback and Flatiron.'' In RW Fairbridge, ed., pp. 524-525, ''The Encyclopedia of Geomorphology'' (Encyclopedia of Earth Sciences, Volume III), Reinhold, New York, 1296 pp. Huggett, JL (2011) ''Fundamentals of Geomorphology.'' Routledge. New York, New York. 516 pp. As noted in some, but not all definitions, a number of flatirons are perched upon the slope of a larger mountain with the rock layer forming the flatiron

inclined Incline, inclined, inclining, or inclination may refer to: *Grade (slope), the tilt, steepness, or angle from horizontal of a topographic feature (hillside, meadow, etc.) or constructed element (road, railway, field, etc.) *Slope, the tilt, steepn ...

in the same direction as, but often at a steeper angle than the associated mountain slope. The name ''flatiron'' refers to their resemblance to an upended, household

flatiron Flatiron or flat iron may refer to various things, often in the shape of a wedge: Objects *Clothes iron * Hair iron Places * Flatiron Building, New York City, at the intersection of 5th & Broadway **Flatiron District, New York City, named afte ...

.Jackson, JA, J Mehl and K Neuendorf (2005) ''Glossary of Geology.'' American Geological Institute, Alexandria, Virginia. 800 pp. The Flatirons near Boulder, Colorado, is both an example of these landforms and the source of their name. Other well-developed flatirons are found in the eastern

Uinta Mountains The Uinta Mountains ( ) are an east-west trending chain of mountains in northeastern Utah extending slightly into southern Wyoming in the United States. As a subrange of the Rocky Mountains, they are unusual for being the highest range in the ...

in northwestern Colorado,Hansen, WR (2005
''The Geologic Story of the Uinta Mountains.''
United States Geological Survey, Reston, Virginia. the

Waterpocket Fold The Waterpocket Fold is a geologic landform that extends from southern Wayne through Garfield and ending in northern Kane counties of southern Utah, United States.''Utah Atlas & Gazeteer,'' DeLorme, 9th ed., 2014, pp. 44, 52, 60-1 The geol ...

Capitol Reef National Park Capitol Reef National Park is an American national park in south-central Utah. The park is approximately long on its northsouth axis and just wide on average. The park was established in 1971 to preserve of desert landscape and is open all ye ...

, the Superstition Mountains near

Phoenix, Arizona Phoenix ( ; nv, Hoozdo; es, Fénix or , yuf-x-wal, Banyà:nyuwá) is the List of capitals in the United States, capital and List of cities and towns in Arizona#List of cities and towns, most populous city of the U.S. state of Arizona, with 1 ...

, and on the flanks of the Marathon Uplift in west Texas.MaCleod, B. (2009
''Southern Margin of the Marathon Basin.''Big Bend Photographs
Texas Geological Press. The term "flatiron" is also used for very small-scale landforms that are known as pediment flatirons and talus flatirons. These

landform A landform is a natural or anthropogenic land feature on the solid surface of the Earth or other planetary body. Landforms together make up a given terrain, and their arrangement in the landscape is known as topography. Landforms include hills, ...

s are small knolls with a triangular to

trapezoid A quadrilateral with at least one pair of parallel sides is called a trapezoid () in American and Canadian English. In British and other forms of English, it is called a trapezium (). A trapezoid is necessarily a convex quadrilateral in Eu ...

al-shaped sloping surface with the long side of this surface as their base and a point at their top. Both pediment flatirons and talus flatirons are associated with the scarps of a

cuesta A cuesta (from Spanish ''cuesta'' "slope") is a hill or ridge with a gentle slope on one side, and a steep slope on the other. In geology the term is more specifically applied to a ridge where a harder sedimentary rock overlies a softer laye ...

mesa A mesa is an isolated, flat-topped elevation, ridge or hill, which is bounded from all sides by steep escarpments and stands distinctly above a surrounding plain. Mesas characteristically consist of flat-lying soft sedimentary rocks capped by a ...

, or

butte __NOTOC__ In geomorphology, a butte () is an isolated hill with steep, often vertical sides and a small, relatively flat top; buttes are smaller landforms than mesas, plateaus, and tablelands. The word ''butte'' comes from a French word me ...

and with their tips directed towards the scarp. Both types of these flatirons are typically separated from the scarp by well-defined

ravine A ravine is a landform that is narrower than a canyon and is often the product of streambank erosion.gullies. These flatirons consist of either talus, in the case of the talus flatirons, or pedisediment and

colluvium Colluvium (also colluvial material or colluvial soil) is a general name for loose, unconsolidated sediments that have been deposited at the base of hillslopes by either rainwash, sheetwash, slow continuous downslope creep, or a variable combinati ...

that cover

pediments Pediments are gables, usually of a triangular shape. Pediments are placed above the horizontal structure of the lintel, or entablature, if supported by columns. Pediments can contain an overdoor and are usually topped by hood moulds. A pedime ...

, in the case of pediment flatirons. Their surfaces are protected by a thin layer of

caprock Caprock or cap rock is a more resistant rock type overlying a less resistant rock type,Kearey, Philip (2001). ''Dictionary of Geology'', 2nd ed., Penguin Reference, London, New York, etc., p. 41.. . analogous to an upper crust on a cake that is ha ...

. The caprock commonly consists of caliche, which is about thick and rarely as much as thick, that has developed in either talus, pedisediment, or colluvium. Talus flatirons lie within the scarp slope – and pediment flatirons occur within the transition zone between scarp and foreland. Pediment flatirons can merge downward into a

fluvial terrace Fluvial terraces are elongated terraces that flank the sides of floodplains and fluvial valleys all over the world. They consist of a relatively level strip of land, called a "tread", separated from either an adjacent floodplain, other fluvial ...

. Both talus and pediment flatirons are the relict remnants of formerly active slope systems that were once part of the scarp's history.Schmidt, K-H (1989) ''Talus and pediment flatirons – erosional and depositional features on dryland cuesta scarps.'' Catena Supplement 14:107-118.Schmidt, K-H (2009) ''Hillslopes as Evidence of Climatic Change.'' In AJ Parsons and AD Abrahams, eds., pp. 675-694, Geomorphology of Desert Environments, 2nd ed., Springer Science+Business Media, New York, New York, 831 pp.

References

External links

*Ball, J. (2009
Flatirons ≠ pyramids, but they're still coolMagma Cum LaudeAmerican Geophysical Union Blogosphere
November 25, 2009. last accessed January 24, 2014. Mountain geomorphology Structural geology Slope landforms Erosion landforms

Flatiron Flatiron or flat iron may refer to various things, often in the shape of a wedge: Objects *Clothes iron * Hair iron Places * Flatiron Building, New York City, at the intersection of 5th & Broadway **Flatiron District, New York City, named afte ...

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See also

References

External links