The Flatirons are

rock formation A rock formation is an isolated, scenic, or spectacular surface rock outcrop. Rock formations are usually the result of weathering and erosion sculpting the existing rock. The term ''rock formation'' can also refer to specific sedime ...

s in the

western Western may refer to: Places *Western, Nebraska, a village in the US *Western, New York, a town in the US *Western Creek, Tasmania, a locality in Australia *Western Junction, Tasmania, a locality in Australia *Western world, countries that id ...

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

, near

Boulder, Colorado Boulder is a home rule city that is the county seat and most populous municipality of Boulder County, Colorado, United States. The city population was 108,250 at the 2020 United States census, making it the 12th most populous city in Colora ...

, consisting of flatirons. There are five large, numbered Flatirons ranging from north to south (First through Fifth, respectively) along the east slope of

Green Mountain Green Mountain is a common name for "The Peak", the highest point on Ascension Island, which has gained some fame for claims that it is one of very few large-scale artificial forests. History and vegetation Many early 19th-century accounts, inc ...

(elev. ), and the term "The Flatirons" sometimes refers to these five alone. Numerous additional named Flatirons are on the southern part of Green Mountain, Bear Peak, and among the surrounding foothills.

Etymology

The Flatirons were known as the "Chautauqua Slabs" c. 1900 and "The Crags" c. 1906. There are two hypotheses regarding the origin of the current name, one based on resemblance to old-fashioned

clothes iron A clothes iron (also flatiron, smoothing iron, or simply iron) is a small appliance that, when heated, is used to press clothes to remove wrinkles and unwanted creases. Domestic irons generally range in operating temperature from between to . ...

s, the other based on resemblance to the Flatiron Building completed in 1902.

Geology

Flatirons view from Broomfield, Colorado

The Flatirons consist of conglomeratic

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicat ...

of the

Fountain Formation The Fountain Formation is a Pennsylvanian bedrock unit consisting primarily of conglomerate, sandstone, or arkose, in the states of Colorado and Wyoming in the United States, along the east side of the Front Range of the Rocky Mountains, and a ...

. Geologists estimate the age of these rocks as 290 to 296 million years; they were lifted and tilted into their present orientation between 35 and 80 million years ago, during the

Laramide Orogeny The Laramide orogeny was a time period of mountain building in western North America, which started in the Late Cretaceous, 70 to 80 million years ago, and ended 35 to 55 million years ago. The exact duration and ages of beginning and end of the ...

. The Flatirons were subsequently exposed by erosion. Other manifestations of the Fountain Formation can be found in many places along the Colorado Front Range, including

Garden of the Gods Garden of the Gods (Arapaho: ''Ho3o’uu Niitko’usi’i'') is a public park located in Colorado Springs, Colorado, United States. It was designated a National Natural Landmark in 1971. Name The area now known as Garden of the Gods was f ...

near

Colorado Springs Colorado Springs is a home rule municipality in, and the county seat of, El Paso County, Colorado, United States. It is the largest city in El Paso County, with a population of 478,961 at the 2020 United States Census, a 15.02% increase since ...

, Roxborough State Park in Douglas County, and

Red Rocks Amphitheatre Red Rocks Amphitheatre (also colloquially as simply Red Rocks) is an open-air amphitheatre built into a rock structure in the western United States, near Morrison, Colorado, west of Denver. There is a large, tilted, disc-shaped rock behind ...

near Morrison.

Climbing

The Flatirons on Green Mountain are within the City of Boulder Open Space and Mountain Parks system. They are popular destinations for hikers and rock climbers, with rock grades ranging from easy (5.0) to world-class (5.14b). Of note is the East Face Standard route on the Third Flatiron; guidebook author and longtime climber Richard Rossiter calls it "The best 5.4 in the solar system."

A symbol of Boulder

Images of the numbered Flatirons on Green Mountain are ubiquitous symbols of the city of

Boulder In geology, a boulder (or rarely bowlder) is a rock fragment with size greater than in diameter. Smaller pieces are called cobbles and pebbles. While a boulder may be small enough to move or roll manually, others are extremely massive. In ...

. The area abounds with Flatirons photographs, drawings, paintings, and sculptures. The city government, the

University of Colorado The University of Colorado (CU) is a system of public universities in Colorado. It consists of four institutions: University of Colorado Boulder, University of Colorado Colorado Springs, University of Colorado Denver, and the University o ...

, and many businesses make use of this symbol in their logos, advertisements, and marketing materials. Many businesses also use the word ''Flatirons'' or ''Flatiron'' in their names. In addition, Boulder often is referred to in the tech industry as the "Silicon Flatirons", analogous to Santa Clara Valley's famous nickname. The third Flatiron bore a "CU," for the University of Colorado, in white letters from the 1950s until 1980, when the city painted over the initials to restore the natural look of the stone formation. CU students Dale Johnson and Robert Rowlands climbed the flatiron one night in November 1949 to paint the original "C." The "C" was removed and painted again, with a "U" being added in the 1950s. The letters are still faintly visible under the reddish paint used by the city in 1980.

References

External links

Climbing according to summitPost.orgFlatiron Webcam360 Degree Panoramas Near Flat Irons
* {{Coord, 39.988, N, 105.293, W, type:landmark, display=title Fountain Formation Landmarks in Colorado Climbing areas of Colorado Landforms of Boulder County, Colorado