Devils Postpile National Monument
IUCN Category III (Natural Monument)
Location:	California, USA
Nearest city:	Mammoth Lakes, CA
Coordinates:	37°35′59″N, 119°04′52″W
Area:	798 acres (3.22 km²)
Established:	July 6, 1911
Visitation:	114,788 (in 2004)
Governing body:	National Park Service

The longer fragments of basalt at the base of the cliff are much larger than a person.

Devils Postpile is a dark cliff of columnar basalt near Mammoth Mountain in eastern California. The postpile was created by a lava flow sometime between less than 100,000 years ago (according to current potassium-argon dating) to 700,000 years ago (according to other dating methods). The source of the lava is thought to have been somewhere near Upper Soda Springs campground at the north end of Pumice Flat on the floor of the Middle Fork of the San Joaquin River, from where it flowed to the site of the Postpile, was impounded by a moraine, and reached a thickness of 400 feet (newer estimate) to 600 feet (older estimate). In any event, the lava that now makes up the Postpile was near the bottom of this mass. The World Conservation Union or International Union for Conservation of Nature and Natural Resources (IUCN) is an international organization dedicated to natural resource conservation. ... A Natural Monument is a natural/cultural feature which is of outstanding or unique value because of its inherent rarity, representative of aesthetic qualities or cultural significance. ... Image File history File links Locator_Dot. ... Image File history File links US_Locator_Blank. ... This article is becoming very long. ... Location within Mono County in the state of California Coordinates: State California County Mono County Mayor Kirk Stapp Area    - City 65. ... July 6 is the 187th day of the year (188th in leap years) in the Gregorian Calendar, with 178 days remaining. ... 1911 (MCMXI) was a common year starting on Sunday (click on link for calendar). ... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... The National Park Service (NPS) is the United States federal agency that manages all National Parks, many National Monuments, and other conservation and historical properties with various title designations. ... Basalt Basalt is an extrusive igneous rock, sometimes porphyritic, and is often both fine-grained and dense. ... Mammoth Mountain is a volcano that lies to the west of the town of Mammoth Lakes, California in the Inyo National Forest. ... Eastern California is not a well-defined term. ... Potassium-argon or K-Ar dating is a geochronological method used in many geoscience disciplines. ... A campsite (or campground) is a place used for camping. ... The San Joaquin River, 330 miles (530 km) long, is the second-longest river in California, United States. ... Moraine at Mono Lake, California, United States Moraines clearly seen on a side glacier of the Gorner Glacier, Zermatt, Switzerland. ...

Because of its great thickness, much of the mass of pooled lava cooled slowly and evenly, which is why the columns are so long and so symmetrical. Columnar jointing occurs when certain types of lava cool; the joints develop when the lava contracts during the cooling process.

A glacier later removed much of this mass of rock and left a nicely polished surface on top of the Postpile with very noticeable glacial striations and glacial polish. A glacier is a large, long-lasting river of ice that is formed on land and moves in response to gravity. ... Glacial grooves caused by the Wisconsin glaciation at Kelleys Island, Ohio Glacial striations or glacial grooves are gouges or grooves cut into the bedrock by glacial ice and meltwater as it slowly ground its way along during one of the Earths Ice Ages or by mountain glaciers. ... Glacial polish is a characteristic of rock surfaces where glaciers have passed over bedrock, typically granite or other hard igneous or metamorphic rock. ...

Devils Postpile was once part of Yosemite National Park, but discovery of gold near Mammoth Lakes prompted a boundary change that left the Postpile on adjacent public land. A proposal to build a hydroelectric dam later called for blasting the Postpile into the river. Influential Californians, including John Muir, persuaded the federal government to stop the demolition and in 1911, President Howard Taft made the area into a United States National Monument. The John Muir Trail and Pacific Crest Trail pass through the monument. Yosemite redirects here. ... General Name, Symbol, Number gold, Au, 79 Chemical series transition metals Group, Period, Block 11, 6, d Appearance metallic yellow Atomic mass 196. ... Location within Mono County in the state of California Coordinates: State California County Mono County Mayor Kirk Stapp Area    - City 65. ... In all modern states, some land is held by central or local governments. ... Hydroelectric dam diagram The waters of Llyn Stwlan, the upper reservoir of the Ffestiniog Pumped-Storage Scheme in north Wales, can just be glimpsed on the right. ... John Muir (1838-1914) John Muir appears on the California quarter John Muir (April 21, 1838 – December 24, 1914) was one of the earliest modern preservationists. ... William Howard Taft I (September 15, 1857–March 8, 1930) was the 27th President of the United States (1909-1913), and the 10th Chief Justice of the United States (1921 - 1930). ... This article discusses national monuments in the context of the United States. ... John Muir Trail is a long-distance trail in California, running 211 miles (340 km) from the Yosemite Valley to Mount Whitney. ... The Pacific Crest Trail is a long-distance mountain hiking and equestrian trail that runs from the United States border with Mexico to its border with Canada. ...

The Postpile's columns average 2 feet in diameter, the largest being 3.5 feet, and many are up to 60 feet long. Together they look like tall posts stacked in a pile, hence the feature's name. In a perfect world, all columnar joints would create hexagon-shaped columns; nature, however isn't perfect. A survey of 400 of the Postpile's columns found that 44.5% were 6-sided, 37.5% 5-sided, 9.5% 4-sided, 8.0% 7-sided, and 0.5% 3-sided.^{[citation needed]} Compared with other examples of columnar jointing, the Postpile has more 6-sided columns. Another thing that places the Postpile in a special category is the lack of horizontal jointing. A regular hexagon In geometry, a hexagon is a polygon with six edges and six vertices. ...

Other images

Park entrance	National Monument	Cross section of column Download high resolution version (750x656, 61 KB)Image taken in September 2003 by Daniel Mayer. ...	Column on side Image taken in September 2003 by Daniel Mayer. ...
Another view of the top Download high resolution version (1200x900, 202 KB)Image taken in September 2003 by Daniel Mayer. ...	Top showing glacial polish Image taken in September 2003 by Daniel Mayer. ...	Another view of the top Download high resolution version (1200x900, 195 KB)Image taken in September 2003 by Daniel Mayer. ...	Overview from base Download high resolution version (1200x951, 172 KB)Image taken in September 2003 by Daniel Mayer. ...

Reference

• Roadside Geology of Northern and Central California, Alt, Hyndman (Mountain Press Publishing Company, Missoula; 2000) ISBN 0-87842-409-1

External links

• Official NPS Site
• Maps and aerial photos Coordinates: 37.6245° -119.0847°
  • Street map from Google Maps or Yahoo! Maps
  • Topographic map from TopoZone
  • Aerial image or topographic map from TerraServer-USA
  • Satellite image from Google Maps or Microsoft Virtual Earth
  • Surrounding area map from the United States Census Bureau
• Location indicator from the United States Census Bureau