| The Devils Postpile National Monument | |
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 Basalt columns of Devils Postpile | |
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| Location | Madera County, California, United States |
| Nearest city | Mammoth Lakes, CA |
| Coordinates | 37°37′28″N119°5′4″W / 37.62444°N 119.08444°W /37.62444; -119.08444 |
| Area | 798 acres (323 ha)[1] |
| Created | July 6, 1911 (1911-07-06) |
| Visitors | 109,571 (in 2017)[2] |
| Governing body | National Park Service |
| Website | Devils Postpile National Monument |
Devils Postpile National Monument is aU.S. national monument located nearMammoth Mountain inEastern California. The monument protects Devils Postpile, an unusual rock formation ofcolumnar basalt, "all closely and perfectly fitted together like a vast mosaic."[3] The monument encompasses 798 acres (323 ha) and includes two main attractions: the Devils Postpile formation andRainbow Falls, a waterfall on the Middle Fork of theSan Joaquin River. In addition, theJohn Muir Trail andPacific Crest Trail merge into one trail as they pass through the monument.[4] Excluding a small developed area containing the monument headquarters, visitor center and a campground, the National Monument lies within the borders of theAnsel Adams Wilderness.[5]
The monument was established in 1911 as "Devil Postpile National Monument," (no possessive)[6] but is widely referred to as Devils Postpile National Monument,[7] and has been officially styled as plural without the apostrophe since the 1930s.
An alternate historic name was Devil's Woodpile. According toHistoric Spots in California (1966), "In every scenic freak the sheep-herder recognizes the work of his Satanic majesty. This formation is therefore known to local fame as the Devil's Woodpile."[3]
The monument was once part ofYosemite National Park, but discovery ofgold in 1905 nearMammoth Lakes prompted a boundary change that left the Postpile on adjacentpublic land.[8] Later, a proposal to build ahydroelectric dam called for blasting the Postpile into the river. Influential Californians, includingJohn Muir, persuaded the federal government to stop the demolition and, in 1911, PresidentWilliam Howard Taft protected the area as aNational Monument.[8]
The elevation of the national monument is between 7,200 and 8,200 ft (2,200 and 2,500 m), and the flora and fauna are typical of the western Sierra Nevada at these elevations.[9] The monument area contains animals and plants such asblack bears,pine martens,mule deer,coyotes,[10]quaking aspen,black cottonwood,alder, andwillows,[11]Dark-eyed juncos andwhite-crowned sparrows are common in the summer.[12]
Native wildflowers include:[13]
The most common method for accessing Devils Postpile is via the mandatory shuttle bus operated by Eastern Sierra Transit Authority in the summer months at the price of $15 for an adult,[14] followed by a 1/4 mile walk. The shuttle route begins at Mammoth Mountain Ski Area's Adventure Center and makes several stops throughout the valley and begins operating when the Reds Meadow Road opens in the summer, and continues through Labor Day weekend.
Devils Postpile is also accessible on foot from Mammoth Lakes by hiking over Mammoth Pass and into the Reds Meadow Valley. During the winter months, there are no services available, but adventurers can visit the site via cross-country ski or snowshoe.[15]
Due to the Reds Meadow Road reconstruction project for the 2024 season, entry is limited to Friday starting at 9 AM, all day Saturday, and Sunday until 11 PM, this schedule until September 15, 2024. From then until the winter closure, it’s only open on Saturdays and Sundays from 9 AM to 7 PM, and there’s no shuttle. It’s closed on other days for reconstruction of the road to improve access and safety.[16]
The name "Devils Postpile" refers to a dark cliff ofcolumnar basalt.Radiometric dating indicates the formation was created by a lava flow at some time less than 100,000 years ago.[17] The source of the lava is thought to have been somewhere near Upper Soda Springscampground at the north end of Pumice Flat on the floor of the Middle Fork of theSan Joaquin River, from where it flowed to the site of the Postpile. Estimates of the formation's thickness range from 400 feet (120 m) to 600 feet (180 m). The lava that now makes up the Postpile was near the bottom of this mass.[17]
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 contract while cooling.
Aglacier later removed much of this mass of rock and left a polished surface on top of the columns with very noticeableglacial striations andglacial polish.[17]
The Postpile's columns average 2 feet (0.61 m) in diameter ("The columns vary in size from ten to 30 inches in diameter."[3]), the largest being 3.5 feet (1.1 m), and many are up to 60 feet (18 m) long.
Together they look like tall posts stacked in a pile, hence the feature's name. If the lava had cooled perfectly evenly, all of the columns would be expected to be hexagonal, but some of the columns have different polygonal cross-sections due to variations in cooling. 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.[17] Compared with other examples of columnar jointing, the Postpile has more hexagonal columns. Another feature that places the Postpile in a special category is the lack of horizontal jointing.
Although the basaltic columns are impressive, they are not unique. Basalt columns are a common volcanic feature, and they occur on many scales (faster cooling produces smaller columns). Other notable sites includeSvartifoss inVatnajökull National Park inIceland,Giant's Causeway inNorthern Ireland,Fingal's Cave in Scotland, Titan's Piazza of theMount Holyoke Range inMassachusetts, theGarni Gorge inArmenia, theCyclopean Isles nearSicily,Sheepeater Cliff atYellowstone National Park inWyoming,Basaltic Prisms of Santa María Regla inHuasca de Ocampo,Mexico, the Organ Pipes formation onMount Cargill inNew Zealand,Gilbert Hill inMumbai,Organ Pipes National Park inAustralia and the Column Cape (Russian:Mis Stolbchaty) onKunashir Island, the southernmost of theKuril Islands,Cerro Colorado andMar Brava (Ancud) inChile. Columnar basalt can also be seen in a high desert dry river falls area just north ofLajitas, Texas. The much more massiveDevils Tower National Monument inWyoming is superficially similar but consists of aphonoliteporphyry, formed by theintrusion ofigneous rock.[18]
This article incorporatespublic domain material from websites or documents of theNational Park Service.
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