Pisgah Crater, or Pisgah Volcano, is a young
volcanic
A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.
On Earth, volcanoes are most often found where tectonic plates a ...
cinder cone
A cinder cone (or scoria cone) is a steep conical hill of loose pyroclastic fragments, such as volcanic clinkers, volcanic ash, or scoria that has been built around a volcanic vent. The pyroclastic fragments are formed by explosive eruptions o ...
rising above a
lava plain in the
Mojave Desert
The Mojave Desert ( ; mov, Hayikwiir Mat'aar; es, Desierto de Mojave) is a desert in the rain shadow of the Sierra Nevada mountains in the Southwestern United States. It is named for the indigenous Mojave people. It is located primarily in ...
, between
Barstow and
Needles, California
Needles is a city in San Bernardino County, California, in the Mojave Desert region of Southern California. Situated on the western banks of the Colorado River, Needles is located near the Californian border with Arizona and Nevada. The city is a ...
in
San Bernardino County, California. The volcanic peak is around south of historic
U.S. Route 66
U.S. Route 66 or U.S. Highway 66 (US 66 or Route 66) was one of the original highways in the United States Numbered Highway System. It was established on November 11, 1926, with road signs erected the following year. The h ...
-
National Old Trails Highway
National Old Trails Road, also known as the Ocean-to-Ocean Highway, was established in 1912, and became part of the National Auto Trail system in the United States. It was long and stretched from Baltimore, Maryland (some old maps indicate Ne ...
and of
Interstate 40, and west of the town of
Ludlow.
The volcano had a historic elevation of , but has been reduced to due to mining.
History
The volcano was the site of the Mount Pisgah Volcanic Cinders Mine, a cinder quarry that produced pumice for commercial use, the primary end product being railroad ballast for the
Santa Fe Railroad
The Atchison, Topeka and Santa Fe Railway , often referred to as the Santa Fe or AT&SF, was one of the larger railroads in the United States. The railroad was chartered in February 1859 to serve the cities of Atchison and Topeka, Kansas, and S ...
. The mountain is currently owned by Can-Cal Resources Limited, a Canadian company specializing in exploration of precious minerals in California.
Mining has had a severe environmental impact; the top of the mountain has been removed and the sides of this historically symmetrical mountain have been scoured into an irregular shape. The mountain is still occasionally quarried for various cinder products, and sand from the mountain was used to depict the black sands of
Iwo Jima
Iwo Jima (, also ), known in Japan as , is one of the Japanese Volcano Islands and lies south of the Bonin Islands. Together with other islands, they form the Ogasawara Archipelago. The highest point of Iwo Jima is Mount Suribachi at high.
...
in the film ''
Letters from Iwo Jima
is a 2006 Japanese-language American war film directed and co-produced by Clint Eastwood, starring Ken Watanabe and Kazunari Ninomiya. The film portrays the Battle of Iwo Jima from the perspective of the Japanese soldiers and is a companion pie ...
''.
Geography
![Inside one of the Lava Tube Caves at Pisgah](https://upload.wikimedia.org/wikipedia/commons/2/22/Inside_one_of_the_Lava_Tube_Caves_at_Pisgah._This_one_is_SPJ.JPG)
Currently, the crater stands 98 meters (321 feet) above the surrounding High Desert terrain, and has a base diameter of 488 meters (1,600 feet). It has lost much of its original cinder cone shape to ongoing
aggregate
Aggregate or aggregates may refer to:
Computing and mathematics
* collection of objects that are bound together by a root entity, otherwise known as an aggregate root. The aggregate root guarantees the consistency of changes being made within the ...
mining operations, in addition to minor natural
erosion
Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is distin ...
.
The mountain contains a large number of lava tubes, which are frequented by cavers. The most well known cave is the -long SPJ Cave.
Located in the
Basin and Range Province
The Basin and Range Province is a vast physiographic region covering much of the inland Western United States and northwestern Mexico. It is defined by unique basin and range topography, characterized by abrupt changes in elevation, alternating ...
, the Mojave Valley and then the
Cady Mountains
The Cady Mountains are a mountain range in the Mojave Desert and within Mojave Trails National Monument, in San Bernardino County, California.
They are located between Interstate 15 and Interstate 40, just east of Newberry Springs. The range lies ...
lie to the north of the peak, while the
Rodman Mountains
The Rodman Mountains are located in the Mojave Desert, in San Bernardino County, California, United States. The range is located south of Interstate 40 and Newberry Springs, and east of the Ord Mountains and northwest of the Bullion Mountains. They ...
lie to the west. The
Lava Bed Mountains
The Lava Bed Mountains are located in the Mojave Desert in southeastern California, United States. The mountains lie in a northwest-southeasterly direction, and are located almost entirely within the Marine Corps Air Ground Combat Center Twentynine ...
lie to the south, and the
Bullion Mountains
The Bullion Mountains are located in the Mojave Desert of California southeast of the city of Barstow. The mountain range stretches for approximately 50 miles in a northwest-southeasterly direction north of Joshua Tree and Twentynine Palms.
Sinc ...
lie to the southeast.
Recreation
The crater and much of the surrounding lava field are on private property. Despite this, the lava tubes in the area are a somewhat popular and easily accessible destination for
caving. Historic Lavic Siding is to the east, with the
Mojave National Preserve beyond.
Geology
There is no reliable date of when Pisgah Crater last erupted. Some believe that Pisgah Volcano is the youngest vent, of four cinder cones, in the
Lavic Lake volcanic field. There may have been activity at this site as recently as 2,000 years ago; however others believe that the last eruption occurred as early as 20,000 to 50,000 years ago. It is too young for the
potassium-argon dating technique, commonly used on specimens over 100,000 years old; as the volcano is basaltic, finding a reliable source of potassium for dating purposes would be difficult anyway. No charred organic material for
radiocarbon dating
Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of carbon.
The method was dev ...
has been found.
Lava at nearby and similarly active
Amboy Crater is interbedded with Bristol Playa sediments at a depth of about 9 meters (30 feet) which are approximately 100,000 years old. Recent
argon-argon dating reveals an age of approximately 18,000 years ± 5,000 years (~90% certainty) for the most recent flow.
dating with chlorine surface exposure gave a somewhat similar age of 22,500 ± 2,600 years
Lava
Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...
flows extend to the west and to southeast of the cone, containing
basalt
Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...
primarily of the
pahoehoe texture, with some a'a. The flows contain numerous
lava tube
A lava tube, or pyroduct, is a natural conduit formed by flowing lava from a volcanic vent that moves beneath the hardened surface of a lava flow. If lava in the tube empties, it will leave a cave.
Formation
A lava tube is a type of lava ca ...
s and caves. The cindercone volcano itself shows signs of oxidization prominent in the reddish/orange/brown appearance of much of the upper portions.
The volcano is a very popular field site for geology instruction. On some weekends, it is not uncommon to find university classes and professional seminar groups around the mountain. Quarrying operations and geological survey activity also occurs at the mountain every so often.
Eruptive history
The volcano erupted at least three times, emptying the magma chamber below. All three eruptions produced
porphyritic
Porphyritic is an adjective used in geology to describe igneous rocks with a distinct difference in the size of mineral crystals, with the larger crystals known as phenocrysts. Both extrusive and intrusive rocks can be porphyritic, meaning all ...
basalt, although rocks from the first eruptive phase are almost
aphanitic
Aphanites (adj. ''aphanitic''; ) are igneous rocks that are so fine-grained that their component mineral crystals are not visible to the naked eye (in contrast to phanerites, in which the crystals are visible to the unaided eye). This geologic ...
. The first eruption was a basaltic flow that created the extensive lava fields visible from Interstate 40. Due to evidence from intrusive structures, it is believed that the cinder cone was formed around this time, although rocks from this eruptive phase are not present on the surface of the cinder cone. The second phase produced similarly extensive flows, while the third eruption produced substantial amounts of
tephra
Tephra is fragmental material produced by a volcanic eruption regardless of composition, fragment size, or emplacement mechanism.
Volcanologists also refer to airborne fragments as pyroclasts. Once clasts have fallen to the ground, they rem ...
. It is believed that most of the present cinder cone consists of pyroclastic material that originated from this final eruption.
Composition
The lava found around the volcano consists of
a'a and
pahoehoe, with considerable concentrations of
olivine
The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers quickl ...
(weathering to
iddingsite
Iddingsite is a microcrystalline rock that is derived from alteration of olivine. It is usually studied as a mineral, and consists of a mixture of remnant olivine, clay minerals, iron oxides, and ferrihydrites. Debates over iddingsite's non-defi ...
) and
plagioclase
Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more prope ...
. Large amounts of gypsum can be found coating rocks near the cinder cone.
See also
*
Lavic Lake volcanic field
*
Amboy Crater
*
Cima volcanic field
Cima volcanic field is a volcanic field in San Bernardino County, California, close to the border with Nevada. The volcanic field covers a surface area of within the Mojave National Preserve west of the Cima Dome and consists of about 40 volcan ...
**
Mojave National Preserve
**
Providence Mountains State Recreation Area
The Providence Mountains State Recreation Area is located in the Providence Mountains, within the Mojave National Preserve in San Bernardino County, California. It is also home to the Mitchell Caverns Natural Preserve.
Geography
The Recreation ...
**
Mitchell Caverns
*
Coso Volcanic Field
References
*
External links
Volcano World: Pisgah CraterSatellite view of Pisgah Crater
{{Authority control
Natural history of the Mojave Desert
Cinder cones of the United States
Protected areas of the Mojave Desert
Volcanic fields of California
Volcanoes of San Bernardino County, California
Landforms of San Bernardino County, California
Mojave Desert
Volcanoes of California