San Francisco Volcanic Field
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The San Francisco volcanic field is an area of
volcano A volcano is commonly defined as a vent or fissure 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 oft ...
es in northern
Arizona Arizona is a U.S. state, state in the Southwestern United States, Southwestern region of the United States, sharing the Four Corners region of the western United States with Colorado, New Mexico, and Utah. It also borders Nevada to the nort ...
, north of Flagstaff, US. The field covers 1,800 square miles (4,700 km2) of the southern boundary of the
Colorado Plateau The Colorado Plateau is a physiographic and desert region of the Intermontane Plateaus, roughly centered on the Four Corners region of the Southwestern United States. This plateau covers an area of 336,700 km2 (130,000 mi2) within w ...
. The field contains 600 volcanoes ranging in age from nearly 6 million years old to less than 1,000 years (
Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...
to
Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...
), of which
Sunset Crater Sunset Crater is a cinder cone located north of Flagstaff in the U.S. state of Arizona. The crater is within the Sunset Crater Volcano National Monument. Sunset Crater is the youngest in a string of volcanoes (the San Francisco volcanic fie ...
is the youngest. The highest peak in the field is
Humphreys Peak Humphreys Peak (, "its summit never melts") is the highest mountain and the second most prominent peak after Mount Graham in the U.S. state of Arizona. With an elevation of , it is located within the Kachina Peaks Wilderness in the Coconin ...
, at Flagstaff's northern perimeter: the peak is Arizona's highest at 12,633 feet (3,851.5 m) and is a part of the San Francisco Peaks, an active
stratovolcano A stratovolcano, also known as a composite volcano, is a typically conical volcano built up by many alternating layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with ...
complex.


Description

This
volcanic field A volcanic field is an area of Earth's Earth's crust, crust that is prone to localized volcano, volcanic activity. The type and number of volcanoes required to be called a "field" is not well-defined. Volcanic fields usually consist of clusters ...
seems to have formed from a geological hotspot. As the North American Plate moves over the spot, new volcanoes appear. Thus, the newest volcanoes are at the east side of the field. Most of the volcanoes are
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 ...
cinder cone A cinder cone or scoria cone is a steep, volcanic cone, conical landform of loose pyroclastic rock, pyroclastic fragments, such as volcanic ash, clinkers, or scoria that has been built around a volcanic vent. The pyroclastic fragments are forme ...
s, but there are also large
lava dome In volcanology, a lava dome is a circular, mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions ...
s consisting of
rhyolite Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture (geology), texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained matri ...
and
dacite Dacite () is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite. ...
. Given that Sunset Crater is such a young volcanic feature of this area and that eruptions have occurred every several thousands of years in frequency, it is likely that there will be a future eruption in the San Francisco Volcanic field. However, it is impossible to predict when and exactly where a new eruption might occur. The
United States Geological Survey The United States Geological Survey (USGS), founded as the Geological Survey, is an agency of the U.S. Department of the Interior whose work spans the disciplines of biology, geography, geology, and hydrology. The agency was founded on Mar ...
(USGS) says that a future eruption would likely be in the eastern side of the volcanic field, where the most recent volcanic activity has occurred. Such an eruption is likely to be small and pose little hazard due to the remoteness of the area.


Visitation and usage

Popular tourist and hiking destinations in the volcanic field include the Kendrick Mountain Wilderness, 20 miles northwest of Flagstaff; and Sunset Crater. Sunset crater has a hiking trail along an
Ê»aÊ»Ä 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 unde ...
lava flow to its base. Areas of the volcanic field have been used by
NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
for testing techniques for exploration in a simulated extraterrestrial terrain environment.
NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
has also conducted the Desert Research and Technology Studies (DRATS) tests here.


Notable vents


See also

*
List of volcanoes in the United States This article contains a list of volcanoes in the United States and its territories. Alaska American Samoa Arizona California Colorado Hawaii Idaho Illinois Louisiana Michigan Mississippi Missouri Nevada Ne ...
* List of volcanic fields


References


External links


Satellite view of San Francisco Volcanic Field
{{Authority control Colorado Plateau Landforms of Coconino County, Arizona Polygenetic volcanic fields Regions of Arizona Volcanic fields of Arizona Miocene volcanism Pliocene volcanism Pleistocene volcanism Holocene volcanism de:San Francisco Peaks