Kilbourne and Hunts Holes and White Sands

Kilbourne Hole is a

maar A maar is a broad, low-relief volcanic crater caused by a phreatomagmatic eruption (an explosion which occurs when groundwater comes into contact with hot lava or magma). A maar characteristically fills with water to form a relatively shallow ...

volcanic crater A volcanic crater is an approximately circular depression in the ground caused by volcanic activity. It is typically a bowl-shaped feature containing one or more vents. During volcanic eruptions, molten magma and volcanic gases rise from an ...

, located west of the Franklin Mountains of

El Paso, Texas El Paso (; ; or ) is a city in and the county seat of El Paso County, Texas, United States. The 2020 United States census, 2020 population of the city from the United States Census Bureau, U.S. Census Bureau was 678,815, making it the List of ...

, in the Potrillo volcanic field of

Doña Ana County, New Mexico Doña Ana County () is a county located in the southern part of the New Mexico, United States. As of the 2020 U.S. Census, its population was 219,561, which makes it the second-most populated county in New Mexico. Its county seat is Las Cruce ...

. Another maar, Hunt's Hole, lies just south. Kilbourne Hole is notable for the large number of mantle

xenolith A xenolith ("foreign rock") is a rock (geology), rock fragment (Country rock (geology), country rock) that becomes enveloped in a larger rock during the latter's development and solidification. In geology, the term ''xenolith'' is almost exclusi ...

s (solid fragments of mantle rock) that were carried to the surface by the eruption. Estimates of the age of the crater vary from about 24,000 to about 80,000 years. In 1975, Kilbourne Hole was designated as a National Natural Landmark by the National Park Service. It is now part of

Organ Mountains–Desert Peaks National Monument The Organ Mountains–Desert Peaks National Monument is a United States national monument in the state of New Mexico, managed by the Bureau of Land Management as part of the National Landscape Conservation System. Description The monument i ...

Geologic setting and formation

Kilbourne Hole and Hunt's Hole are found in the central part of the Potrillo volcanic field, which also contains the Afton-Aden

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 ...

flows. The area is part of the

Rio Grande rift The Rio Grande rift is a north-trending continental rift zone. It separates the Colorado Plateau in the west from the interior of the North American craton on the east. The rift extends from central Colorado in the north to the state of Chihuah ...

, where the

Earth's crust Earth's crust is its thick outer shell of rock, referring to less than one percent of the planet's radius and volume. It is the top component of the lithosphere, a solidified division of Earth's layers that includes the crust and the upper ...

is being stretched and thinned. The rift is characterized by deep

sedimentary basin Sedimentary basins are region-scale depressions of the Earth's crust where subsidence has occurred and a thick sequence of sediments have accumulated to form a large three-dimensional body of sedimentary rock They form when long-term subsidence ...

s, recent faulting and volcanic activity, and unusually high heat flow upwards from the

Earth's mantle Earth's mantle is a layer of silicate mineral, silicate rock between the Earth's crust, crust and the Earth's outer core, outer core. It has a mass of and makes up 67% of the mass of Earth. It has a thickness of making up about 46% of Earth's ...

. Kilbourne Hole and Hunt's Hole are located on the same north-trending fault of the Fitzgerald-Robledo fault system. A

forms when rising

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...

encounters sediment beds saturated with

groundwater Groundwater is the water present beneath Earth's surface in rock and Pore space in soil, soil pore spaces and in the fractures of stratum, rock formations. About 30 percent of all readily available fresh water in the world is groundwater. A unit ...

. The magma heats the groundwater to the point where the

vapor pressure Vapor pressure or equilibrium vapor pressure is the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in a closed system. The equilibrium vapor pressure is an indicat ...

overcomes the weight of the overlying beds (the

overburden pressure Pressure is force magnitude applied over an area. Overburden pressure is a geology term that denotes the pressure caused by the weight of the overlying layers of material at a specific depth under the earth's surface. Overburden pressure is also ca ...

) and the beds are catastrophically blown out.

Country rock Country rock is a music genre that fuses rock and country. It was developed by rock musicians who began to record country-flavored records in the late 1960s and early 1970s. These musicians recorded rock records using country themes, vocal sty ...

is fragmented and expelled into the atmosphere together with fragments of the

, creating a deep crater, the bottom of which sits below the pre-eruptive ground surface. The eruption that is attributed with the formation of the maar depression was dated to around 20,000 years. As a result of the eruption, the maar also experienced a collapse similar to that of a

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the str ...

. Kilbourne Hole erupted through

alluvium Alluvium (, ) is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluvium is also sometimes called alluvial deposit. Alluvium is ...

(unconsolidated water-deposited sediments), the

Camp Rice Formation The Camp Rice Formation is a geologic formation in west Texas and southern New Mexico. It preserves fossils of the Pliocene-Pleistocene. These include the distinctive Tonuco Mountain Local Fauna. Description The formation consists of poorly cem ...

and through the pre-existing Afton basalt flow. Like most maars, it has a shallow rim, composed of erupted material that was deposited as thin

pyroclastic surge A pyroclastic surge is a fluidised mass of turbulent gas and rock fragments that is ejected during some volcanic eruptions. It is similar to a pyroclastic flow but it has a lower density or contains a much higher ratio of gas to rock, which makes i ...

deposits.

Characteristics

The crater is at an elevation of . It has a diameter of and a depth of .2016 National Land Cover (NLCD) dataset
Kilbourne Hole The hole is over a mile wide, and over deep, with crumbling cliffs all around except at the southwest corner. The rim cliffs, measuring about in height, are composed of

and exhibit clear

columnar jointing Columnar jointing is a geological structure where sets of intersecting closely spaced fractures, referred to as Joint (geology), joints, result in the formation of a regular array of polygonal Prism (geometry), prisms, or columns. Columnar join ...

(a feature common to many basalt cliffs, including those of

Devils Postpile National Monument A devil is the personification of evil as it is conceived in many and various cultures and religious traditions. Devil or Devils may also refer to: * Satan * Devil in Christianity * Demon * Folk devil Art, entertainment, and media Film and ...

near

Yosemite National Park Yosemite National Park ( ) is a List of national parks of the United States, national park of the United States in California. It is bordered on the southeast by Sierra National Forest and on the northwest by Stanislaus National Forest. The p ...

and

Moses Coulee Moses Coulee is a canyon in the Waterville plateau region of Douglas County, Washington. Moses Coulee is the second-largest and westernmost canyon of the Channeled Scablands, located about to the west of the larger Grand Coulee. This water chann ...

in the

Channeled Scablands The Channeled Scablands are a relatively barren and soil-free region of interconnected relict and dry flood channels, coulees and cataracts eroded into Palouse loess and the typically flat-lying basalt flows that remain after cataclysmic floods ...

Washington Washington most commonly refers to: * George Washington (1732–1799), the first president of the United States * Washington (state), a state in the Pacific Northwest of the United States * Washington, D.C., the capital of the United States ** A ...

), with characteristic reddish-purple, polygonal (mostly

hexagonal In geometry, a hexagon (from Greek , , meaning "six", and , , meaning "corner, angle") is a six-sided polygon. The total of the internal angles of any simple (non-self-intersecting) hexagon is 720°. Regular hexagon A regular hexagon is d ...

) columns. The base of the cliffs is obscured by

scree Scree is a collection of broken rock fragments at the base of a cliff or other steep rocky mass that has accumulated through periodic rockfall. Landforms associated with these materials are often called talus deposits. The term ''scree'' is ap ...

composed of blocks of basalt that have been dislodged from the columns above by the work of

erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...

and

mechanical weathering Weathering is the deterioration of rocks, soils and minerals (as well as wood and artificial materials) through contact with water, atmospheric gases, sunlight, and biological organisms. It occurs ''in situ'' (on-site, with little or no movem ...

. The basalt

flow Flow may refer to: Science and technology * Fluid flow, the motion of a gas or liquid * Flow (geomorphology), a type of mass wasting or slope movement in geomorphology * Flow (mathematics), a group action of the real numbers on a set * Flow (psyc ...

that comprises these columns

pinches out Pinches is the surname of the following people: * Barry Pinches (born 1970), English snooker player * Jennifer Pinches (born 1994), British artistic gymnast *John Pinches John Harvey Pinches (9 April 1916 – 2 July 2007) was an English rowing ...

(thins) and eventually disappears as it approaches the southwestern rim of the maar. Dropstone at Kilbourne Hole

The eastern and northern rim of the hole have low rim deposits of ejecta from the maar eruptions. These rest on the basalt flow where it is present or on older sediments. The ejecta at Kilbourne Hole contains dropstones launched as

bombs A bomb is an explosive weapon that uses the Exothermic process, exothermic reaction of an explosive material to provide an extremely sudden and violent release of energy. Detonations inflict damage principally through ground- and atmosphere-tra ...

, usually greater than 2.5 inches across and a large number of

s derived from the lower crust and mantle. These have been closely studied by geologists to learn more about geologic processes deep underground. Hunt's Hole is a little smaller, with basalt cliffs only at the northeast and southeast sides of the crater. Layers of ashfall and crumbling

sediment Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...

also rise about high, on the south rim of the crater. Sand dunes have collected on the east sides of both craters, rising about above the desert floor. A dry lakebed lies on the floor of each crater.

Xenoliths

Kilbourne Hole is notable for the abundance of xenoliths in the crater ejecta. These are fragments of country rock carried intact to the surface by the eruption. Xenoliths at Kilbourne Hole include both upper mantle rocks and lower crustal rocks and are most abundant in the northern and eastern rim. Because these are samples of portions of the Earth that are inaccessible by mining or drilling, they are of great scientific interest. Most of the mantle xenoliths at Kilbourne Hole are composed of

lherzolite Lherzolite is a type of ultramafic igneous rock. It is a coarse-grained rock consisting of 40 to 90% olivine along with significant orthopyroxene and lesser amounts of calcic chromium-rich clinopyroxene. Minor minerals include chromium and alumi ...

, a rock composed mostly of

olivine The mineral olivine () is a magnesium iron Silicate minerals, silicate with the chemical formula . It is a type of Nesosilicates, nesosilicate or orthosilicate. The primary component of the Earth's upper mantle (Earth), upper mantle, it is a com ...

and

pyroxene The pyroxenes (commonly abbreviated Px) are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents ions of calcium (Ca), sodium (Na), iron ( ...

. The olivine has a distinctive pale green color in which the pyroxene forms black flecks. Wehrlite is occasionally found here as well. Deep crustal rocks include a variety of

granulite Granulites are a class of high-grade metamorphic rocks of the granulite facies that have experienced high-temperature and moderate-pressure metamorphism. They are medium to coarse–grained and mainly composed of feldspars sometimes associated ...

s of both high-silica (

felsic In geology, felsic is a grammatical modifier, modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz.Marshak, Stephen, 2009, ''Essentials of Geology,'' W. W. Norton & Company, 3rd ed. It is contrasted ...

) and low-silica (

mafic A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks include ...

) compositions, mostly

charnockite Charnockite () is any orthopyroxene-bearing quartz-feldspar rock formed at high temperature and pressure, commonly found in granulite facies’ metamorphic regions, ''sensu stricto'' as an endmember of the charnockite series. Charnockite seri ...

and

anorthosite Anorthosite () is a phaneritic, intrusive rock, intrusive igneous rock characterized by its composition: mostly plagioclase feldspar (90–100%), with a minimal mafic component (0–10%). Pyroxene, ilmenite, magnetite, and olivine are the mafic ...

. These likely took less than three days to reach the surface from their place of origin, and show pristine composition and texture. Their characteristics show that they were little altered from their formation 1.6 to 1.8 billion years ago, other than some reheating during the opening of the Rio Grande rift. Xenoliths are almost entirely absent in the ejecta from Hunt's Hole, but xenoliths are found in Potrillo maar to the south. File:Kilbourne Hole embedded xenolith.jpg, Mantle xenolith embedded in basalt File:Kilbourne Hole lxenoliths.jpg, Mantle xenoliths File:Kilbourne Hole lower crust xenolith.jpg, Lower crust xenolith

NASA training

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 ...

geologically trained the

Apollo Astronauts As part of the Apollo program by NASA, 24 astronauts flew nine missions to the Moon between December 1968 and December 1972. During six successful two-man landing missions, twelve men walked on the lunar surface, six of whom drove Lunar Roving ...

in April and November 1969, June 1970, and January and December 1971. Astronauts who would use this training on the Moon included

Apollo 12 Apollo 12 (November 14–24, 1969) was the sixth crewed flight in the United States Apollo program and the second to land on the Moon. It was launched on November 14, 1969, by NASA from the Kennedy Space Center in Florida. Commander Charles ...

Pete Conrad Charles "Pete" Conrad Jr. (June 2, 1930 – July 8, 1999) was an American NASA astronaut, aeronautical engineer, naval officer, aviator, and test pilot who commanded the Apollo 12 mission, on which he became the third person to walk on t ...

and

Alan Bean Alan LaVern Bean (March 15, 1932 – May 26, 2018) was an American naval officer and aviator, aeronautical engineer, test pilot, NASA astronaut and painter. He was selected to become an astronaut by NASA in 1963 as part of Astronaut Grou ...

Apollo 14 Apollo 14 (January 31February 9, 1971) was the eighth crewed mission in the United States Apollo program, the third to Moon landing, land on the Moon, and the first to land in the Geology of the Moon#Highlands, lunar highlands. It was the las ...

Alan Shepard Alan Bartlett Shepard Jr. (November 18, 1923 – July 21, 1998) was an American astronaut. In 1961, he became the second person and the first American to travel into space and, in 1971, he became the List of Apollo astronauts#Apollo astr ...

and

Edgar Mitchell Edgar Dean "Ed" Mitchell (September 17, 1930 – February 4, 2016) was a United States Navy officer and United States Naval Aviator, aviator, test pilot, Aerospace engineering, aeronautical engineer, Ufology, ufologist, and NASA astronaut. ...

Apollo 15 Apollo 15 (July 26August 7, 1971) was the ninth crewed mission in the Apollo program and the fourth Moon landing. It was the first List of Apollo missions#Alphabetical mission types, J mission, with a longer stay on the Moon and a greate ...

David Scott David Randolph Scott (born June 6, 1932) is an American retired test pilot and NASA astronaut who was the List of Apollo astronauts#People who have walked on the Moon, seventh person to walk on the Moon. Selected as part of the NASA Astronaut ...

and

James Irwin James Benson Irwin (March 17, 1930 – August 8, 1991) was an American astronaut, aeronautical engineer, test pilot, and a United States Air Force Aviator, pilot. He served as Lunar Module pilot for Apollo 15, the fourth human lunar landin ...

Apollo 16 Apollo 16 (April 1627, 1972) was the tenth human spaceflight, crewed mission in the United States Apollo program, Apollo space program, administered by NASA, and the fifth and penultimate to Moon landing, land on the Moon. It was the second o ...

's John Young and Charlie Duke, and

Apollo 17 Apollo 17 (December 7–19, 1972) was the eleventh and final mission of NASA's Apollo program, the sixth and most recent time humans have set foot on the Moon. Commander Gene Cernan and Lunar Module Pilot Harrison Schmitt walked on the Moon, ...

Gene Cernan Eugene Andrew Cernan (; March 14, 1934 – January 16, 2017) was an American astronaut, naval aviator, electrical engineer, aeronautical engineer, and fighter pilot. Cernan traveled into space three times and to the Moon twice: as pilot ...

and

Jack Schmitt Harrison Hagan "Jack" Schmitt (born July 3, 1935) is an American geologist, former NASA astronaut, university professor, former U.S. senator from New Mexico. He is the most recent living person—and only person without a background in military a ...

. In 2017, a NASA field team visited the hole to test various instruments that are planned to be used in future space missions. Jack Schmitt attended the tests, as well as astronaut Barry Wilmore who was there to assist in simulated moonwalks at the hole.

Access

Kilbourne Hole is located within

and administered by the

Bureau of Land Management The Bureau of Land Management (BLM) is an agency within the United States Department of the Interior responsible for administering federal lands, U.S. federal lands. Headquartered in Washington, D.C., the BLM oversees more than of land, or one ...

. It is accessed via Doña Ana County Road A-011, driving west from the railroad. The hole is "on the right, past the big tan dirt bank." Much of the land inside the hole is private property, and collecting rocks from the location is illegal. Hunt's Hole is about south on A-013.

Geologic setting and formation

Characteristics

Xenoliths

NASA training

Access

See also

References

Further Reading