Kilbourne Hole: Difference between revisions

[[File:Kilbourne and Hunts Holes and White Sands.jpg|thumb|Kilbourne Hole (center) and Hunt's Hole (lower right), with [[White Sands National Park]] lit by the sun in the distance beyond the [[Organ Mountains]].]]

'''Kilbourne Hole''' is a [[maar]] [[volcanic crater]], located {{convert|30|mi|km}} west of the [[Franklin Mountains (Texas)|Franklin Mountains]] of [[El Paso, Texas]], in the [[Potrillo volcanic field]] of [[Doña Ana County, New Mexico]]. Another maar, Hunt's Hole, lies just two miles{{Convert|2|mi|km|spell=in}} south of Kilbourne Hole. Kilbourne Hole is notable for the large number of [[Earth's mantle|mantle]] [[xenolith]]s, (solid fragments of mantle rock,) that were carried to the surface by the eruption.

Kilbourne Hole and Hunt's Hole are found in the central part of the [[Potrillo volcanic field]], which also contains the Afton-Aden [[basalt]] flows. The area is part of the [[Rio Grande rift]], where the [[Earth's crust]] is being stretched and thinned. The rift is characterized by deep [[sedimentary basin]]s, recent faulting and volcanic activity, and unusually high heat flow upwards from the [[Earth's mantle]]. Kilbourne Hole and Hunt's Hole are located on the same north-trending fault of the Fitzgerald-Robledo fault system.<ref name="padovani-reid-1989">{{cite journal |last1=Padovani |first1=Elaine R. |last2=Reid |first2=Mary R. |title=Field guide to Kilbourne Hole maar, Dona Ana County, New Mexico |journal=New Mexico Bureau of Mines and Mineral Resources Memoir |date=1989 |volume=46 |pages=174–185 |url=https://geoinfo.nmt.edu/publications/monographs/memoirs/46/ |access-date=22 March 2022}}</ref>

A [[maar]] forms when rising [[magma]] encounters sediment beds saturated with [[groundwater]]. The magma heats the groundwater to the point where the [[vapor pressure]] overcomes the weight of the overlying beds (the [[overburden pressure]]) and the beds are catastrophically blown out. [[Country rock (geology)|Country rock]] is fragmented and expelled into the atmosphere together with fragments of the [[magma]], creating a deep crater, the bottom of which sits below the pre-eruptive ground surface.<ref name="schmincke-2203-209-228">{{cite book |last1=Schmincke |first1=Hans-Ulrich |title=Volcanism |date=2003 |publisher=Springer |location=Berlin |isbn=9783540436508 |pages=209–228}}</ref> The eruption that is attributed with the formation of the maar depression was dated to around 20,000 years.<ref>{{Cite journal |last=Perkins |first=Dexter |last2=Anthony |first2=Elizabeth Y. |date=2011-12-01 |title=The evolution of spinel lherzolite xenoliths and the nature of the mantle at Kilbourne Hole, New Mexico |url=https://link.springer.com/article/10.1007/s00410-011-0644-1 |journal=Contributions to Mineralogy and Petrology |language=en |volume=162 |issue=6 |pages=1139–1157 |doi=10.1007/s00410-011-0644-1 |issn=1432-0967}}</ref> As a result of the eruption, the maar also experienced a collapse similar to that of a [[caldera]].<ref>{{Cite web |title=New Mexico Geology: Abstract |url=https://geoinfo.nmt.edu/publications/periodicals/nmg/details.cfml?id=28291 |access-date=2024-10-25 |website=New Mexico Bureau of Geology & Mineral Resources |language=en |doi=10.58799/nmg-v9n4.69}}</ref>

Kilbourne Hole erupted through [[alluvium]] (unconsolidated water-deposited sediments), the [[Camp Rice Formation]] and through athe pre-existing thinAfton basalt flow. Like most maars, it has a shallow rim, composed of erupted material that was deposited as thin [[pyroclastic surge]] deposits.<ref name="padovani-reid-1989"/>

The crater is at an elevation of {{convert|4239|ft|abbr=on}}. It has a diameter of {{convert|1.5|mi|abbr=on}} by {{convert|2.1|mi||abbr=on}} and a depth of {{convert|443|ft|abbr=on}}.<ref name = nlcd2016 >[https://viewer.nationalmap.gov/advanced-viewer/viewer/index.html?marker=-106.964722,31.971944,4326,from%20Kilbourne_Hole,,Kilbourne%20Hole&scale=10000 2016 National Land Cover (NLCD) dataset] Kilbourne Hole</ref>

The hole is over a mile wide, and over {{convert|300|ft|m}} deep, with crumbling [[basalt]] cliffs all around except at the southwest corner. The basaltrim cliffs, resemblemeasuring theabout cliffs{{convert|40|ft|m}} in height, are composed of the[[basalt]] and exhibit clear [[columnar jointing]] (a feature common to many basalt cliffs, including those of [[Devils Postpile National Monument]] near [[Yosemite National Park]], withand [[Moses Coulee]] in the characteristic[[Channeled reddishScablands]] purpleof hexagonal[[Washington columns(state)|Washington]]), exceptwith thatcharacteristic theyreddish-purple, arepolygonal not(mostly as[[Hexagonal_prism|hexagonal]]) tallcolumns. The base of the cliffs areis aboutobscured {{convert|40|ft|m}}by high.[[scree]] composed Theof baseblocks of basalt that have been dislodged from the cliffscolumns isabove coveredby withthe awork of [[screeerosion]] ofand basalt[[Weathering#Physical_weathering|mechanical blocksweathering]]. The basalt [[Lava flow|flow]] that comprises these columns [[Pinch-out|pinches out]] (thins) and eventually disappears onas it approaches the southwestern rim of the holemaar.<ref name="padovani-reid-1989"/>

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 [[Volcanic bomb|bombs]], usually greater than 2.5 inches across<ref>{{Cite web |title=Tour: Kilbourne Hole |url=https://geoinfo.nmt.edu/tour/landmarks/kilbourne_hole/ |access-date=2024-10-26 |website=New Mexico Bureau of Geology & Mineral Resources |language=en}}</ref> and a large number of [[xenolith]]s derived from the lower crust and mantle. These have been closely studied by geologists to learn more about geologic processes deep underground.<ref name="padovani-reid-1989"/>

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]] also rise about {{convert|40|ft|m}} high, on the south rim of the crater. Sand dunes have collected on the east sides of the both craters, rising about {{convert|100|ft|m}} above the desert floor. A dry lakebed lies on the floor of each crater.

Most of the mantle xenoliths at Kilbourne Hole are composed of [[lherzolite]], a rock composed mostly of [[olivine]] and [[pyroxene]]. The olivine has a distinctive pale green color in which the pyroxene forms black flecks. [[PeridotiteWehrlite]] is occasionally found here as well.<ref name="padovani-reid-1989"/>

Deep crustal rocks include a variety of [[granulite]]s of both high-silica ([[felsic]]) and low-silica ([[mafic]]) compositions, mostly [[charnockite]] and [[anorthosite]].<ref>{{Cite web |title=Tour: Kilbourne Hole |url=https://geoinfo.nmt.edu/tour/landmarks/kilbourne_hole/ |access-date=2024-10-26 |website=New Mexico Bureau of Geology & Mineral Resources |language=en}}</ref> 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.<ref name="padovani-reid-1989"/>

[[NASA]] geologically trained the [[Apollo Astronauts]] in April and Nov.November 1969, June 1970, and Jan.January and Dec.December 1971. Astronauts who would use this training on the Moon included [[Apollo 12]]'s [[Pete Conrad]] and [[Alan Bean]], [[Apollo 14]]'s [[Alan Shepard]] and [[Edgar Mitchell]], [[Apollo 15]]'s [[David Scott]] and [[James Irwin]], [[Apollo 16]]'s [[John Young (astronaut)|John Young]] and [[Charlie Duke]], and [[Apollo 17]]'s [[Gene Cernan]] and [[Jack Schmitt]].<ref>{{cite book |last1=Phinney |first1=William |title=Science Training History of the Apollo Astronauts |date=2015 |publisher=NASA SP -2015-626 |pages=233, 235, 237, 241, 245, 251}}</ref>

Kilbourne Hole is located within [[Organ Mountains–Desert Peaks National Monument]] and administered by the [[Bureau of Land Management]].<ref name=BLM>{{cite web | url = https://www.blm.gov/visit/kilbourne-hole-volcanic-crater | title = Kilbourne Hole Volcanic Crater | accessdate = 10 September 2020 |publisher=Bureau of Land Management}}</ref> It is accessed via Doña Ana County Road A-011, driving {{Convert|8 miles|mi|km}} west from the railroad. The hole is "on the right, past the big tan dirt bank."<ref name=BLM/> Much of the land inside the hole is private property., and collecting rocks from the location is illegal. Hunt's Hole is about {{Convert|2 miles|mi|km}} south on A-013.

[[File:BLM Sign on the Road to Kilbourne Hole.jpg|thumb|right|BLM sign on the road to Kilbourne Hole.]]