Sierra Madera crater

Sierra Madera Crater
Sierra Madera viewed from US Highway 385
Impact crater/structure
ConfidenceConfirmed[1]
Diameter8 mi (13 km)
Age≲100 million years
ExposedYes
DrilledYes
Location
LocationPecos County, West Texas
Coordinates30°36′N 102°55′W / 30.600°N 102.917°W / 30.600; -102.917[2]
CountryUnited States
Sierra Madera
Sierra Madera in Texas
Topo mapSierra Madera

The Sierra Madera crater is a complex impact crater (astrobleme) in southwestern Pecos County, Texas, United States.[3] The impact structure spans approximately 8 mi (13 km) in diameter and is centered 20 mi (30 km) south of Fort Stockton, roughly equidistant from Mexico and New Mexico and near the northeastern end of the Glass Mountains.[4][5] The central peak of the rebound structure of the impact crater rises 793 ft (242 m) above the surrounding land.[3] The peak is visible from U.S. Highway 385 between Fort Stockton, Texas and Marathon, Texas. The Sierra Madera crater is located on private property on the La Escalera Ranch.

The crater is mostly eroded but remains well exposed.[6] At the center of the crater are the hilly remains of the central peak produced by the impact.[4] Known as Sierra Madera or Madera Mountain, the uplift rises 4,593 ft (1,400 m) above sea level. The peak occupies most of the crater and is its most prominent feature, spanning about 5 mi (8 km) across.[4][5][3] Strongly folded and faulted carbonate and siliciclastic rock layers from the upper Paleozoic to Cretaceous comprise the central structure,[6] along with breccia fragments spanning as much as several meters across.[4] The oldest Permian rocks in the structure lie 3,900 ft (1,200 m) above their typical position.[5] The strata folded in the central uplift provide an indication of the impact's age.[5] An alluvium-filled depression up to 1 mi (1.6 km) wide surrounds the central uplift,[3][6] outlined by an outer concentric crater rim about 0.5 mi (0.80 km) wide.[3] The crater rim consists of low hills that climb subtly above the surrounding land.[5]

The first geological map of the Sierra Madera was published in 1930.[5] The central peak was initially interpreted as a cryptovolcanic structure. However, no igneous rocks were detected within 13,000 ft (4,000 m) of the surface. The discovery of shatter cones, impact breccias, and shocked quartz in the 1960s, along with supporting gravity and magnetic surveys, lent credence to interpreting the structure as having impact origins.[4] The shock-related features identified in rock samples suggest the impact produced pressures of at least 3 to 20 GPa, with erosion masking the record of more intense pressures.[6]

The impact that produced the Sierra Madera likely occurred sometime between the late Cretaceous and early Paleogene (within 100 million years ago) in an area with thick sediment about 3.4 mi (5.5 km) in depth.[4][7] The impact site, at the southern edge of the Val Verde Basin, may have been underwater at the time of impact.[6][8] The surrounding area now is largely flat or rolling shrubland and grassland with sand and caliche.[3] The apparent 8 mi (13 km) diameter of the crater is based on the diameter of the concentric outer hills interpreted as a crater rim.[6] However, studies in the 2000s suggest the structure may be larger than initially thought;[4] one 2006 study estimated a 9.9 mi (16 km) diameter with significant erosion.[7] The entire bowl-shaped impact structure extends to 6,000–8,000 ft (1,800–2,400 m) below the surface.[8]

In the 1960s, the Sierra Madera crater was the subject of various studies conducted by the Astrogeology Research Program at USGS as part of the Apollo program, providing an analogous setting to lunar craters.[9][10][11] Apollo 17's Gene Cernan and Jack Schmitt did some of their geological training here in March 1972.[9]

See also

References

  1. ^ "SierraMadera". Earth Impact Database. Planetary and Space Science Centre University of New Brunswick Fredericton. Retrieved December 10, 2016.
  2. ^ U.S. Geological Survey Geographic Names Information System: Sierra Madera
  3. ^ a b c d e f "Exploring Sierra Madera: A Unique Cryptoexplosion Structure". Handbook of Texas Online. Texas State Historical Association (published 1952). April 1, 1995. Retrieved February 7, 2026.
  4. ^ a b c d e f g Flamini, Enrico; Coletta, Alessandro; Battagliere, Maria Libera; Virelli, Maria (2019). "Sierra Madera, USA". In Flamini, Enrico; Di Martino, Mario; Coletta, Alessandro (eds.). Encyclopedic Atlas of Terrestrial Impact Craters (1st 2019 ed.). Springer International Publishing. pp. 609–611. doi:10.1007/978-3-030-05451-9. ISBN 9783030054496.
  5. ^ a b c d e f Howard, Keith A.; Offield, Terry W.; Wilshire, H. G. (1972). "Structure of Sierra Madera, Texas, as a Guide to Central Peaks of Lunar Craters". Geological Society of America Bulletin. 83 (9). Geological Society of America: 2795. doi:10.1130/0016-7606(1972)83[2795:SOSMTA]2.0.CO;2.
  6. ^ a b c d e f Huson, Sarah; Pope, Michael; Watkinson, A. John; Foit, Franklin (January 1, 2011). "Deformational features and impact-generated breccia from the Sierra Madera impact structure, west Texas". Geological Society of America Bulletin. 123 (1–2). Geological Society of America: 371–383. doi:10.1130/B30183.1.
  7. ^ a b Goldin, Tamara J.; Wünnemann, Kai; Melosh, H. Jay; Collins, Gareth S. (December 2006). "Hydrocode modeling of the Sierra Madera impact structure". Meteoritics & Planetary Science. 41 (12): 1947–1958. doi:10.1111/j.1945-5100.2006.tb00462.x.
  8. ^ a b Wilshire, H. G.; Offield, T. W.; Howard, K. A.; Cummings, David (1972). Geology of the Sierra Madera Cryptoexplosion Structure, Pecos County, Texas (PDF) (Report). Contributions to Astrogeology. Washington, D. C. Retrieved February 6, 2026.
  9. ^ a b Phinney, William (2015). Science Training History of the Apollo Astronauts. NASA SP -2015-626. pp. 251–252.
  10. ^ Wilshire, H. G. (October 1965). "Geology of the Sierra Madera Structure, Texas: Progress Report". Astrogeologic Studies: Annual Progression Report, Part B: Crater Investigations. United States Geological Survey. pp. 1–25. Retrieved February 7, 2026 – via Google Books.
  11. ^ Cantrell, Mary (December 7, 2022). "50th anniversary of Apollo 17: when astronauts came to the Big Bend". The Big Bend Sentinel. Sentinel News Project. Retrieved February 19, 2026.


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