The Plains of San Agustin (sometimes listed as the Plains of San Augustin) is a region in the southwestern

U.S. state In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its so ...

New Mexico New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...

in the ''San Agustin Basin,'' south of U.S. Highway 60. The area spans Catron and Socorro Counties, about west of the town of Socorro and about north of Reserve. The plains extend roughly northeast-southwest, with a length of about 55 miles (88 km) and a width varying between 5–15 miles (8–24 km). The basin is bounded on the south by the Luera Mountains and Pelona Mountain (outliers of the

Black Range The Black Range (also called the Devil's Mountains or Sierra Diablo) is an igneous mountain range running north–south in Sierra, Grant, and Catron counties in southwest New Mexico, in the Southwestern United States. Description The range's ...

); on the west by the Tularosa Mountains; on the north by the

Mangas Manges (; Greek: μάγκες ; sing.: mangas , μάγκας ) is the name of a social group in the Belle Époque era's counterculture of Greece (especially of the great urban centers of Athens and Piraeus). The nearest English equivalent to the t ...

, Crosby, Datil, and Gallinas Mountains; and on the east by the San Mateo Mountains. The

Continental Divide A continental divide is a drainage divide on a continent such that the drainage basin on one side of the divide feeds into one ocean or sea, and the basin on the other side either feeds into a different ocean or sea, or else is endorheic, not ...

lies close to much of the southern and western boundaries of the plains.''New Mexico Atlas and Gazetteer'', Second Edition, DeLorme Mapping, 2000.

Geology

Geologically, the Plains of San Agustin lie within the Mogollon-Datil volcanic field, just south of the southeast edge 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 ...

, and west 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 ...

Valley. The basin is a

graben In geology, a graben () is a depression (geology), depressed block of the Crust (geology), crust of a planet or moon, bordered by parallel normal faults. Etymology ''Graben'' is a loan word from German language, German, meaning 'ditch' or 't ...

(a downdropped block which subsided between parallel faults). The graben is younger than the Datil-Mogollon volcanic eruptions.Stearns, Charles E. (1962) ''Geology of the north half of the Pelona Quadrangle, Catron County, New Mexico'' Bulletin 78, New Mexico Bureau of Mines and Mineral Resources, Socorro, NM, The flat floor of the plains was created by a

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

lake ( Lake San Agustin).Halka Chronic, ''Roadside Geology of New Mexico'', Mountain Press Publishing, Missoula, 1987, . Although the graben has dropped an estimated , the surface relief has been reduced to about by sedimentation. A great deal of the sediments entered the San Agustin basin prior to the formation of Lake San Agustin in the last glacial period. There is no evidence of tectonic activity in the area after Lake San Agustin became extinct. Hydrologically, the plains contain the terminal playas for the San Agustin Basin, an

endorheic basin An endorheic basin ( ; also endoreic basin and endorreic basin) is a drainage basin that normally retains water and allows no outflow to other external bodies of water (e.g. rivers and oceans); instead, the water drainage flows into permanent ...

straddling the

. The catchment area of the basin covers an approximate of land in the surrounding area. Ecologically, the plains lie near the northern end of the Chihuahuan Desert (though the ranges surrounding the

Gila River The Gila River (; O'odham ima Keli Akimel or simply Akimel, Quechan: Haa Siʼil, Maricopa language: Xiil) is a tributary of the Colorado River flowing through New Mexico and Arizona in the United States. The river drains an arid watershed of ...

headwaters intervene), which is dominated by

shrubland Shrubland, scrubland, scrub, brush, or bush is a plant community characterized by vegetation dominance (ecology), dominated by shrubs, often also including grasses, herbaceous plant, herbs, and geophytes. Shrubland may either occur naturally o ...

Climate

The Plains of San Agustin has a

cold semi-arid climate Cold is the presence of low temperature, especially in the atmosphere. In common usage, cold is often a subjective perception. A lower bound to temperature is absolute zero, defined as 0.00K on the Kelvin scale, an absolute thermodynamic ...

( ''BSk'').

Landmarks

The plains are probably best known as the site of the

Very Large Array The Karl G. Jansky Very Large Array (VLA) is a centimeter-wavelength radio astronomy observatory in the southwestern United States built in the 1970s. It lies in central New Mexico on the Plains of San Agustin, between the towns of Magdalena, Ne ...

, a

radio astronomy Radio astronomy is a subfield of astronomy that studies Astronomical object, celestial objects using radio waves. It started in 1933, when Karl Jansky at Bell Telephone Laboratories reported radiation coming from the Milky Way. Subsequent observat ...

observatory An observatory is a location used for observing terrestrial, marine, or celestial events. Astronomy, climatology/meteorology, geophysics, oceanography and volcanology are examples of disciplines for which observatories have been constructed. Th ...

. The plains were chosen for the observatory because of their isolated location away from large population centers, and the partial shielding effect of the surrounding mountain ranges. The edges of the plains have sites of

archaeological Archaeology or archeology is the study of human activity through the recovery and analysis of material culture. The archaeological record consists of Artifact (archaeology), artifacts, architecture, biofact (archaeology), biofacts or ecofacts, ...

interest such as a prehistoric rockshelter known as Bat Cave. Other sites in the area include a ghost town called Old Horse Springs and the Ake Site, a prehistoric occupation site.

Notes

Sources

* Powers, William E. (1939) "Basin and Shore Features of the Extinct Lake, San Augustin, New Mexico" ''Journal of Geomorphology'' 2: pp. 345–356 * Weber, Robert H. (1994) "Pluvial Lakes of the Plains of San Augustin" ''In'' Chamberlin, R.M. ''et al.'' (1994) ''Mogollon Slope, West-Central New Mexico and East-Central Arizona'' pp. 9–11, New Mexico Geological Society, Forty-Fifth Annual Field Conference, Socorro, New Mexico.
Holliday, Vance T. 'et al.'' (2007) "Paleoindian Geoarchaeology and the Archaeological Potential on the Plains of San Augustin, New Mexico" Argonaut Archaeological Research Fund, Department of Anthropology and Department of Geosciences, University of Arizona, Tucson, Arizona, USA

External links

* {{coord, 33, 52, 31, N, 108, 15, 03, W, display=title Landforms of Catron County, New Mexico Great Divide of North America Landforms of New Mexico Landforms of Socorro County, New Mexico Plains of the United States