The Gran Desierto de Altar is one of the main sub-ecoregions of the Sonoran Desert, located in the State of Sonora, Northwest Mexico. This includes the only region of erg mounds active in North America. The desert extends across most of the northern border of the Gulf of California, reaching over 100 kilometers (62 miles) east to west, and more than 50 kilometers (31 miles) north to south. It is the largest continuous desert area in the Sonoran Desert.
The eastern part of this area contains the Pinakata volcano area, and with the western area of ​​Gran Desierto de Altar, together they form the Gran Desierto de Altar Reservoir of El Pinacate y and the UNESCO World Heritage Site.
Video Gran Desierto de Altar
Geography
Gran Desierto covers about 5,700 square kilometers (2,200 sq. Million), mostly in the state of Sonora, Mexico. The northern end of the border overlaps the Organ Pipe Cactus National Monument and Cabeza Prieta National Wildlife Reserve in southwest Arizona. The dominant sand and dune layers have a thickness of less than 1 kilometer (0.62 miles) to more than 12 kilometers (7.5 mi). The total volume of sand at Gran Desierto is about 60 cubic km. Most of the volume was delivered by the Colorado River Pleistocene that flows through the Gran Desierto area now ~ 120,000 years before now. The Pleistocene Delta migrates westward along with the breaking fault and rifting associated with the opening of Salton Trough and the Gulf of California.
Maps Gran Desierto de Altar
Physiography
The eastern edge of Gran Desierto borders the Cenozoikum volcano complex of Sierra Pinacate, a composite volcanic field that covers over 1,800 kilometers (1,100 mi) of 2 with a peak of 1,206 meters (3,957Ã, ft). Aeolian sand has risen to many slopes west of Sierras Pinacate, defining the eastern boundary of the sand dunes. In the north, thin sand thins to the distal edge of alluvial fans from Tinajas Altas and the Tule Mountains along the Arizona-Sonora border. The southern boundary of the sand sea is the northern coast of California Bay.
The southern most extension of the San Andreas Fault crosses the area and lies beneath some prominent granite inselberg, especially the Sierra del Rosario mountains surrounded by erg on all sides. The Sierra Enternada is a smaller inselberg almost completely buried by sand near the border of Gran Desierto and the Pinacate volcanic complex.
Sand sand distribution
Gran Desierto is famous for its incredible star Dunes, many of which are over 100 meters (330 feet tall). More than two thirds of Gran Desierto is covered by sand sheets and sand stripes. The remaining area is divided equally between the population of the western hills of a star and a set of eastern hills or crescent hills. Some of the larger crescent sands in the sea of ​​northeast sand show upside down cliffs, transitional morphological features associated with stellar hills.
Flora
The vegetation collection of Gran Desierto is typical of the lower Sonoran Desert with striking differences in vegetation type and density with location. The vast areas of the southern and eastern sand seas, especially near the periphery, have a fairly dense cover (up to 20%) of shrubs and low perennial shrubs such as bursage (Ambrosia dumosa) and longleaf jointfir ( Ephedra trifurca ) with creosote shrubs ( Larrea tridentata ) in thin sand cover areas. The Palo verde/acacia/ocotillo community takes place on the alluvial slope on the north side of the sand ocean, especially in arroyos and washing. It is estimated that the total vegetation cover reaches 15% in star hills and about 10% in low or crescentic sand dune areas. This percentage is much larger than in most active mounds where vegetation cover is 15% more typical.
Several teams have examined the nests (middens) built by mice as a proxy for the ancient vegetation regime. All have concluded that Gran Desierto has been a refugia for desert plants since at least the end of the Pleistocene. Gran Desierto has served as a refuge for the most dominant Mojave Desert plant species during the cold pluvial period as well. The C14 date for the embankment of the Tinajas Altas Mountains showing juniper trees and Joshua trees coexist with contemporary Gran Desierto flora and fauna more than 43,000 years before this time. Although muddy studies do not provide information beyond the final Pleistocene, they show that, in rough form, the Gran Desierto climate as noted by the plant community has become like a desert at least since the peak of Wisconsinan glaciers.
Fauna
- See the article on: Sonora Desert Fauna
Climate
Gran Desierto has a warm, dry climate. The average annual rainfall, mostly occurring between September and December, is 73 mm in Puerto PeÃÆ'Â ± asco, Sonora (located on the southeast bank of sand) and descends northwards to Yuma, Arizona (on the northwestern edge) to 62 mm per year. The mid-summer highs exceed 45 Â ° C is common in the central sand sea. Mid-winter lows less than 10 Ã, Â ° C is rare. The wind is controlled in part by the position and strength of Sonoran Low in the summer, creating a southerly wind, and by Great Basin High in winter, with north winds to the northeast.
Paleoclimate
The well-documented pluvial period occurring in most of the southwestern United States during the most recent ice age (Wisconsin) may not extend as far south as Gran Desierto. It seems that the climate regime of the last 150,000 years on this site has been one of the gradually increasing degenerates with the present-day hyperaricities that were strongly existing at least 43,000 years ago.
At a minimum, it can be assumed that the coastal ground breeze from the south is less important for sand movement when the Wisconsin coastline is 45 km to the ocean from its current position.
Tectonic
Gran Desierto is located adjacent to the rapidly subsiding tectonic basin, Salton Trough, which is a northern extension of the Gulf of California, an embayment created by rifting that began during Pliocene along the East Pacific Rise and San Andreas fault system. Regional subsidence has spread to the northwest clutter and horizontal fault continues to this day. The central part of the nearby Salton Trough is over 70 meters (230Ã, ft) below sea level; it is protected from sea embayment only with a natural embankment from the Colorado River Delta.
Ongoing tectonic activity modifies Gran Desierto today. The southern extension of the San Andreas fault system, Cerro Prieto Fault, passes directly through the area before proceeding offshore into the Gulf of California. The strike-slip movement in this area is as high as 60 mm/year.
Since 1900, a magnitude of 6.3 and two large-scale 7.1 earthquakes came from erg. Most of the seismicity in Gran Desierto comes from a depth of five to six kilometers, corresponding to the transition between delta deposits and basement crystal rocks. Local appointments still occur along Mesa Arenosa, a multiple fault block that forms coastal boundaries.
Origin
Gran Desierto's geological history is closely related to the opening of the Gulf of California and the capture of the ancestral Colorado River; the source area adjacent to Gran Desierto has shifted in position, the underground topography has been altered continuously, and the bedform has been made, modified or completely destroyed and then reworked.
The Gran Desierto sandbags and sand dunes are located above the sediments of the Pleistocene Colorado delta. The lower Colorado River was captured by the Gulf of California 1.2 million years before now. This event places an upper limit on Gran Desierto's age with a major source of clastic sediment in Colorado. The sand of konglomerit and mud under Mesa Arenosa was examined by Colletta and Ortlieb and dated between 700,000 and 120,000 years before now.
The vertebrate fossils found by Merriam in delta deposits include Equus, Gomphotherium and Bison and assigned to Irvingtonian ages (0.5 to 1.8 million years before present); a date consistent with the catching of the lower Colorado River above. Evidence of the giant pangolin Myrmecophaga tridactyla is found in the delta deposit at Gran Desierto south. Van Devender noted that the specimens were found to be related to fossil mammoths, sloths and boa constrictors; a collection of tropical fauna that supports the assumption that the Colorado River delta from the previous interglacial period (& gt; 120,000 years ago) is much warmer and wetter than the current interglacial.
The paleo-delta sediment near Salina Grande correlates with ubiquitated induced skin deposits transmitted by the radiometric Io/U method at 146,000 13,000/-11,000 years. Slate earns K-Ar age for basal flow in western Pinacates. Based on this work, some aeolian activities may have been present as early as 700,000 years ago, as evidenced by the accretionary coats dated on the basal flow of the Pinacate volcanic plane.
Blount and Lancaster propose that at the time of the late Pleistocene, the Colorado River is a very competent stream that flows through the area occupied today by the enormous zone of western star mounds. The beach is currently at least 45 kilometers (28 miles) south of its current location. The primary base load of poorly ordered pebbles is deposited from Yuma, Arizona now to the southern regions of the Sierra del Rosario mountains today.
When California Gulf rifting develops to the northwest, and lifting along the coast begins, the river channel shifts westward, leaving behind the primary bedload beds in the former channels and floodplains. The Delta sediments under Gran Desierto can reach a depth of 6,000 kilometers (3,700 miles).
The annual sediment load before the Colorado River dam was so remarkable. A flood event deposits about 100,000,000 m 3 from coarse sand to medium as a deposit sheet in the modern delta just south of the international boundary. Events like this, even if rarely, can fill Gran Desierto in just a few millennia.
Offshore features
The synchronous development of the Colorado River Delta and Gran Desierto sands sinks offshore into the Gulf of California. The report on the topography of the submarine of the Gulf of California by van Andel, describes three previous river channels on the seafloor: originating from the current Colorado delta, another from the delta-paleo area between El Golfo and Salina Grande, and a third to the current Puerto Penasco. Rusnak reports on sonar soundings that find the valley and also depicts two longitudinal depressions, each about 40 kilometers (25 miles) long, where the valley network ends at a depth of ~ 180 meters (590 feet) below sea level. The incised valley system was also interpreted as the fluvial origin.
See also
- El Pinacate y Gran Desierto de Altar Biosfer Reserve
- Pinacate Peaks
- Sonoran Desert
- Flora from the Sonoran Desert
- Lechuguilla Desert
- Yuma Desert
- Colorado Desert
- Chihuahuan Desert
References
- Biehler, S., Kovach, R.L. and Allen, C.R., Geophysical frameworks from the northern edge of the Gulf of California structural province, in California Marine Bay Geology, van Andel, T.H. and Shor, G.G., eds., A.A.P.G., Memoir 3, 126-143, 1964.
- Guzman, A.E., Possible oil in the Altar Desert, Sonora, Mexico, abs., A.A.P. G., 64, 716, 1980.
- MacDougal, D.T., Across from Papagueria, Bull. American Geographical Soc., 40, 705-725, 1908.
External links
- The World Heritage Center: UNESCO's official website El Pinacate and Gran Desierto de Altar Biosfer Reserve
- UNESCO: Backup photo gallery
- ElPinacate.gob.mx: Reserva de la Biosfera El Pinacate y Gran Desierto de Altar
- ElPinacate.gob.mx: "Historia" (la ocupaciÃÆ'³n humana)
Source of the article : Wikipedia
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