Oct 252016
 

Basalt is a dark, fine-grained, basic (low silica) igneous rock, often extruded as molten lava from volcanic fissures. Its low silica content means it can flow easily, often building up over the years to form large plateaus. As the basaltic lava cools, it contracts and solidifies. An extensive network of cracks often develop in basalt, which may extend many meters deep. These cracks tend to leave columns between them which are roughly hexagonal (6-sided) in shape. Among the more famous examples of basalt columns or pavements in the world are Giant’s Causeway (Northern Ireland), Fingal’s Cave (Scotland) and Devil’s Postpile (California, USA).

The best known location in Mexico to see basalt columns is about an hour’s drive north of Mexico City, at Santa María Regla, in the state of Hidalgo. These columns, attractively located on the side of a canyon, with a waterfall tumbling over some of them (see sketch), were visited by the famous Prussian scientist/geographer Alexander von Humboldt, during his exploration of Mexico in 1803-04. Some individual columns are 40 meters tall.

Basalt prisms at San Miguel Regla

Basalt prisms at San Miguel Regla, from Humboldt and Bonpland, Vues des Cordilleres et monumens des peuples indigenes de l’Amerique.

The basalt columns of Santa María Regla are one of the locations described in The first geography fieldtrip guide in Mexico. They are also one of Mexico’s top 13 natural wonders.

Basalt prisms at Santa María Regla

Other locations in Mexico where basalt columns or prisms can be seen include a quarry between the towns of Jamay and Ocotlán (Jalisco), the south-facing slope of the hills overlooking the town of Chapala (Jalisco) and the Salto (waterfall) de San Antón (Cuernavaca, Morelos).

Mexico’s geology and landforms are analyzed in chapters 2 and 3 of Geo-Mexico: the geography and dynamics of modern Mexico.  Buy your copy of this book today!

Oct 122016
 

As vertical shafts go, this is a seriously deep one! Long considered to be “bottomless” (because no-one had ever managed to find the floor), we now know it is precisely 335 meters (1099 feet) deep, making it the deepest water-filled sinkhole anywhere on the planet.

The El Zacatón sinkhole is on El Rancho Azufrosa, near the town of Aldama in Tamaulipas in northeast Mexico. The sinkhole or cenote is one of several located in the same area, though recent studies have failed to demonstrate any obvious underground connections between them. The term cenote is a Spanish rendering of the Mayan word d’zonot, “a hole in the ground”. The El Zacatón pit, which is about 110 meters (360 feet) across and roughly circular, contains a deep lake. The water is warm (averaging about 30 degrees C), highly mineralized and has a sulfurous odor. The name El Zacatón comes from the floating islands of grass (zacate) which blow across this lake from one side to the other with the wind.

The Zacatón Sinkhole

The Zacatón Sinkhole

The pit’s depth has attracted serious divers for many years. In 1993, Dr. Ann Kristovich dove to a new women’s world record depth of 169 meters (554 feet). The following year, two American explorers tried to reach the bottom of the sinkhole. Jim Bowden successfully reached a men’s world record depth of 282 meters (925 feet) but still did not touch the bottom. Tragically, his diving partner Sheck Exley died during the attempt.

The mystery of the sinkhole’s depth was finally solved in 2007. A multi-million dollar exploration, mainly funded by NASA, trialled the Deep Phreatic Thermal Explorer (DEPTHX) robot, designed to explore ice-covered Europa, Jupiter’s smallest moon. Partners on the DEPTHX project include Carnegie Mellon University, Southwest Research Institute, Colorado School of Mines, The University of Arizona, and the University of Texas at Austin’s Jackson School of Geosciences. In the words of a NASA press release, The Deep Phreatic Thermal Explorer (DEPTHX) is a 3,300-pound, computerized, underwater vehicle that makes its own decisions. With more than 100 sensors, 36 onboard computers, and 16 thrusters and actuators, it decides where to swim, which samples to collect, and how to get home.

Exploring El Zacatón pit was considered to be an ideal preliminary test of the DEPTHX autonomous robot, which is about the size of a go-kart. The robotic vehicle successfully generated a highly detailed sonar map of the sinkhole, and obtained samples of water and biotic material from the walls, discovering several new phyla of bacteria in the process. Its next challenge is to explore beneath the ice of West Lake Bonney in Antarctica.

At El Zacatón, the sonar study showed that the sinkhole has a total depth of 335 meters: the lake is 319 meters deep at its deepest point, and its surface is 16 meters below the height of the sinkhole’s rim.

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Mexico’s geology and landforms are analyzed in chapters 2 and 3 of Geo-Mexico: the geography and dynamics of modern Mexico.  Buy your copy of this book today!

Mar 312016
 

The River Atoyac, a river more than 120 kilometers (75 miles) long, in the state of Veracruz, has suddenly dried up. The dramatic disappearance of the river is believed to be due to the collapse of the roof of a cavern in the underlying limestone. This caused the formation of a narrow sinkhole, 30 meters (100 feet) long, that now swallows the river and diverts its water underground.

rio_atoyac-mapa-el-universal

Drainage basin of the Río Atoyac. Credit: El Universal

The collapse happened on Sunday 28 February; residents of the small ranch town of San Fermín heard a thunderous noise at the time. Within 48 hours, the river had disappeared.

The River Atoyac rises on the slopes of the Pico de Orizaba, Mexico’s highest peak. Unfortunately, the cavern collapse occurred only 3 kilometers from the river’s source, leaving almost all of its course dry, with potentially serious consequences for up to 10,000 people living in the river basin who have now lost their usual water supply.

The disappearance of the river will also have adverse impacts on fauna and flora, and jeopardize sugar-cane farming and other activities downstream. The fauna of the river included fresh-water crayfish (langostinos) which were an important local food source.

The municipalities affected are Amatlán de los Reyes, Atoyac, Yanga, Cuitláhuac, Felipe Carrillo Puerto, Cotaxtla, Medellìn and Boca del Río.

The course of the river approximately follows that of federal highway 150D, the main toll highway between the cities of Orizaba and Veracruz.

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Mexico’s tallest waterfalls

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Aug 032015
 

As we saw in “How long is Mexico’s coastline?“, geographical “facts” and “records” are often not quite as simple to determine as might appear at first sight.

Take waterfalls for example. Mexico’s “highest” waterfalls are not necessarily the same as Mexico’s “tallest” waterfalls, since height refers to elevation, rather than stature. I’m not sure which is Mexico’s highest waterfall, but assume it is likely to be a small waterfall near the summit of one of Mexico’s many major volcanic peaks.

Mexico’s tallest waterfall, on the other hand, is well-known, or is it? Older sources still list the Cascada de Basaseachic in the Copper Canyon region of northern Mexico as the country’s tallest waterfall. That waterfall is 246 meters (807 feet) tall, according to geographer Robert Schmidt, a calculation subsequent confirmed by measurements made by members of a Mexican climbing expedition.

This short Postandfly video shows the Basaseachic Waterfall from the air:

The Basaseachic Waterfall is normally considered to operate year-round, though very little water flows over it on some occasions during the dry season.

In terms of total drop, however, and if we include waterfalls that are seasonal, the Basaseachic Waterfall is overshadowed by the nearby Cascada de Piedra Bolada (Volada). The Piedra Bolada Waterfall, has a total drop of 453 meters (1486 feet), but flows only during the summer rainy season. It is much less accessible, and its true dimensions were only worked out for the first time by an expedition as recently as 1995 by members of the Speology Group of Ciudad Cuauhtémoc, led by Carlos Lazcano.

This latter sections of this amateur video of the Piedra Bolada Waterfall show some of the amazing scenery in this remote area of Mexico:

Curiously, there is some debate as to whether this waterfall should be called Cascada de Piedra Volada (which would translate as the “Flying Stone Waterfall”) or Cascada de Piedra Bolada (“Round Stone Waterfall”). According to members of the Speology Group of Ciudad Cuauhtémoc, its true name is definitely Piedra Bolada, a name referring to a spherical stone, and used in addition for the local stream and for the nearest human settlement.

So, which is Mexico’s tallest waterfall? Well, it all depends…

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30 top geotourism sites in Mexico (Geo-Mexico special)

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May 142015
 

Mexico has literally thousands of geotourism sites (locations where the primary recreational attraction is some phenomenon of geographic importance, such as a coral reef, mangrove swamp, volcano, mountain peak, cave or canyon. Many of Mexico’s geotourism sites are geomorphosites, where the primary attraction is one or more ”landforms that have acquired a scientific, cultural/historical, aesthetic and/or social/economic value due to human perception or exploitation.” (Panniza, 2001)

Here is a partial index (by state) to the geotourism sites described on Geo-mexico.com to date:

Baja California Sur

Chiapas

Chihuahua

Colima

Hidalgo

Jalisco

México (State of)

Michoacán

Morelos

Nayarit

Nuevo León

Oaxaca

Puebla

Querétaro

Quintana Roo

San Luis Potosí

Sonora

Tamaulipas

Veracruz

Reference:

  • Panizza M. (2001) Geomorphosites : concepts, methods and example of geomorphological survey. Chinese Science Bulletin, 46: 4-6

How similar are Mexico’s two major deserts, the Sonoran Desert and the Chihuahuan Desert?

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May 292014
 

There are four desert areas in North America. Two of these areas (Great Basin and Mojave) are in the USA. The other two (the Sonoran Desert and the Chihuahuan Desert) are almost entirely in Mexico, but extend northwards across the border. The Sonoran Desert includes most of the Baja California Peninsula, together with the western part of the state of Sonora. The Chihuahuan desert is the northern section of the Central Plateau, including the northern parts of the states of Chihuahua.

The Chihuahuan Desert has been intensively studied by scientists interested in the possibility of life on Mars – see this New York Times article: Learning About Life on Mars, via a Detour to Mexico.

In a previous post – Why is northern Mexico a desert region? , we saw how the combination of the descending air of the Hadley Cell, which results in surface high pressure, and the effects of rain shadows resulting from neighboring mountain ranges contribute to the low annual rainfall total characteristic of both Mexico’s desert areas.

deserts-colorWhile these two deserts both experience an arid climate, they also have many differences.

Area

The Sonoran Desert has an area of about 311,000 square kilometers (120,000 sq mi). The Chihuahuan Desert has an area of about 362,000 square kilometers (139,769 sq mi).

Elevation

The Sonoran Desert is lower in elevation that the Chihuahuan Desert, with some parts (in the USA) lying below sea level. The Chihuahuan Desert varies in elevation from 600–1675 m (1969–5495 ft).

Summer temperatures

The Sonoran Desert tends to have higher summer temperatures than the Chihuahuan Desert, though even in the Chihuahuan Desert, daytime temperatures in summer are usually between 35 and 40̊C (95-104̊F).

Seasonal rainfall patterns

The ratio of winter to summer rainfall decreases from west to east. Most of the Sonoran Desert (to the west) has a bimodal rainfall regime with spring and summer peaks. On the other hand, most of the limited rain that falls in the Chihuahuan Desert comes in late summer.

The Chihuahuan Desert has a mean annual precipitation of 235 mm (9.3 in), though annual totals vary from 150 to 400 mm (6–16 in).

Vegetation, fauna and biodiversity

These seasonal rainfall differences result in significant differences in the vegetation of the two areas.

The bimodal precipitation in the Sonoran Desert provides two flowering seasons each year. Some plants bloom in spring, following winter rains, while others flower in late summer, following summer rains. Typical plants in the Sonoran Desert include columnar cacti (Cereus spp.) such as sahuaro, organ pipe, and cardon, as well as many other types of cacti, including barrels (Echinocereus), chollas (Opuntia spp.) and prickly pear (Opuntia spp.). Other succulent plants are also common.

More than 60 mammal species, 350 bird species, 20 amphibian species, 100 reptile species, 30 native fish species, 1000 native bee species, and 2000 native plant species have been recorded in the Sonoran Desert. The Sonoran Desert includes the Colorado River Delta, which was once an ecological hotspot within the desert, fueled by the fresh water brought by the river, though this flow has become negligible in recent years. See, for example, Will the mighty Colorado River ever reach its delta?

The vegetation of the Chihuahuan Desert is dominated by grasslands and shrubs, both evergreen and deciduous. Common species include tarbush (Flourensia ternua), whitethorn acacia (Acacia constrictor) and creosote bush (Larrea tridentata). The Chihuahuan desert has small cacti; succulent agaves (Agave spp.) and yuccas. Plants bloom in late summer, following the summer rains.

The Chihuahuan Desert is home to about 350 of the world’s 1500 known species of cactus, and includes the fascinating area of Cuatro Ciénegas, which has an unusually high number of endemic plant species and is one of the world’s richest hotspots for locally endemic cacti.

The Chihuahuan Desert is considered to be one of the three most biologically rich and diverse desert ecoregions in the world, rivaled only by the Great Sandy Tanmi Desert of Australia and the Namib-Karoo of southern Africa. However, settlements and grazing have heavily degraded the natural vegetation of some parts of the Chihuahuan Desert.

he Chihuahuan Desert has about 3500 plant species, including up to 1000 species (29%) that are endemic. The high rate of endemism (true for cacti, butterflies, spiders, scorpions, ants, lizards and snakes) is due to a combination of the isolating effects of the basin and range topography, climate changes over the past 10,000 years, and the colonization of seemingly inhospitable habitats by adaptive species. See here for more details of the flora and fauna of the Chihuahua Desert.

Landforms

This basin and range landscape of the Sonoran Desert trends north-northwest to south-south-east. Parallel faulted blocks are separated by alluvial bajadas (broad, debris-covered slopes), pediments and plains, which become wider approaching the coast. Despite being a desert area, this region exhibits many features that have resulted from water action, including wadis, salt flats, stream terraces and alluvial fans.

For a fuller description of the landforms of the Sonoran Desert, see this extract from A Natural History of the Sonoran Desert (edited by Steven J. Phillips and Patricia Wentworth Comus) published by the Arizona-Sonora Desert Museum.

The Sonoran Desert includes the subregion of the Sierra of Pinacate (part of El Pinacate and Gran Desierto de Altar Biosphere Reserve) with its distinctive volcanic cones, craters and lava flows. For more details, see The landforms of the El Pinacate and Gran Desierto de Altar Biosphere Reserve.

The landforms of the Chihuahuan Desert have been molded by tectonic uplift and erosion. Steep-sided but low hills are separated by wide bajadas from former lake beds and alluvial plains, occupying inland basins known as bolsons. Many parts form closed, interior basins with no external drainage. South of Ciudad Juárez, at Samalayuca, is one of Mexico’s most extensive areas of sand dunes. This is one of the most arid parts of the country, with high levels of salinization.

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World’s longest underground river flows deep beneath the Yucatán Peninsula

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Feb 102014
 

In January 2007, the world’s longest underground river was reported from Mexico’s Yucatán Peninsula. [Prior to that date, the honor was held by the Puerto Princesa Subterranean River in the Philippines]

The Sac Actun (“White Cave”) river system in the Yucatán Peninsula wanders for 153 km (95 miles) through a maze of underground limestone caves. It took British diver Stephen Bogaerts and his German colleague Robbie Schmittner four years to explore the caverns using underwater scooters and specially rigged gas cylinders, before they finally discovered a connection between the Yucatán region’s then second- and third-longest cave systems, known respectively as Sac Actun and Nohoch Nah Chich (“Giant Birdcage”). Following the discovery of a link, the entire system is now known as Sac Actun. The system has a total surveyed length (including dry caves) of 319 kilometers (198 mi), making it the longest cave system in Mexico, and the second longest worldwide. [The longest is the dry Mammoth Cave System, Kentucky, USA, which measures 643.7 km (400 mi) in length].

Sac-Actun cave system

Sac-Actun cave system

Vying with Sac Actun for the title of longest surveyed underwater cave system is the nearby Sistema Ox Bel Ha (“Three Paths of Water”), also in the Tulum municipality of Quintana Roo. As of August 2013, surveys had measured 256.7 kilometers (159.5 mi) of underwater passages.

The underground passages and caverns of the Yucatán Peninsula have been a favored site for cave explorers for decades. Formal mapping of the systems has taken more than 20 years of painstaking work. Access to the systems is via the hundreds of sinkholes (cenotes) that litter the surface of the Peninsula. The Sac Actun system alone includes more than 150 cenotes.

Water management was critical to the Maya as they developed their advanced civilization in this area, a region with very limited surface freshwater. Many of the cenotes in the Yucatán Peninsula have archaeological importance and were utilized by the Maya for ceremonies. Perhaps the best-known (and most visited) cenote is the Sacred Cenote (cenote sagrado) at the archaeological site of Chichen Itza.

The caverns of the Yucatán Peninsula were formed as a result of the slow solution of limestone over thousands of years by percolating, slightly acidic, rainwater. In some cases, cave formations, such as stalactites and stalagmites, have later grown in the caves, formed drip-by-drip from the slow deposition of calcium carbonate from calcium-saturated ground water.

Because the average elevation of the Yucatán Peninsula is only a few meters above sea level, the water in many of the caves is “layered”, with a lens of freshwater overlying a layer of salt water. Rainwater that soaks into the ground becomes ground water, which then moves slowly along the watertable to eventually reach the ocean.

Cave researchers are worried that tourist developments in the Yucatán Peninsula will have adverse impacts on underground water systems, both in terms of water quantity (because of the amounts of fresh water extracted for domestic and tourist use) and in terms of water quality, because even point sources of water pollution (such as excess fertilizers from a golf course) could contaminate underground water supplies over a wide area.

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The landforms of the El Pinacate and Gran Desierto de Altar Biosphere Reserve

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Nov 092013
 

The breathtaking scenery of the El Pinacate and Gran Desierto de Altar Biosphere Reserve in the northern state of Sonora affords visitors a dramatic combination of two very distinct landscape types: volcanic landscapes (El Pinacate) in the east, and sand dunes (Gran Desierto de Altar) towards the west and south.

pinacate-map-googleVolcanic scenery (El Pinacate)

The eastern section of the Biosphere Reserve, El Pinacate, is a dormant volcanic area of around 200,000 ha (2000 sq. km), centered on the El Pinacate Shield (or Sierra Pinacate) which has 3 main peaks: Pinacate, Carnegie and Medio. The El Pinacate Shield is a composite structure, comprised of extensive, successive black and red lava flows, some more than 20 km long, seperated by desert pavement. The El Pinacate Shield boasts a wide array of volcanic phenomena and geological formations. Most of the lava is basaltic (alkaline) in composition, making it relatively fluid when molten; it is mainly of the aa (blocky) type, though some pahoehoe (ropy) lava is also found. The total volume of lava is estimated at between 150 and 180 km3.

Elegante Crater, El Pinacate

Elegante Crater, El Pinacate (example of a maar)

Besides the lave flows, the Pinacate area has more than 400 cinder cones (formed 1.2 million years ago) and several lava tubes. The lava flows and cinder cones are only a prelude to the most visually striking features in the reserve: 10 enormous, deep, and almost perfectly circular maars (steam explosion craters). Maars are believed to originate from a combination of explosion caused by groundwater coming into contact with hot lava or magma and subsequent collapse. The maars of El Pinacate are rivalled only by similar formations in Africa. The largest single maar is El Elegante, formed 32,000 years ago, which is 1,400 meters (4,600 feet) from rim to rim and 140 meters (460 feet) deep. It takes visitors a two to three-hour hike to reach its rim and be rewarded by a spectacular view.

The volcanic forms of El Pinacate are relatively recent in geological terms, most having been formed during the Quaternary Period, which began some 2.8 million years ago. The most recent volcanic activity in this area was only about 11,000 years ago. Some volcanologists believe that some of these craters could become active again in the future, with the potential to form volcanoes up to a few hundred meters in height.

Ron Mader, the founder of Planeta.com and a foremost authority on responsible tourism in Mexico, has marveled at the “bizarre and mind-boggling scenery” of El Pinacate., which so resemble the lunar landscape that between 1865 and 1970 it was used by NASA as a training ground for astronauts preparing for the moon landings. The lava field is so vast and sharply defined that it later turned out that the astronauts could easily recognize it from space!

Sand dunes (Gran Desierto de Altar)

The western and southern parts of the El Pinacate and Gran Desierto de Altar Biosphere Reserve have entirely different scenery. The Gran Desierto de Altar is North America’s largest field of active sand dunes (erg). Several types of dunes are represented here, the tallest reaching 200 meters in height.

The sand needed to form and maintain these dunes comes from the fluvial and deltaic sediments of the Colorado River delta (to the west), the beaches of the Sea of Cortés/Gulf of California (to the south), the River Sonoyta (to the east) and the smaller river and stream fans formed in those parts of the reserve where there are volcanic and granitic mountains.

Sand dunes of Gran Desierto de Altar

Sand dunes of Gran Desierto de Altar

Prior to the opening of the Sea of Cortés (Gulf of California), vast amounts of sediment accumulated in this region brought by rivers of which little trace remains today. The creation of the Sea of Cortés, 5.3 million years ago, shortened the rivers and increased their average gradient (rejuvenation), causing them to cut into the pre-existing landscape leaving behind river terraces, remnants of the former higher level floodplains.

The fields of sand dunes of the Gran Desierto de Altar cover more than 550,000 hectares (5700 sq.km.) Several different kinds of sand dunes are found here–linear, crescent-shaped (barchans) and star-shaped–and they can be simple, compound or complex, depending on seasonal changes in the direction and strength of the wind.

Although linear dunes dominate (70%), crescent-shaped complex dunes and star-shaped dunes are of more interest because they exist in only a few locations in the world. Spectacular and very large star-shaped dunes, up to 200 meters high, occur both singly and in long ridges up to 48km in length. Star-shaped dunes possibly evolved from crescent dunes which changed their direction of movement becoming “reversing dunes”. Side winds may account for the multiple arms of some star-shaped dunes.

Other features – Granite massifs

In addition, there are several granite massifs (inselbergs), such as the Sierra del Rosario, emerging like islands from the sandy desert flats and dunes. They range in elevation from 300 to 650 meters above sea level. They represent another remarkable landscape feature harboring distinct plant and wildlife communities.

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Oct 242013
 

Mexico’s latest UNESCO World Heritage Site is the El Pinacate and Gran Desierto de Altar Biosphere Reserve in Sonora, added to the UNESCO list in June 2013. Mexico now has 32 World Heritage Sites.

The El Pinacate and Gran Desierto de Altar Biosphere Reserve is part of the Sonoran desert, which extends from Sonora into the northern part of Baja California, and across the U.S. border into Arizona and California. The reserve covers 714,566 hectares with an additional 354,871 hectares of buffer zone. It is a relatively undisturbed portion of the Sonoran desert, and offers visitors a dramatic combination of two very distinct landscape types: volcanic landscapes (El Pinacate) and sand dunes (Gran Desierto de Altar).

pinacate-map-googleThe biosphere reserve is immediately south of the U.S. border, west of the Lukeville (Arizona) – Sonoyta (Sonora) border crossing, and 50 km (30 miles) north of the fishing and tourist town of Puerto Peñasco. The San Luis Río Colorado–Sonoyta section of Mexican federal highway 2 (which runs from Mexicali to Caborca) skirts the northern section of the reserve. Puerto Peñasco is connected to Sonoyta by highway 8. There are entrances to the park from highway 2, 50 km west of Sonoyta, and from highway 8, mid-way between Sonoyta and Puerto Peñasco.

Despite being a desert area, most parts of the biosphere reserve do receive occasional rainfall, which gives this area more biodiversity than is true for most deserts.

El Pinacate and Gran Desierto de Altar Biosphere ReserveVaried scenery

The eastern section of the biosphere reserve, El Pinacate, is a dormant volcanic area of around 200,000 ha (2000 sq. km), centered on the El Pinacate Shield (or Sierra Pinacate) which has lava flows, cinder cones, lava tubes and circular maars (steam explosion craters). Ron Mader, the founder of Planeta.com and a foremost authority on responsible tourism in Mexico, has marveled at the “bizarre and mind-boggling scenery” of El Pinacate. The geology and landforms of this area so resemble the lunar landscape that between 1865 and 1970 NASA used it as a training ground for astronauts preparing for the moon landings. The lava field is so vast and sharply defined that it later turned out that the astronauts could easily recognize it from space!

The western and southern parts of the El Pinacate and Gran Desierto de Altar Biosphere Reserve are entirely different. The Gran Desierto de Altar is North America’s largest field of active sand dunes (erg), more than 550,000 hectares (5700 sq.km.) in area. Several types of dunes are represented here, the tallest reaching 200 meters in height, including linear, crescent-shaped (barchans) and star-shaped dunes.

Flora and Fauna

The highly diverse mosaic of habitats in the biosphere reserve is home to complex communities and a surprisingly high species diversity. More than 540 species of vascular plants, 44 mammals, more than 200 birds and over 40 reptiles inhabit this seemingly inhospitable desert. All feature sophisticated physiological and behavioural adaptations to the extreme environmental conditions. Insect diversity is high, though not fully documented. Several endemic species of plants and animals exist, including two freshwater fish species.

The flora in Sierra Pinacate includes the sculptural elephant tree (Bursera microphylla). The name “Pinacate” derives from pinacatl, the Nahuatl word for the endemic desert stink beetle. The biosphere reserve has large caves inhabited by the migratory lesser long-nosed bat (Leptonycteris curasoae yerbabuenae), which is an important pollinator and seed dispersal vector, and the endangered fish-eating bat (Myotis vivesi); both species are endemic.

Other noteworthy species in the reserve include the threatened Sonoran pronghorn (Antilocapra americana sonorensis), an endemic subspecies of restricted habitat and the fastest land mammal in North America; bighorn sheep (Ovis canadensis mexicana), the mule deer (Odocoileus hemionus) and gray fox (Urocyon cinereoargenteus), the Gila monster (Heloderma suspectum) and desert tortoise (Gopherus agassizii).

Human occupation and use

El Pinacate and Gran Desierto de Altar contains numerous archaeological remains, some dating back more than 20,000 years. It is an important cultural site for the indigenous Tohono O’odham people who consider El Pinacate peak, where they still perform sacred ceremonies, as the place where  creation occurred.

Management issues

The El Pinacate section of the biosphere reserve was first designated a “protected area” in 1979. In 1993, it was a declared a Biosphere Reserve, along with the Gran Desierto de Altar, by then president Carlos Salinas de Gortari. The biosphere reserve is managed by Mexico’s National Commission of Natural Protected Areas (Conanp), in collaboration with the Sonora state government and the Tohono O’odham people.

The number of people visiting the reserve has risen rapidly from fewer than 6,000 in 2000 to more than 17,500 in 2010. The two major challenges that management needs to take into account are how to ensure that indigenous views about the reserve’s use are respected, and how to limit negative impacts on the reserve from nearby tourism developments.

The potential negative impacts include:

  • increased vehicle traffic, resulting in ecological disturbance, littering and wildlife road kills.
  • pressure to extend the limited existing road infrastructure by adding new roads, though this might lead to more exotic (alien) invasive species.
  • increased habitat damage from the growing use of off-road vehicles

UNESCO considers that, “The most critical long term management issue is to address potential problems derived from tourism-related water consumption.”

Given that this reserve is on the Mexico-U.S. border, transboundary cooperation is essential, and UNESCO actually recommends that the best way forward is to establish a Transboundary Protected Area, extending into Arizona.

The combination of a volcanic shield with spectacular craters and lava flows, almost entirely surrounded by an immense sea of dunes, makes this an area of great scientific interest, and an ideal laboratory for researchers interested in geology and geomorphology.

[Note: This post makes extensive use of UNESCO’s description of the biosphere reserve, with additional information from a variety of other sources.]

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Geotourism in Mexico: García Caves (Grutas de García) in Nuevo León

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Oct 032013
 

The Garcia Caves (Grutas de García) are located in the Cumbres de Monterrey National Park, 9 km from the small town of Villa de García, and about 30 km from the city of Monterrey (state capital of Nuevo León). The highest point in the park is Copete de las Águilas which rises to 2260 m (7,410 ft) above sea level, but its best known peak is Saddle Hill (Cerro de la Silla), the distinctive saddle-shaped hill that overlooks the city.

Much of the park, including the mountains, are composed of sedimentary rocks that were originally laid down as marine sediments and then subsequently folded, uplifted and exposed to erosion. The extensive areas of limestone in the park, which date from the Cretaceous period, have been subject to karstification over 50 to 60 million years, which has resulted in typical karst landforms such as sinkholes, caves, cave formations and underground streams.

The Garcia Caves, one of the largest cave systems in Mexico, are deep inside the imposing Cerro del Fraile, a mountain whose summit rises to an elevation of 1080 meters above sea level, more than 700 meters above the main access road. The entrance to the caves is usually accessed via a short ride on a 625-meter cable car that was built to replace a funicular railway.

The cave system was first reported in 1843 by the Marmolejo family who informed their local prist Juan Antonio Sobrevilla that they had stumbled across it while looking for firewood.

Grutas de García. Credit: María de Lourdes Alonso

Grutas de García. Credit: María de Lourdes Alonso

Guided tours of the cave system show visitors some of its 27 separate chambers along a 2.5-kilometer (1.6 mile) route. The full system extends more than a kilometer further into the mountain reaching depths of more than 100 meters (340 feet) beneath the surface. The limestone of the cave walls contains lots of marine fossils. The caves have extensive and impressive formations of dripstone, including stalactities, stalagmites and other forms.

Unlike the suffocating heat of the Naica Crystal Caves in Chihuahua, the cave temperature here remains about 18̊C (65̊F) all year.

The chambers and formations have been given whimsical and imaginative names such as

  • “El salón de la luz” (The Light Chamber) where the natural translucence of the ceiling rock allows light from the outside to filter through.
  • “La octava maravilla” (The Eighth Wonder), a natural column formed where a stalagmite growing from the floor joined a stalactite, growing from the ceiling
  • “El mirador de la mano”, a stalagmite shaped like a human hand.
  • “El Nacimiento” (The Nativity),
  • “La Fuente Congelada” (The Frozen Fountain),
  • “La Torre China” (The Chinese Tower),
  • “El teatro” (The Theatre), and
  • “El Árbol de Navidad” (The Christmas Tree).

Want to read more about caves in Mexico?

Visit John Pint’s website for a selection of his writing, with many original articles, illustrated with great photographs, about many individual caves in Mexico.

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