Oct 062016
 

El Pico de Orizaba, or Citlaltépetl (= “star”), is Mexico’s highest peak, rising to a summit 5,610 meters (18,406 feet) above sea level. The third highest peak in North America, it is also that region’s highest volcano, responsible for major eruptions in 1569, 1613 and 1687. The mountain was first explored by scientists as long ago as 1838.

Located east of Mexico City, some 30 kilometers (20 miles) northwest of the city of Orizaba, it is regularly climbed today by well-equipped groups, especially during the dry season, from December to April. Its classical cone shape masks an impressively large crater, which is more than 300 meters (1,000 feet) deep. The volcano and surrounding area were declared a national park by President Lázaro Cárdenas in 1936; the decree took effect the following January.

Among the first recorded ascents is that in August 1838 by a group of several European botanists: Henri Galeotti, Nicolas Funck, Auguste Ghiesbreght and Jean-Jules Linden.  The group spent eleven days on the volcano and their subsequent accounts of the expedition show that they definitely reached the summit. Afterwards, they went on to have distinguished careers in their specialist fields.

By the time of the climb, Henri Guillaume Galeotti (1814-1858) had already written a landmark article about Lake Chapala, and made numerous botanical discoveries in Mexico. He went on to become Director of the Royal Botanical Gardens in Brussels, Belgium.

Less is known about the achievements of Nicolas Funck (1816-1896), who continued traveling in Mexico until 1842. He subsequently became director of Brussels Zoo (1861) and then Cologne Zoo.

After the climb, Auguste Ghiesbreght (1810-1893) set up his own business in Mexico, making a living by supplying plants and natural history specimens to European collectors and his botanist business partners. Who knows? Perhaps the plans for a cacti-exporting business (Galeotti) and large-scale orchid cultivation (Linden) were hatched while the group of young friends were battling their way towards the peak of Orizaba.

Jean Jules Linden (1817-1898), born in Luxembourg, collected for the Belgian government in Brazil, Mexico and Guatemala, before becoming one of the world’s most celebrated importers of plants. He set up nurseries for exotic plants in Brussels and Ghent in Belgium, as well as on the French Mediterranean coast. He also directed Brussels Zoo. He is credited with introducing and popularizing numerous plants, including begonias, palm trees and orchids. His superb publications on orchids and his marketing skills won him world-wide respect.

The nineteenth century craze for orchids in Belgium had numerous parallels with the craze three hundred years earlier for tulips in the Netherlands. The nouveau-riche industrialists satisfied their passion for expensive and unusual orchids by buying them from Linden who was propagating and growing them in massive, industrial-scale glasshouses. Even the Russian czar bought orchids from Linden!

El Pico de Orizaba (from Oswald’s Summerland Sketches, 1880)

The explorations of Galeotti and his friends resulted in the volcano becoming much better known. A decade later, Carl Sartorius, an artist of German extraction who collected plants for the Berlin Botanical Gardens, and who owned the El Mirador hacienda close to the volcano, organized an expedition to reach the summit. When they reached the top, they found a simple plaque there already, left by two US soldiers, F. Maynard and G. Reynolds, who had served as troopers in Winfield Scott’s army during the 1846-1848 Mexican-American war.

Not surprisingly, the upper reaches of El Pico de Orizaba (above about 4,000 meters) are snow-capped all year. Though someone had probably skied down the mountain previously, the first recorded descent on skis was made by W. Furlinger in 1974. Schemes to open a skiing resort on its slopes have been suggested several times. Before any budding entrepreneurs get carried away with the possibilities, it should be pointed out that setting up permanent ski runs on the slopes of El Citlaltépetl may not be too smart an idea, given the likely impact of global warming.

This is an edited and updated version of an article originally published on MexConnect.

Acknowledgment

My thanks to Dr. Winston Crausaz. the author of Pico de Orizaba or Citlaltepetl (Geopress International, 1993), whose valuable comment on the original post (see below) has now been incorporated into the updated version above.

Mexico’s volcanoes, mountains and relief features are examined  in chapters 2 and 3 of Geo-Mexico: the geography and dynamics of modern Mexico.

Recent eruptions of Colima Volcano, el Volcán de Colima

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Jul 122015
 

Colima Volcano (aka el Volcán de Colima or el Volcán de Fuego) continues to erupt, displaying its fiery temper by throwing massive plumes of ash and smoke several kilometers into the air. One recent eruption caused a plume of ash seven kilometers high.

 

Following the eruptions of 10 and 11 July 2015 (see video clip from Webcams de México), a state of emergency has been declared by the state of Colima in 5 municipalities: Colima, Comala, Coquimatlán, Cuauhtémoc and Villa de Álvarez. This enables rapid access to state and federal funds in preparing to cope with any potential disaster.

A precautionary evacuation has been ordered of all communities within a 12-kilometer radius of the volcano’s crater. The 50-60 residents of the closest community to the volcano, La Yerbabuena, live barely eight kilometers (five miles) away from the crater. Five centimeters (two inches) of ash fell on La Yerbabuena in the past few days.

Authorities are concerned that heavy summer rains could generate dangerous and very fast-moving lahars. Lahars are mudflows of volcanic ash, pumice and rocks; they can travel at velocities of up to 100 km/h and move huge boulders and objects as large as houses.

Where is Colima Volcano (Volcán de Colima)?

Location of Colima Volcano

Location of Colima Volcano (Volcán de Colima). Credit: Tony Burton / Geo-Mexico

The volcano is one of the westernmost volcanoes in Mexico’s Volcanic Axis, which straddles the country from west to east. Colima Volcano’s summit is only 8 km (5 miles) from the inactive Nevado of Colima volcano, Mexico’s sixth-highest peak, which rises 4260 m (13,976 ft) above sea level. (Lovers of geographical trivia should note that, despite their names, the summits of both volcanoes are actually located in the state of Jalisco, not in the state of Colima.)

Colima Volcano is considered one of Mexico’s most dangerous volcanoes. Numerous villages in its shadow keep a wary eye on its level of activity, and emergency evacuations have become a regular event over the past fifty years.

How high is Colima Volcano?

The elevation of Colima Volcano is officially given as 3820 m (12,533 ft) above sea level. In the past 400 years, it has been the most active volcano in Mexico, having erupted at least 30 times since 1576. Recent activity means that this exact height may no longer be correct.

The eruption of Colima Volcano on 21 January 2015, shown in this short video, is typical of recent activity.

How often does it erupt?

Historically, the eruptions of the volcano have fallen into a definite cyclical pattern with periods of activity, each lasting about 50 years, interspersed with periods of dormancy. The first cycle of activity (after the Spanish arrived in Mexico) was between 1576 and 1611. Major eruptions occurred in 1680 and 1690, and further complete cycles occurred between 1749 and 1818, and from 1869 to 1913.

The current eruption cycle

Most geologists agree that current activity is part of the fifth cycle, which began in 1961. Judging by past performance, we should be nearing the end of this cycle, though volcanoes can be extremely unpredictable, so don’t bet your house on this happening within the next decade.

Activity has intensified in the past couple of years. In early 2013, we reported that Colima Volcano had erupted, destroying a lava dome first created in 2007 and later that year we looked at how Popocatapetl Volcano and Colima Volcano continued to erupt. At that time, experts monitoring the volcano were reporting up to 200 eruptive events a day, with numerous minor emissions of lava. Colima Volcano has been exhibiting four distinct types of volcanic activity in recent years:

  • lava dome growth
  • explosive eruptions
  • flank collapse
  • lava flows.

In early 2015, activity began to intensify, with several spectacular eruptions, sending ash and dust up to 8 or 9 kilometers (5-6 miles) into the air. Ash fell on towns up to 25 kilometers (15 miles) away from the volcano, in locations including Tuxpan, Zapotiltic and Ciudad Guzmán, but with no loss of life, or significant property damage.

The volcano can be viewed via this permanent fixed webcam operated by Webcams de Mexico. Below the main image on that site are links to 1-minute time-condensed videos showing the past 24 hours of activity.

Three maps (PDF format, Spanish-language keys and text) showing the areas likely to be affected by the volcanic hazards associated with Colima Volcanocan be found via this webpage of Mexico’s National Center for Disaster Prevention (Centro Nacional de Prevención de Desastres, CENAPRED). :

The area around the Colima Volcano is described in more detail in chapter 15 of my Western Mexico, a Traveler’s Treasury (4th edition; Sombrero Books, 2013).

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Mexico’s webcams

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Jun 292015
 

There are thousands of webcams operating in Mexico offering armchair geographers the opportunity to see up-to-date images of active volcanoes, megacities, archaeological sties, small towns and tourist resorts.

Many of the major webcams are listed at Webcams de México, which has several great features once you’ve chosen a particular webcam, including access to prior images for any date and time, or the ability to compile an instant time-lapse video covering any period of time.

Links to webcams listed at Webcams de México:

Explore Mexico via its webcams! Enjoy!

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The art of Mexican volcanoes

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Apr 162015
 

An art exhibition entitled “Mexican Volcanoes” is opening in Mexico City next week. The show opens on Tuesday 21 April, at noon, at the offices of the Mexican Society for Geography and Statistics (Sociedad Mexicana de Geografía y Estadística) at Justo Sierra #19, in the Historic Center of the city. The Society is one of the world’s oldest geographic societies, having been founded 18 April 1833. (The Royal Geographical Society in the U.K. was founded in 1830; the National Geographic Society in the USA was founded in 1888).

Invitacion frente

This exhibition, which will close on 29 April, is being arranged by Lewinson Art, a Mexican art firm that specializes in promoting artists via a virtual gallery and exhibitions. Artists were invited to submit works (paintings, drawings, engravings, photographs) relating to the subject “Mexican Volcanoes”.

Detail of lithograph by Casimiro Castro of Railway near Orizaba, Veracruz

Detail of lithograph by Casimiro Castro of Railway near Orizaba, Veracruz, with Pico de Orizaba in the background

Historically, Mexico’s volcanoes have been especially fertile ground for Mexican artists, from the great landscapes of José María Velasco to Casimiro Castro and the colorful and energetic “aerial landscapes” of Dr. Atl (Gerardo Murillo).

dr-atl-paricutin

Dr. Atl (Gerardo Murillo): Paricutin Volcano

Artists represented in this interesting exhibition include:

Agustín Aldama, Mercedes Arellano, José Luis Briseño, Rosi Calderón, Argelia Castañeda, Becky Esquenazi, Gabriela Estrada, Tere Galván, Gabriela Horta, Ana Gabriela Iñiguez, Débora Lewinson, Manuel Martinez Moreno, Nadine Markova, Ausberto Morales, Francoise Noé, Merle Reivich, Fernando Reyes Varela, Homero Santamaría, Arcelia Urbieta, Ariel Valencia , Primo Vega and Lucille Wong.

The volcanoes depicted in the show include Popocatepetl, Iztaccihuatl, Cofre de Perote and the Nevado de Toluca (Xinantecatl).

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Popocatepetl Volcano continues its very active phase

 Mexico's geography in the Press, Other, Updates to Geo-Mexico  Comments Off on Popocatepetl Volcano continues its very active phase
Aug 092014
 

Popocatepetl Volcano, near Mexico City continues to be very active, with smoke and ashes belching up to 1000 meters above the crater rim. Mexico’s National Disaster Prevention Agency Cenapred, reports that the volcano had 82 “low intensity” exhalations on 7 August 2014, four of which contained “explosive material”.

Popocatapetl, 8 August 2014. Credit: Cenapred.

Popocatapetl, 8 August 2014. Credit: Cenapred.

The agency also reported that many mionr tremors hd been recorded, including one harmonic tremor lasting 56 minutes. Geologists believe that the volcano is currently destroying dome number 50 even as dome number 51 begins to form. Dome #51 is currently about 70 meters in diameter. Renewed explosions, together with some ash fall is predicted for the coming days.

The Volcanic Traffic Light remains at Yellow Phase 2.

For a series of images dated 8 August 2014, see Images of 8 of ago of 2014

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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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Popocatepetl Volcano puts on an explosive show

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Jul 102013
 

This 30-second video update on the eruption of Popocatepetl Volcano speaks for itself. Webcams have made the life of armchair geologists (even those of us who quite like exploring volcanic craters, provided the volcano in question is extinct or at least dormant) a whole lot easier!

The alert level remains at Yellow Phase 3, the highest stage before the two “Alarm” stages of Red 1 and Red 2.

Travel tips:

Several international flights into and out of Mexico City over the past week have been either diverted to other airports or cancelled. If you are flying into Mexico City in the next few days, check with your airline.

Ash has fallen (in varying amounts) over many parts of the city during this time. To avoid getting any ash into your lungs (not good!), consider wearing a damp face mask wherever/whenever the air is not clear.

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The volcanic calderas of Mexico’s Volcanic Axis

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Jul 082013
 

There is still lots of work needed to fully unravel the geological secrets of Mexico’s Volcanic Axis which crosses the country between latitudes 19̊ and 21̊ North. Unlike most volcanic belts elsewhere in the world, this one does not appear at first sight to correspond to any plate boundary. Another of the mysteries of this volcanic region, where igneous upheavals have shaped the landscape for several million years, is the relative dearth of calderas, the “super craters” formed either by collapse or by giant explosions.

While the toponym La Caldera is used fairly commonly in Mexico’s volcanic regions for a volcano or volcanic crater, geologists restrict the term to the much larger landform that results from the collapse or super-explosion of a volcano. Even so, there is still some debate among specialists as to the precise definition of the term caldera.

Geologists have proposed a threefold division of the Volcanic Axis, based on differences in the volcanic landforms, in terms of their type, structure, age, morphology and chemistry.

volcanic-axis

The western sector (see map below) extends from the western coast of Mexico to Lake Chapala (including the lake basin). The central sector covers the area between Lake Chapala and the twin volcanoes of Popocatepetl and Ixtaccihuatl, close to Mexico City. The eastern sector includes these twin volcanoes and extends as far as Mexico’s Gulf Coast.

Mexico's Volcanic Axis (Fig 2.2 of Geo-Mexico, the geography and dynamics of modern Mexico. All rights reserved.

Mexico’s Volcanic Axis (Fig 2.2 of Geo-Mexico, the geography and dynamics of modern Mexico). All rights reserved.

The only caldera recognized in the western section is that of La Primavera, the forested area west of Guadalajara, whose formation we considered in

In the central and eastern sections of the Volcanic Axis, several other calderas have been recognized. They include (from west to east):

  • Los Azufres
  • Amealco
  • Mazahua
  • Huichapan
  • Los Humeros
  • Las Cumbres

Los Azufres

The precise origin of the Los Azufres caldera, in Michoacán, is still debated. The caldera is the site of an important geothermal power station with an installed capacity of 188 MW. (Mexico is the world’s fourth largest producer of geothermal energy, after USA, the Philippines and Indonesia.) The geothermal heat in this area is also used to heat the cabins in a local campground, and to dry wood and process fruit.

Amealco

The Amealco caldera is in the central part of the Mexican Volcanic Axis, midway between the towns of San Juan del Río and Maravatio. It dates from Pliocene times and has been heavily eroded since. It is about 11 km wide and 400 m deep and was the origin of great sheets of pyroclastic flow deposits (ignimbrites) with a total volume of around 500 cubic km.

Mazahua

Mazahua is a collapse caldera, 8 km in width, near the village of San Felipe del Progreso in the western part of the State of Mexico.

Huichapan

The Donguinyó-Huichapan caldera complex is 10 km in diameter and in the central sector of the Volcanic Axis. It appears to be two overlapping calderas, dating from around 5 million and 4.2 million years ago respectively. The rocks from the older caldera are intermediate to basic in composition, while those from the more recent caldera are acidic (high silica) rhyolites.

Los Humeros

The Los Humeros caldera is in the state of Puebla, close to its border with Veracruz. It is 55 km west-north-west of the city of Xalapa (Veracruz), relatively close to Teziutlán (Puebla). The main caldera (summit elevation 3150 m) is about 400 m deep and roughly oval in shape, with a diameter which varies from 15 to 21 km. It was formed about 460,000 years ago by the collapse of the underground magma chamber. Prior to collapse, lava emitted from this vent had covered 3500 square km with ignimbrite. Later, two smaller calderas formed nearby, with ages of about 100,000 years (Los Potreros caldera) and 30,000 years (El Xalapazco) respectively. Volcanic activity in this area has been utilized to produce generate geothermal power (installed capacity: 40 megawatts).

Las Cumbres

The easternmost caldera in Mexico is Las Cumbres, 15 km north of Pico de Orizaba, Mexico’s highest volcano, and close to the state boundary between Puebla and Veracruz. The Las Cumbres caldera was originally believed to be an explosion super-crater, but geologists now think that it was created due to the partial collapse of the eastern flank of the original volcano, between 40,000 and 350,000 years ago. The collapse of the side of Las Cumbres produced a huge debris avalanche (total volume estimated at 80 cubic km, which extended up to 120 km in the direction of the Gulf of Mexico.

Lake Alchichica

According to Dra. Esperanza Yarza de la Torre in Volcanes de México (UNAM; 1984), Lake Alchichica in the Oriental Basin near Puebla occupies another caldera. The basin has several shallow lakes, known locally as axalpazcos (“sandy basin with water” in the indigenous Nahuatl language). These occupy shallow craters (or in one case a caldera) and are largely sustained by ground water. The largest of the lakes, in a caldera, is Lake Alchichica, which has a diameter of 1888 meters, an area of 1.81 square km, and lies at an elevation of 2320 meters above sea level. The rim of the caldera rises 100 m above the lake level. The lake is used for irrigation. This lake is claimed to be Mexico’s deepest natural lake with a maximum depth of 64 meters, and a mean depth of 38.6 meters.

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  • Use the site’s tag system (left hand side of the page) to find lots more posts about Mexico’s volcanoes, geology and landforms.
Jul 062013
 

Popocatepetl Volcano (“Don Goyo” to the people living in its shadow) continues to erupt. On 4 July, several airlines, including American Airlines, US Airways, Delta Airlines and Alaska Airlines suspended operations to and from Mexico City for several hours, resulting in numerous cancelled flights.

Mexico’s National Disaster Center (Cenapred) provides daily updates (in both English and Spanish) on the volcano’s activity. The Volcanic Alert Level was raised today (6 July) to Yellow Phase 3. This includes:

  1. Access is restricted within a radius of 12 km from the volcano’s crater. Permanence in this area is not allowed.
  2. The road between Santiago Xalitzintla (Puebla) and San Pedro Nexapa (Mexico State), including Paso de Cortes, is open only to authorized traffic.
  3. Civil Protection authorities maintain preventive procedures, according to operative plans.
  4. People are advised to follow guidelines provided by official information bulletins.

There are only two higher levels (both described as “Alarm” rather than “Alert”): Red Phase 1 and Red Phase 2.

Since our last update in March, several spectacular images of the volcano have been released.  Activity increases every two or three weeks, as the following brief reports, based on the Cenapred daily updates, reveal:

8 May – Ash rose 3000 m above the volcano before falling on several municipalities in the states of Puebla and Tlaxcala. Residents were advised to sweep it up without using any water to prevent the ash from sticking together and blocking drains. Mexico City’s international airport was closed to flights for a short time.

14 May – Eruptions continued, accompanied by an increase in seismic activity. The Alert Level was raised to Yellow Phase 3 for several days, with evacuation plans about to be implemented. A dome of lava, about 350 m across and 50 m thick, had formed in the crater, prior to being destroyed in an eruption which formed a 3000 m high ash cloud and sent incandescent fragments (“volcanic bombs”) up to 1000 m from the crater. The volcano’s activity subsided within days and the alert level was reduced to Yellow Phase 2.

17 June – A month later, another explosion (see photos) sent ash more than 4000 m into the air, and threw volcanic bombs up to 2000 m from the crater, starting a series of minor wild fires. Winds blowing towards the northwest carried ash towards the south-eastern section of Mexico City. A week later (24 June), minor amounts of ash fell in eight municipalities in the state of Mexico: Amecameca, Tlalmanalco, Temamatla, Cocotitlán, Ozumba, Atlautla, Ecatzingo and Chalco. The local authorities reported no damage, but reminded residents, among other things, to avoid wearing contact lenses if at all possible. The next day (25 June), ash fell on some southern and eastern parts of Mexico City. Three international flights scheduled to land in Mexico City airport were diverted to Querétaro airport.

The typical sequence of activity is shown in the photos. First, pressure from molten rock underground (magma) leads to the formation of a dome of lava in the summit crater (photo below).

Lava dome building in crater of Popocatapetl Volcano

Lava dome building in crater of Popocatapetl Volcano

These domes eventually either collapse or are destroyed by explosions (photos below) that lessen the pressure beneath the surface.

NasaPopocatapetl Volcano erupts, 17 June 2013

Popocatapetl Volcano erupts, 17 June 2013

Following the explosion (shown by the satellite image below), a new dome begins to form, and the cycle of eruptive activity continues.

Geophysicists from the National University (UNAM) who monitor the volcano and analyze its gaseous emissions say that between 1994 and 2008 the volcano emitted 30 megatons (30 million tons) of gases and that it looks set to continue erupting for several years. Popocatepetl is one of the top five volcanoes in the world for emissions of sulfur dioxide. The volcano has added between 6000 and 8000 tons/day to the atmosphere in recent months. Lead researcher Hugo Delgado Granados has been quoted in press reports as saying that the continued gaseous emissions are good news, since the constant releases of pressure should preclude a more explosive eruption.

This YouTube compilation of webcam videos of the volcano provides a time-condensed view of the eruption of 17 June 2013. The 30-second video represents a period of 20-30 minutes, during which the volcano exploded into action, sending a cloud of gases, ash and volcanic fragments high into the air.

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