Jul 182013
 

To make it even easier to search for things on Geo-Mexico, we plan to add the occasional index page as a starting point for the best links relating to particular key topics. Note that all the site can be searched via our categories (right hand navigation bar on every page) and tags (left-hand navigation bar).

Previous index pages on other topics:

The geography of Mexico’s drug trade: an index page

The Basics

Economics:

Drug War Violence and Crime

Drug Money

Other

 

Jul 152013
 

More than a year ago, the World Trade Organization (WTO) sided with Mexico and appeared to finally bring to an end a long-running dispute between Mexico and the USA over “dolphin-safe” tuna. The WTO decision confirmed that the methods used by Mexico’s tuna fishing fleet met the highest international standards, not only for protecting dolphins but also for conserving other marine species.

Dolphin-safe-logoThe USA has now responded by strengthening the rules governing the use of “dolphin safe”, a label first established in 1990. According to Mexican officials, the changes effectively circumvent the WTO decision by establishing two distinct regulatory regimes, one for the Tropical Eastern Pacific Ocean area (where the Mexican tuna fleet operates) and another, much less restrictive, for all other regions.

Mexican officials argue that the second regime, which does not include independent observers, has been unilaterally established by the USA in order to protect its own tuna fleet which uses methods that are not environmentally sound.

Part of the conflict over “dolphin safe” tuna revolved around the very different methods of fishing employed in the two countries. Mexican tuna fishermen use the encirclement method which involves locating tuna by chasing dolphins that swim with the tuna schools. Large purse seine nets are then employed to scoop up the fish. Decades ago, this method did indeed result in many dolphins being caught as bycatch. This led to justifiable outrage from environmentalists and the “dolphin safe” system. It quickly led to Mexico’s fleets employing specially-adapted nets and changes in procedure to ensure that any dolphins accidentally trapped can escape or are released and returned (alive) back to the ocean. According to the best available data, these improvements quickly reduced dolphin bycatch to close to zero.

Most US tuna fishermen, on the other hand, rely on either long-line fishing, in which every species hooked is killed, or employ fish aggregating devices to encourage the tuna to school. Both methods used by US tuna fisherman kill many immature tuna as well as numerous other species, including sharks and marine turtles (especially the critically endangered Pacific leatherback turtles), as well as seabirds (especially albatrosses and petrels).

The WTO agrees with Mexico that the method used by its tuna fleet is the most sustainable of those permitted by the International Dolphin Protection Program, and protects not only dolphins but also avoids the bycatch of juvenile tuna, ensuring the long-term viability of the tuna fishing industry.

The WTO resolution appeared to finally end this acrimonious dispute which had begun thirty years ago and included a US embargo against Mexican tuna which lasted for more than a decade. It meant that Mexico’s tuna fishermen could legally stamp “dolphin-safe” on their exports to the USA, the world’s largest tuna importer, certifying that the tuna had been caught in full compliance with the International Dolphin Protection Program. The revised US rules mean that most Mexican-caught tuna will still not qualify for the “dolphin safe” label.

Mexico’s tuna catch (mainly yellowfin tuna) peaked at 166,000 tons in 2003 when more than 20,000 tons were exported, mainly to Spain, and has since declined to around 115,000 tons. About 20,000 families in Mexico depend on tuna fishing for their livelihood. This figure includes not only fishermen but also those working in associated processing and packing plants. Mexico’s 130-vessel tuna fleet is the largest in Latin America.

The USA-Mexico tuna war is a classic example of a cross-border fishing/trade dispute. The new US regulations mean that the ball is now firmly back in Mexico’s court. Mexican fishing officials were quick to criticize the new rules, but have not yet announced their next move in this long-running saga which looks set to rumble on for quite some time.

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Jul 152013
 

The population of Mexican origin in the USA now totals more than 33.7 million, including 11.2 million born in Mexico and 22.3 million who identify themselves as being of Mexican origin. Mexicans account for 64% of all Hispanics in the USA and 11% of the country’s total population.The changing profile of Mexicans living in the USA.

A Pew Research Hispanic Center analysis of US Census data shows that the portion of the US population that is of Mexican origin is undergoing a gradual transformation. The average age of residents of Mexican origin is becoming younger and average education levels are on the rise. In 1990, only 25% of the Mexican migrants had a high school diploma, compared to 41% today. Even so, among Hispanics, Mexicans have the lowest rate of university education and the highest percentage of people without any health insurance.

Currently, 71% of the Mexicans who live in the USA have lived in the country from more than 10 years, compared to around 50% in 1990. The proportion of migrants that is male fell slightly from 55% in 1990 to 53% in 2010.

The average household income of households with at least one member of Mexican origin was $38,884, compared to a USA-wide average of $50,502. About 49% of families of Mexican origin own their own homes, compared to a 64.6% rate for the USA as a whole.

In terms of jobs, 26.7% of people of Mexican origin living in the USA work in services, 21.1% in sales positions or offices, 18% in transportation, 17.8% in construction, and 16.4% in administration, business, science and the arts

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Jul 122013
 

Mexico is home to six of the world’s seven species of marine turtles, all of which are on the international Red List of endangered or critically endangered species. Participants at last month’s meeting of the Inter-American Convention for the Protection and Conservation of Sea Turtles (IAC), have elected Mexico to preside over the organization for the 2013-2015 period.

Luis Fueyo Mac Donald, the Commissioner of Mexico’s National Protected Natural Areas, says that Mexico will lead the efforts to promote the recovery of sea turtle populations in the Pacific Ocean, a priority because the marine animals are seriously threatened. The intention is to raise public awareness about the turtles’ plight and expand regional cooperation to protect turtle nesting and feeding grounds, as well as migration routes.

Selected marine turtle nesting beaches in Mexico.

Selected marine turtle nesting beaches in Mexico.

The next formal meeting of the IAC members will be held in Mexico in 2015.

In related news, the Central America Fisheries and Aquaculture Organization (Ospesca) has announced that new regulations are now in place to protect sea turtles in Central America and the Dominican Republic. The regulations should greatly reduce the numbers of turtles caught in shrimp nets, which now have to be fitted with Turtle Excluder Devices (TEDs). TEDs are metal grids of bars attached to shrimp trawling nets; they have openings designed to allow larger animals, such as sea turtles, to escape, while keeping shrimp inside.

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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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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.

Main sources:

Want to read more?

  • 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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Jul 042013
 

This post presents a short case study of the dramatic ecocide in the Hurtado Reservoir in Jalisco a week ago that resulted in the sudden death of between 200 and 500 tons of fish.

What?

  • The ecocide killed between 200 and 500 tons of fish
  • 30 local residents were affected by gastrointestinal problems
  • 15 of them required treatment in local health centers
Local fisherman sees his livelihood disappear. Credit: Vanguardia

Local fisherman sees his livelihood disappear. Credit: Vanguardia

Where?

The ecocide occurred in the Hurtado Reservoir (Presa del Hurtado, aka the Valencia Dam) in Jalisco, mid-way between the villages of San Isidro Mazatepec and Bellavista, the location of a sugarcane mill (see map). The reservoir can hold up to 8,000,000 cubic meters of water. The two municipalities involved are Acatlán de Juárez and Tlajomulco de Zúñiga. The most affected community is the small village of San Pedro Valencia (about 300 inhabitants),

Location of Hurtado Reservoir (extract from INEGI 1:250,000 map)

Location of Hurtado Reservoir (extract from INEGI 1:250,000 map)

When?

The first reports were made on 25 June when a local government official in San Pedro de Valencia, in the municipality of Acatlán de Juárez, reported to state environmental protection officials that the water in the Hurtado Reservoir was contaminated with something smelling like molasses. Within 48 hours, officials had identified the source, and had conducted a formal inspection, reporting that the water was dark brown in color and contaminated with molasses.

Why?

According to press reports, an unlicensed firm in nearby Potrero los Charros was using molasses (a by-product of sugarcane mills) as an ingredient to make cattle food. Some of the molasses (melaza) was dumped into the San Antonio stream which carried them into the reservoir.

The problem arose because molasses have a very high biochemical oxygen demand (BOD). This means that they require large amounts of oxygen as they decompose. In this case, they required more oxygen than was available in the water in the reservoir, reducing the water’s dissolved oxygen content, effectively depriving all aquatic life of oxygen. While final results are pending, the fish are believed to have died of oxygen starvation.

Effects

  1. The local fishing cooperative of the Hurtado Reservoir has agreed to accept a moratorium on catching, selling or consuming local fish. The fishermen normally catch and market about 100 kg of fish a day.
  2. Health services are offering vaccinations to local residents and all those involved in the environmental clean-up.
  3. 18 local restaurants are closed until further notice. When they reopen, they will likely have to purchase fish from further away (eg the fish market in Guadalajara) at a higher price than they previously paid for local fish
  4. About 100 fish traders in nearby towns (including Tala, Acatlán de Juárez and Villa Corona) have lost a source of income.

Responses

  1. Within 48 hours of the first report, authorities had ordered the business responsible for the pollution to take immediate remedial action. Meanwhile, authorities began to clean up the dead fish. The fish are being buried in a 30 meter by 2 meter trench about one km away from the lake.
  2. Federal officials from the National Water Commission and the Environmental Secretariat were quickly on the scene; they promised access to federal financial assistance.
  3. Most of the clean up was carried out by about 100 local fishermen and volunteers, including firefighters.
  4. State health officials have closed the 18 small fish restaurants near the lake until further notice
  5. Local officials are also cleaning up the storage area, using tanker trucks to remove an additional 8,000 tons of molasses for appropriate disposal elsewhere.
  6. The municipality of Tlajomulco has issued the owner of the company with a fine of about 1.5 million pesos ($120,000) and further legal action is underway.

Remediation

  • Environmental expert Gualberto Limón Macías estimates it will take between two and four years to rehabilitate the reservoir. The priority is to re-oxygenate the water, possibly using solar-powered pumps, and seed the reservoir with young fish.
  • The University of Guadalajara has promised to arrange for a team of experts to provide specialist advice about how best to rehabilitate the lake.

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Jul 012013
 

The El Macayo dam on the border of Tabasco and Chiapas states in southern Mexico was officially inaugurated last month. The 90-million-dollar dam, which has been under construction for a decade, is designed to regulate flow along the River Grijalva (aka Mexcalapa and Carrizal) that flows through the city of Villahermosa in Tabasco.

Presa El Macayo (Chiapas/Tabasco)

Presa El Macayo (Chiapas/Tabasco)

The city and surrounding settlements have suffered severe flooding many times in recent years, and the El Macayo dam should bring some much-needed relief to around 700,000 people who live in the areas of greatest risk..

Villahermosa floods 2007

A flooded district of Villahermosa, the capital of Tabasco state in 2007. Photo: AFP

Why does the state of Tabasco have a high risk of floods?

The Grijalva–Usumacinta river system is one of the world’s largest in terms of volume. It is easily the river system with the greatest flow in Mexico. It is essentially a double river, with two branches of similar length which both start in Guatemala. Each branch flows about 750 km (465 mi) through Chiapas before they unite in Tabasco about 25 km from the Gulf of Mexico. Each of the two branches has a flow of about 14% of Mexico’s total. The flow of the combined Grijalva–Usumacinta River is about twice that of the Missouri River in the USA.

The state of Tabasco itself receives an average rainfall three times higher than Mexico’s national average rainfall, and accounts for 38% of the country’s freshwater.

Given these conditions, it is not surprising that the state of Tabasco is one of the most vulnerable states for flooding in Mexico. The UN’s Economic Commission for Latin America and the Caribbean has estimated that the state suffered around $4.5 billion in losses from flooding between 2007 and 2011.

Integrated Hydrology Plan

The dam is only one small component in an Integrated Hydrology Plan that is has been designed by the National Water Commission, Conagua. The agency has been assigned more than $110 million this year to complete existing hydrology-related infrastructure projects and update flood protection plans. The previous government spent $640 million to begin a flood management program for the state; this included building flood prevention infrastructure, dredging the major rivers and constructing flood-alleviation channels.

Arturo Núñez, governor of Tabasco state, says that the state’s flood management program should include the relocation of residents currently living in the most vulnerable areas, as well as reforestation of the drainage basins, continued regular dredging of the main rivers, and a reorganization of irrigation systems.

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Jun 292013
 

Only days after we published our third post about the Primavera Forest, near Guadalajara, we were alerted to an excellent 9 minute video animation of how the area was formed. This short video about “The Exciting Geology of Bosque La Primavera” was produced by geologist Barbara Dye during her stint as a Peace Corps volunteer in Mexico.

The video can also be viewed in Spanish:

Dye has also written a beautifully-illustrated 72-page guide (in Spanish) to the geology of the Primavera Forest, entitled “La Apasionante Geología del Área de Protección de Flora y Fauna La Primavera.

Previous posts about La Primavera: