How well do you know Mexico? The geography of Mexico: Quiz 5

 Quiz  Comments Off on How well do you know Mexico? The geography of Mexico: Quiz 5
Jul 292013
 

Welcome to our fifth quiz about the geography of Mexico.

Previous quizzes:

How many of the following can you answer correctly?

If you answer a question incorrectly, you can have more attempts at each question before the answer is revealed.

Good Luck!

[mtouchquiz 5]

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Foreign runners help preserve an ancient Tarahumara tradition

 Other  Comments Off on Foreign runners help preserve an ancient Tarahumara tradition
Jul 262013
 

While generally referred to in English as the Tarahumara, the people’s own name for themselves is “Raramuri“, literally “the light‑footed ones” or “footrunners”. The Tarahumara live in the Copper Canyon region of Mexico and are renowned for their long distance running exploits across some of the world’s most inhospitable terrain. As “modern” life encroaches on the Tarahumara and begins to change their traditional way of life, bringing problems like environmental damage, loss of native lands, and narco-trafficking, will they manage to preserve their ancient traditions such as long distance foot races?

As his contribution towards helping the Tarahumara preserve their foot races, a few years ago, Micah True, an American better known as ultramarathon runner “Caballo Blanco”, who regularly visited the town of Urique in the Copper Canyon, organized a Copper Canyon Ultramarathon. True, who died in 2012, was featured in Christopher McDougall’s book Born to Run. As True hoped, the Copper Canyon Ultramarathon has become an annual event, now known as the Ultra Caballo Blanco that helps maintain the running heritage aspect of Tarahumara culture. The event is usually held in March. Completing the race requires running an estimated 50 miles (80 km) of tracks, trails and and dirt roads, which start and finish in the main plaza of the town of Urique. The event has become the focal point for a cultural celebration.

This short 9-minute Youtube video–Super Athletes of the Sierra Madre–describes the 2009 Copper Canyon Ultramarathon.

Ini additional to some great shots of the rugged scenery and the race itself, the video includes brief references to the history of the area, and details some of the current pressures on the Tarahumara way of life. The Copper Canyon ultramarathon is aptly labelled “the greatest race the world has never seen”. The race is not sponsored and there are no huge monetary prizes for the race winners. Donations are accepted to offset the cost of prizes. Anyone who completes the course within the 14-hour time limit is awarded a voucher for 500 lb of corn. Foreign athletes who compete alongside the Tarahumara in this event donate their corn and prizes back to the community. The event attracts more than 200 runners, with about half of them normally completing the course.

Route of Ultra Caballo Blanco

Route of Ultra Caballo Blanco

This image of the course (from Ultra Caballo Blanco) gives some idea of the terrain in which this race is run. The race starts with a 21+ mile loop up-river from Urique, followed by another 18+ mile loop down-river, and then a final loop (up to the Tarahumara village of Guadalupe Coronado and back down to Urique) adding another 10+ miles to the total distance.

The 12th Annual Ultra Caballo Blanco will take place on March, 2, 2014.

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When does it rain in Mexico?

 Excerpts from Geo-Mexico  2 Responses »
Jul 242013
 

The map below shows a regional division of Mexico by precipitation regime (the amount and seasonal distribution of precipitation). The small graph for each region shows the typical average precipitation amounts for each month of the year. (For example, region A has most precipitation in the first three or four months of the year, and very little after that). The map comes from Ernesto Jáuregai’s 1970 article about wind and water erosion in Mexico (full reference is given below).

Precipitation regimes in Mexico (Fig 2 of Jáuregai 1970)

Precipitation regimes in Mexico (Fig 2 of Jáuregai 1970)

It is clear from the map that the distribution of precipitation across Mexico is very uneven. In general the north and central plateaus are dry while the southeast receives by far the most rain. Parts of Tabasco, Northern Chiapas and Veracruz get over 4000 mm (160 in) of rain a year. This is a direct effect of the onshore north-east trade winds, which collect moisture as they cross the Gulf of Mexico and then deposit it as they reach land.

Average annual rainfall figures conceal great differences from one year to the next. In general, the variability of rainfall is indirectly proportional to the long-term average. This means that areas with low totals tend to experience high variability, greatly increasing their drought hazard.

The map also reveals that there is a marked seasonality to precipitation in almost all of Mexico, with a clear division into a wet and a dry season. Most places get almost all their rain between June and October, while January through May are dry months. Because most rainfall is in the summer months, about 71% of rainfall evaporates soon after falling. This figure can be even higher in urban areas. Only about 26% runs off into rivers and lakes, and 3% seeps down to recharge subterranean aquifers.

One apparent anomaly to the pattern shown on the map is that the extreme north-west corner of Baja California (region A) has a Mediterranean climate where summers are dry and most rain falls in winter. Elsewhere in Mexico winter months are relatively dry. Southern and central Mexico have markedly dry winters, receiving less than 5% of their annual precipitation totals in the first three months of the year. The northern half of Mexico and the eastern coastal strip, including the Yucatán peninsula, have slightly more balanced precipitation, receiving between 5 and 18% of annual totals between January and March.

Map reference:

Ernesto Jáuregai. 1970. “La erosión hidráulica y eólica en México y sus efectos en las estructuras hidráulicas y en los núcleos de población.” UNAM: Boletín del Instituto de Geografía, Vol III, pp 39-60.

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The three main causes of precipitation in Mexico

 Excerpts from Geo-Mexico  Comments Off on The three main causes of precipitation in Mexico
Jul 222013
 

The three basic types of rainfall (convectional, orographic and cyclonic) all play a role in determining the amount and timing of precipitation in Mexico.

Why does it rain?

In Mexico, most precipitation falls as rain, though snowfalls are not uncommon in parts of northern Mexico or at the highest elevations where air temperatures are cooler. For precipitation to occur, the air must first acquire moisture. Warm air absorbs water through evaporation from nearby bodies of water and through evapotranspiration from plants. The amount of water the air holds compared to the maximum amount it can hold at that temperature is the relative humidity. If warm moist air rises, it will cool. As it cools, its relative humidity rises. If relative humidity reaches 100% and condensation nuclei (particles such as dust or contaminants) are present, then water vapor will condense out of the air to form clouds. As clouds develop, water molecules coalesce until individual drops are heavy enough to fall out of the cloud as precipitation. Ice crystals fall as snow, water falls as raindrops, frozen ice pellets fall as hail.

For precipitation to occur, the weight of the individual drops must be sufficient for the effects of gravity to overcome the upwards thrust of the surrounding air. In very unstable conditions where air is rising rapidly, individual raindrops must become much larger before they can fall out of the cloud. The largest raindrops will have traveled up and down inside the cloud repeatedly, gaining size, before they finally fall to the ground. The same principle applies to hailstorms which gather an additional layer of ice for every trip they make inside the cloud before falling.

Though Mexico is considered to be relatively arid, the country as a whole receives an average of about 760 mm (30 in) of rain per year. This is a considerable amount of precipitation, almost exactly the same amount as Toronto, and considerably more than the average for either Canada or the USA.

Annual precipitation in Mexico (Fig .4.3 of Geo-Mexico)

Annual precipitation in Mexico (Fig .4.3 of Geo-Mexico, the geography and dynamics of modern Mexico) All rights reserved.

The three main causes of precipitation in Mexico

Convectional rain is associated with hot afternoons. During the morning, warm air near the surface collects great quantities of moisture. As temperatures increase towards mid-day, pockets of moist warm air are sent upwards, quickly leading to condensation and clouds. As the clouds continue to rise, they cool to the point where precipitation becomes inevitable. Afternoon and evening rain showers result, often heavy and accompanied by thunder and lightening. Convectional rain occurs throughout Mexico but is a summer phenomenon since this is the time of year when solar radiation and ground heating is at a maximum. The effects of convectional rain are enhanced by the presence at that time of year over southern Mexico of the Intertropical Convergence Zone, a broad belt of generally rising air which migrates seasonally either side of the equator.

Orographic rainfall, the second type of rainfall, is associated with mountains. Mountains block the movement of clouds and force them to rise. This has a profound impact on precipitation. As the clouds rise, further condensation occurs and precipitation becomes extremely likely, as they cool to the point where they can no longer hold their moisture. Therefore, it rains a great deal on the windward or wet side of the range. By the time the air passes over the mountain range to the other side, it has lost much of its moisture. As it descends, it warms up and its relative humidity falls, so that there is little chance of any precipitation on the leeward side, known as the rain shadow.

For example, the summer north-east trade winds blow moist clouds from the Gulf of Mexico towards the Southern Sierra Madre and Chiapas Highlands. The eastern side of these mountains receives heavy rainfall. The mountain slopes in central Veracruz, eastern Oaxaca and parts of Chiapas have about 150 cloudy days and get about 2000 mm (80 in) of rain a year. However, the western slopes get only half as much rain and have only 90 cloudy days a year. Orographic precipitation sets virtually all the rainfall and snowfall records, even more than hurricanes. Tenango, Oaxaca is the rainiest place in Mexico; it receives about 5000 mm (16.4 ft) of rain each year. The orientation of mountain ranges is therefore critical to understanding precipitation patterns. The differences between windward and leeward sides of a mountain range can be very dramatic. For instance, El Chico and Pachuca in the state of Hidalgo are only 10 km apart but have 1500 and 400 mm of precipitation respectively each year.

The third type of rainfall is called cyclonic or frontal precipitation. This is the form of precipitation brought by the mid-latitude storms known as nortes, and the tropical storms that sometimes evolve into hurricanes. Nortes occur when the polar air behind a cold front displaces the warmer surface air, forcing it to rise as the cool air pushes its way underneath. At the surface, a sudden drop in temperature and the advent of cold winds marks the passage of the front, followed by several days of overcast skies with light rains or drizzle, onomatopoeically called chipichipis in some areas of Mexico.

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The Mexico-USA tuna war rumbles on

 Excerpts from Geo-Mexico, Updates to Geo-Mexico  1 Response »
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.

Want to find out more?

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Recent trends for Mexicans living in the USA

 Updates to Geo-Mexico  Comments Off on Recent trends for Mexicans living in the USA
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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Mexico presides over Convention for Protection of Sea Turtles

 Mexico's geography in the Press  Comments Off on Mexico presides over Convention for Protection of Sea Turtles
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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Popocatepetl Volcano puts on an explosive show

 Mexico's geography in the Press  Comments Off on Popocatepetl Volcano puts on an explosive show
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

 Maps, Other  Comments Off on The volcanic calderas of Mexico’s Volcanic Axis
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:

  • Gerardo J. Aguirre-Díaz & Fred W. McDowell. 1999. Volcanic evolution of the Amealco caldera, central Mexico. United States Geological Society. Special Paper 334.
  • Esperanza Yarza de la Torre. 1984. Volcanes de México. UNAM.

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.

Images of continued eruption of Popocatepetl Volcano

 Books and resources  4 Responses »
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.

A YouTube compilation of webcam videos of the volcano provides a time-condensed view of the eruption of 17 June 2013. The 30-second video represented 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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Case study of the June 2013 ecocide in Hurtado Reservoir, Jalisco

 Mexico's geography in the Press  Comments Off on Case study of the June 2013 ecocide in Hurtado Reservoir, Jalisco
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

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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