Weather and Climate of Oaxaca

Located 15° north of the equator, a tropical savanna climate dominates most of Oaxaca, blessing the state with mild temperatures year round.  Due to changes in elevation throughout the state, there are small regions in which the local climate is dictated by altitude, but the majority of Oaxaca experiences distinct wet and dry seasons with moderate annual and daily temperature ranges.

This climograph of Oaxaca exhibits the distinct November-March dry
 season and the April-October wet season. Temperatures remain relatively
 constant year round around 28° C (80° F).

At the end of the 1997 wet season, the climatic mild weather was temporarily disrupted when a category 4 hurricane made landfall on Puerto Angel, Oaxaca, devastating much of the coastal regions of the state. Hurricane Pauline developed 250 miles off of the coast of Huatulco, Oaxaca out of a tropical wave (NOAA, 1997).  This convergence along with water vapor from the tropical ocean, a sea surface temperature of roughly 30° C, and a strong Coriolis effect north of the equator were all factors contributing to the formation of a group of thunderstorms over the pacific ocean.  These thunderstorms then traveled eastward, developed into a tropical depression, then into a tropical storm, and finally into the hurricane that destroyed much of the southern coast of Mexico (NOAA, 1997). 

Satellite imagery of Hurricane Pauline off the
coast of Oaxaca, Mexico

This image shows that Hurricane Pauline
 developed over the Pacific Ocean, made
landfall on the southern coast of Oaxaca,
and traveled north-west along the
coast of Mexico before dissipating. 

Many of the coastal communities affected were indigenous, undeveloped areas, giving Hurricane Pauline an easy target for destruction.  Wooden huts were destroyed leaving tens of thousands of people homeless and killing at least 110 (CNN, 1997).  In addition, Hurricane Pauline further contributed to the deforestation problem in Mexico by destroying 6-7 million trees, leading to future mass wasting events (Barkin & Pailles, 1998).

Hurricane damage to Playa Zipolite  

References:

Barkin, D., & Pailles, C. (1998). Water as an instrument for sustainable regional development. Retrieved from http://ag.arizona.edu/oals/ALN/aln44/barkinfinal.html

CNN. (1997). U.s., mexico to discuss hurricane pauline aid. Retrieved from http://articles.cnn.com/1997-10-13/weather/9710_13_hurricane_1_bottled-water-acapulco-mexican-officials?_s=PM:WEATHER

NOAA. (1997). Hurricane pauline - october 3-10, 1997 . Retrieved from http://www.hpc.ncep.noaa.gov/tropical/rain/pauline1997.html

Mass Wasting of Oaxaca

Of the several different geographical regions in Oaxaca, the mountain ranges specifically are covered by lush forests of a diverse range of plant species. The high density of vegetative ground cover make this region a perfect example of a transport limited landscape.  In this area, the rate of transport of weathered material limits the rate of erosion, as opposed to in a non-vegetative weathering limited landscape, where the rate of rock decay limits the rate of erosion.  

The town of Tlahuitoltepec was built on the steep slopes of
a transport limited landscape. 

Liquefaction occurs when extensive
saturation increases the water filled
spaces between particles, decreasing friction
that normally holds sediment together.

In September of 2010, record rainfall in conjunction with previous deforestation led to a devastating mass wasting event in the town of Tlahuitoltepec, Oaxaca.  Transport limited landscapes are, by nature, permeable slopes as they must provide a medium through which plants can absorb water and nutrients.  By removing vegetation that normally limited the downslope movement of weathered material, the landscape became even more susceptible to liquefaction, allowing material to flow.

This photo of the Tlahuitoltepec mudflow exhibits thixotropic material flowing
downslope due to gravity.

With its swift speeds, the Tlahuitoltepec
mudflow was capable of carrying
cars in its flow.

Mudflows can be incredibly devastating to communities that lie in their path. While mudflows generally carry mostly clay and silt particles and not much rock content, they are still extremely dangerous and can travel at speeds ranging from 10-30 miles per hour. With their viscous properties and high velocity, mudflows are capable of swallowing entire villages. The mudflow of Tlahuitoltepec burried 80% of the town and killed 32 people.

 

Citizens, police, and military worked day and night to rescue victims
trapped by this geographical disaster.

References:

Bricker, K. (2010, September 29). Corruption and deforestation caused oaxaca's mudslide disaster. Retrieved from http://upsidedownworld.org/main/mexico-archives-79/2712-corruption-and-deforestation-caused-oaxacas-mudslide-disaster

CBN News. (2010, October 01). Mexico mudslide death toll raised to 32. Retrieved from http://www.cbn.com/cbnnews/world/2010/October/Mexico-Mudslide-Death-Toll-Raised-to-32-/

Shifting the Landscape

Home to many indigenous people, the Sierra Madre del Sur mountain range runs along the coast of Oaxaca and is one of three main mountain ranges found in the state.  Due to its location on the border of the North American and Cocos tectonic plates, we are lead to believe that it formed through an oceanic and continental crust convergence.  Upon collision, the denser composition of the oceanic crust of the Cocos plate caused it to subduct beneath the less dense continental crust of the North American plate.  The friction from this interaction created extreme heat, and along with tremendous pressure, melted the oceanic crust and lithosphere, which eventually cooled, moved to the surface, and created the Sierra Madre del Sur.

    

Oceanic - Continental Convergence

Tectonic plate map displaying the
 subduction zone along the Mexican coast

This image of the Sierra Madre del Sur exhibits a fault line
and scarp due to extension faulting

At the base of the Sierra Madre del Sur, La Punta del Cometa overlooks the Pacific Ocean.  This rock formation exhibits the distinct layers of clastic sedimentary strata, which is formed by the compaction of eroded and weathered rock sediments. 

La Punta del Cometa
In the center of this picture, a possible fault line can be seen.
Hypothetically the lighter, felsic metamorphic or igneous
rock was uplifted in compression, creating a reverse fault. 

Not only do these geographical landmarks serve as tourist destinations, the mountains of the Sierra Madre del Sur are also home to many small scale farmers.  While some grow native produce such as coffee and sugar cane, the high demand of drugs from cartels persuades many farmers to grow opium and marijuana.  The seclusion and vastness of the landscape of the Oaxacan mountains provide farmers with a safe place to cultivate the poppy plant, which cannot thrive below 1000 meters. With elevations ranging from 1500 - 3500 meters, the poppy plant can grow in abundance anywhere in the mountain range. While this is monetarily beneficial to the farmers, it has a devastating impact on the civilians of Mexico who are suffering from decreased food supply and tourism, and increased violence and drug use (Humphrey, 2003).

References

Humphrey, C. (2003). Narcotics, Economics, and Poverty in the Southern States. Retrieved from http://lse.academia.edu/ChrisHumphrey/Papers/292223/Narcotics_Economics_and_Poverty_in_the_Southern_States

Introduction

Hello everyone! This blog is a collaboration of work by Melissa Skinas and Andrew McSherry.  We share a love for traveling, hiking, and scuba diving, so we decided to pick a location in which we could hypothetically partake in these activities.  We landed on the decision of blogging about the southern Mexican state of Oaxaca.  Neither of us have travelled to this beautiful region, but it is a destination we both hope to someday experience. 

We chose Oaxaca because it is blessed with a wide variety of amazing geographical features that were particularly interesting to us. From the deepest cave in the Americas to lush rainforests, beautiful beaches, and several converging mountain ranges, this state has plenty of geographical wonders to learn about and explore. As we learn more about geographical forms and processes in Geography 1202, we will be applying these concepts to the landscapes of Oaxaca, Mexico. 

Hierve el Agua - Petrified Waterfalls East of Oaxaca City