Clariluz Tapia - Geology 211

Physical Geology 2002

http://www.cenapred.unam.mx

My Classmates' Links:

An Interesting Fact:
During times of war the Spanish would sometimes dig out sulfur from the volcano's insides by lowering someone down to scrape it off. This was very dangerous because of the volcano's activity and gas emissions but sulfur was greatly needed for gun ammunition.

http://www.cenapred.unam.mx

Myths Surrounding Popocatepetl:
There is an Aztec myth that says that Popocatepetl was a warrior who was in love with emperor's daughter named Iztaccihuatl (Nahuatl for "sleeping woman"; Iztaccihuatl is a nearby dormant volcano who's summit is 20km away from that of Popocatepetl's). Popocatepetl, who had gone away to war, was just returning after his victory when enemies sent word that he had been killed. Princess Iztaccihuatl, not knowing that he was still alive, died of grief before his arrival. The legend goes that Popocatepetl built two mountains: the first where he placed Iztaccihuatl's body and the second where he stands eternally holding her funeral torch.

http://volcano.und.nodak.edu/

http://www.cenapred.unam.mx

Literature Cited:

http://www.volcano.si.edu/gvp/usgs/#popo
http://www.cenapred.unam.mx
http://www.volcanolive.com/popocatepetl.html
http://volcano.und.nodak.edu/
http://volcanoes.usgs.gov/Products/Pglossary/LavaDome.html

Popocatepetl: A Stratovolcano

Popocatepetl, the Nahuatl name given by the Aztecs to the second highest volcano in Mexico, literally means "smoking volcano". Its name was coined during the Pre-Hispanic era. This volcano (located approximately 19.02N, 98.62W) is about 72km southeast of Mexico City and 43km west of Puebla. Its summit elevation, or the elevation of its highest peak, is 5,426m.

Popocatepetl is classified as a composite cone or a stratovolcano. These types of volcanoes are most commonly located in what is known as the Ring of Fire. That is they are on or near the coasts that surround the Pacific Ocean where subduction is occurring. It has had at lest 14 - 15 recorded eruptions since the Spanish arrival in 1519. Although most recent eruptions have not killed too many people its potential to do so is great.
http://www.cenapred.unam.mx

What are Composite Cones/Stratovolcanoes?
Composite Cone or Stratovolcanoes are volcanoes that reflect what they have erupted which is mostly gas-rich magma with an andesitic composition. This type of magma (which is very viscous or slow to move and is very thick) means that most of the time eruptions are not very violent as compared to those of basaltic and/or rhyolitic compositions (which are not viscous, but very liquid and flowing). That is not to say that once and a while stratovolcanoes never let out a violent eruptions because they have also been known to sometimes emit materials having some basaltic/rhyolitic compositions. In short, Composite Cones are made up of what they have thrown up or let out over time and usually have moderate volcanic activity (when they are not dormant).

http://www.cenapred.unam.mx

A typical Composite Cone has a steep summit (the summit is the highest part of the volcano) that then turn into sides that are less steep and gradually sloping. Its shape is cone-like or conical hence the name Composite Cone. When the volcano is young the cone starts with lava and pyroclastic material (hot gas mixed with glowing ash and pieces of rocks) coming out from the middle or central vent. At his time the lavas are more abundant and flow longer than in more mature Stratovolcanoes, which is one reason for the wider and less steep base of the cone. (Another reason for a broad base of the cone could have to do with lahars or massive mudslides also common in Stratovolcanoes). When the volcano gets older lavas can come out from fissures towards the bottom of the cone. Also material on the summit is coarser and jagged where as material going down the slopes gets finer and finer, flattening the sides.

http://www.cenapred.unam.mx

Some times Composite Cones have developed a U-shaped depression at its summit after a big eruption. Another characteristic usually displayed by Stratovolcanoes is the development of a lava dome. A lava dome is made up of silica-rich lava which is felsic or rhyolitic in composition and very viscous. This lava is pushed through the central vent and creates something like a really hard bubble when the lava hardens. (for more information check out a link at the bottom).

http://volcanoes.usgs.gov/Products/Pglossary/LavaDome.html

Other examples of Composite Cones/Stratovolcanoes are Mount St. Helens (USA), Vesuvius (Italy), Mount Mayon (Philippines), and Fujiyama (Japan).

Currently at Popocatepetl:
Popocatepetl had been dormant for about 5 decades when activity resumed again in 1994. On December 22nd of that year authorities were forced to evacuate 16 villages (about 25,000 people) surrounding the volcano when it spit up about 5,000 tons of hot ash into the sky. Since then the volcano has grown more and more active. There have been frequent small explosions of ash and incandescent materials, which is common in stratovolcanoes. The 1994 eruption has promoted awareness and has spurred scientists around the world to help local authorities and scientists in monitoring the volcano.
This has lead to the creation of a federal agency called Cenapred (which, in English, is the National Disaster Prevention Center). Cenapred monitors Popocatepetl keeping constant observations of variations in gas emissions and seismic intensity. Cenapred has also put surrounding areas within the volcano's reach on "yellow," which is to say that these areas are constantly on alert. If the areas ever get put on "red" then evacuation is imminent. Because these areas are so densely populated this makes Popocatepetl one of the most potentially dangerous volcanoes in the world. (Remember that both Puebla and Mexico City are both extremely populated, Mexico City being the biggest metropolitan place in the world).
The eruption has also promoted studies of the volcano's Holocene history to gain more information of future eruptions and possible impacts on settlements in the neighboring areas. There is a saying that the present is the key to the past, but it is also known that the past can also be the key to future especially when there are reoccurring situations.

This map shows the danger zone of areas surrounding Popocatepetl if an eruption occurrs:

http://www.cenapred.unam.mx

History:
Popocatepetl (also commonly called Popo) has had some pretty violent eruptions in the past complete with a Plinian pulse that created pumice, hot ash or pyroplastic flows, and mudslides or lahars. The biggest of these have taken place between 3195 and 2830 BC, 800 and 215 BC, and 675 and 1095 AD. During each of these eruptions the area of devastation has been a densely populated and important religious site in Mesoamerica. After Each Eruption there has been a trend of re-population within those areas again. This is because the valley or central basin of Mexico has a good temperate climate, is a good geographic location, has fertile soils, and easily accessible water supplies. Popocatepetl over looks this area along with its neighbor Iztaccihuatl who is dormant.

http://www.cenapred.unam.mx

Author: Clariluz Tapia
Creation date: 25/02/2002

Revision Date: 26/03/2002

Send corrections or comments to tapiacl@earlham,edu

[Links to all class members sites will be inserted here.]

This website is part of a Geology 211 class project on Processes in Physical Geology.

Earlham · Geosciences Department · Geociences 211: Physical Geology