Volcanoes in our Backyard
by Tara A. Spears
As a country of contrasts and surprises Mexican landscapes vary from pyramids to volcanoes to jungle to gorgeous coastal playgrounds. This geographically diverse country has three thousand volcanoes, 14 of them active, particularly in the central strip that extends from Nayarit to Veracruz. This volcanic range is known as Neovolcanic Axis.
Travel inland from coastal Jaltemba Bay and in just a couple of hours you will view majestic volcanic mountains whose raw power contrasts with the farmlands and villages along the highway. While these giants can cause major catastrophes, there are beneficial effects for the peoples who live near the volcanoes.
The land near the volcanoes has a high degree of fertility due to the nutrients from ash deposits; the high summits of several volcanoes are important for generating flows of water from springs or snow melt. In pre-Hispanic times volcanoes were also sources of raw materials, mainly of rocks of the appropriate hardness to use for sculptures or tools. Obsidian, formed from volcanic flows, played an important role in the daily life of the Mesoamerican societies and that was an element of trade. The pumice, in the form of yellow sand in the subsoil, is volcanic product that the agave plant thrives in.
Pumice is a type of extrusive volcanic rock, produced when lava with a very high content of water and gases is thrown out of a volcano. As the gas bubbles escape from the lava, it becomes frothy. When this lava cools and hardens, the result is a very light rock material filled with tiny bubbles of gas. Pumice is the only rock that floats on water, although it will eventually become waterlogged and sink. It is usually light-colored, indicating that it is a volcanic rock high in silica content. If the lava hardens quickly with few volatiles, the resulting rock is volcanic glass, or obsidian. Pumice and obsidian are often found together. Since pumice is a volcanic rock, and retains its useful properties only when it is young and unaltered, pumice deposits are found in areas with young volcanic fields. Worldwide, over 50 countries-including Mexico-produce pumice products.
Volcan Tequila: According to Geo-Mexico, “Tequila Volcano, which overlooks the rolling fields of blue agaves required to make the liquor, is the home of one of Mexico’s most distinctive geomorpho sites. From the rim of its crater, the most arresting thing about the view is not the green, tree-covered crater itself but the giant monolith with almost vertical sides rising perpendicularly from the middle of the crater floor.”
This well-preserved central spine, known locally as la tetilla (“the nipple”) is quite unusual. It represents the hardened lava which cooled in the central vent of the volcano and which, solid and unyielding, was later pushed upwards by tremendous subterranean pressure. The Tequila spine is one of the best examples of this type formation that exist anywhere in the world.
In the forested area west of Guadalajara lies the only caldera, La Primnavera, that can be recognized in the western section of the Mexican Neovolcanic Axis. A caldera is a volcanic structure that is caused by the collapse of the ground around a volcano. At first glance, it often looks a great deal like a volcanic crater, but the process of its formation is different from that of traditional crater. The key thing to know about craters is that they occur around volcanic vents, which makes standing in one a much more perilous.
The state of Jalisco derives its name from the numerous volcanoes within its boundaries. “Jal is sand pumice, ixco, plane or surface.” says Dr. Enrique Estrada Faudon, of the University of Guadalajara. “All the hills that we see around Guadalajara and Lake Chapala, (Tonalá, La Higuera, the Mexican, San Miguel, the Colli, and Copalita) are extinct volcanoes.” Jalisco is inside a volcanic belt that runs from the Gulf of Mexico toward the Pacific Ocean.
The closest volcano that offers tours is the Tequila volcano, just about three hours away. The drive from Jaltemba Bay to Guadalajara on Cuota 15 provides an amazing bird’s eye view of the volcanic range.
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