On January 30, geography researchers at the University of Guadalajara (UdG) presented a 535-page book on the geoheritage of La Primavera Sierra, describing in detail its “volcanic diversity.”
Some years ago I attended an international conference on geotourism which introduced me to the concept of the geopark. This, I discovered, is a park where people can learn something about the geology of the earth, not from a book but by direct observation.
The United States is a pioneer in geoparks, even though it doesn’t use the name. The Grand Canyon and Yellowstone regularly introduce thousands of people to dramatic geological phenomena which they could scarcely ever forget.
As geoparks began to pop up in other parts of the world, they were organized into a network by Unesco, making it easy for anyone interested in geology to visit sites like Satun Geopark (“the land of Palaeozoic fossils”) in Thailand or Danxiashan Geopark in China, known for its sandstone formations resembling “rosy red clouds.” Today there are 140 of these parks located in 38 countries and they focus on phenomena like granite towers, lava domes, glacier land forms, dinosaur trackways, and places where the earth’s mantle has been pushed right up to the surface. In 2017, the first two geoparks were opened in Mexico. One is the Comarca Minera in Hidalgo with the stupendous basaltic columns of Santa María Regla, which are among the longest reported in the world, with heights greater than 40 meters. The other is the Mixteca Alta in Oaxaca, noted for its spectacularly weathered badlands.
When geography researchers at the University of Guadalajara heard about Unesco’s Global Geoparks Network, they had the same realization that I had, that right here in Jalisco – just next to Guadalajara, in fact – we have another site ideal for creating Mexico’s third geopark. La Primavera Sierra is a perfect candidate because it is so much more than just a forest. It is, in fact, the place where magma has been churning for 140,000 years, resulting in a gigantic explosion that took place 95,000 years ago, throwing 40 cubic kilometers of volcanic ash and rubble into the sky, creating a huge hole which geologists call La Primavera Caldera. This giant bowl filled with water and became a lake for maybe 15,000 years. Continued thermal activity deep below the caldera eventually pushed upwards, draining the lake and creating the hilly forest now known as Bosque La Primavera.
UdG professors Luis Valdivia, Lucía González and Hildelgardo Gómez understood that the dramatic history of La Primavera Caldera is “written” on its high canyon walls and can be understood by anyone, if a geologist simply points at what is there for all to see. They were familiar with La Primavera’s hot rivers, fumaroles, obsidian deposits, giant blocks of pumice and the curious rock formations known as Toba Tala. These researchers also realized that creating a geopark is a slow process involving politicians, the public, and private enterprise and that none of these were likely to make a move without solid documentation backing up the claims of people like me, that La Primavera Caldera has interesting and unusual features that make it worthy of geopark status.
The result was a formal research project to investigate and document the volcanic diversity of Sierra La Primavera. This project was formally announced in a press conference held in 2015. I was fortunate enough to be invited along on many of these researchers’ subsequent forays into the hills and canyons in and around the Bosque and I can assure you I learned something new on every trip.
For me, the most memorable of these excursions were those in search of “chimneys,” perhaps the most interesting of the many formations of Toba Tala. Chimneys in the woods, you say? The first time we saw them, we thought they were cut tree trunks, except for the fact that they were solid stone and did not look at all like petrified wood. Then one day we found some of these “tree trunks” on a hillside scraped by road construction. Here we discovered that what we had been seeing were only the tips of very long cylinders of rock. When we sent photos off to geologist friends, they explained that these cylinders were called “fossil fumaroles” because they had been created long ago by water vapor bubbling up through a flow of hot, volcanic ash, changing the composition of the ash and strengthening it, converting the path of the fumarole into a cylinder harder than the ash around it. These formations are very common on the west side of the Primavera Forest, where the Macrolibramiento (outer city ring road) construction revealed many 12 meters long. It was a pleasure to track down these formations in the company of investigators from the UdG.
The title of the new book by the university researchers is “Diversidad Volcánica y Geopatrimonio en la Sierra La Primavera.” Because it is in Spanish and mostly written in the language of various earth sciences, it is unlikely to appear on a list of this year’s bestsellers. However, with this hefty tome in hand, friends of La Primavera Forest will find it easier to make a case for inclusion of this Protected Area in Unesco’s Global Geoparks Network.