Not long ago, I received an invitation to participate in the Third Global Conference on Geotourism. I wanted to go, but there was a slight hitch: the meeting would be held in Muscat, Oman, 15,000 kilometers from Jalisco. Miraculously, my transportation problem was solved when Casa San Matias, the people who make Pueblo Viejo Tequila, offered to pay for my plane ticket. That left only one small question I still needed to answer: exactly what is Geotourism?
Twenty-five years of exploring the most remote nooks and crannies of western Mexico had convinced me that this part of the country is extraordinarily rich in all kind of natural attractions, such as the Crater Lake of Santa Maria del Oro, the spectacular deep canyons of the Rivers Santiago and Verde, Colima’s rumbling Fire Volcano, the utterly charming waterfalls and pools of Los Azules, near Tequila and, of course, the placid waters of Lake Chapala. Eventually I discovered that we find so much biodiversity here thanks to the fact that Mexico’s five big ecosystems just happen to converge in what I now call The Magic Circle around Guadalajara.
So I naturally figured that the Magic Circle would be a perfect candidate for geotourism, which, I assumed, meant tourism aimed at attractive geological features—of which this area has no end.
That’s what I thought, but when I began to do a little research on the subject, I discovered that certain geotourism sites in the world have been designated “geoparks” by UNESCO and that most of these sites are either unique in their own right or extraordinarily suitable for teaching ordinary laymen the geological workings of our planet.
I brought up the subject with Canadian geologist Chris Lloyd, who immediately suggested I probably meant a site like Gros Morne National Park in Newfoundland, Canada, where people can visit the remnants of a mountain range formed 1.2 billion years ago and can actually touch the deep ocean crust and the very mantle of the earth itself, which has been thrust up to the surface in this unique spot.
“OK,” I said. “I see that not every cave or canyon is worthy of becoming a geopark, but can you think of any place in western Mexico that is—geologically speaking—rare and at the same time suitable for demonstrating geological processes to the Man on the Calle?”
Lloyd looked at me and said, “John, you don’t have to go anywhere to find a site like that. All you have to do is step out your door and walk down the street.”
Thus, did I discover that I live right on the edge of what geologists call The Comenditic Dome and Ash Flow Complex of Sierra La Primavera. “Geologists come here from all over the world to see the Primavera Caldera,” said Lloyd, “but they usually study it from the western extension of Mariano Otero Street. Actually, the arroyo right here at the edge of Pinar de la Venta is much better for understanding the creation of the Giant Pumice Blocks, which, of course, only occur in a few places in the whole world.”
Giant Pumice Blocks? A potential geopark in my own backyard? “It could only happen in Mexico,” I said to myself as I walked with Chris down to the Río Seco, a deep arroyo which separates Pinar de la Venta from the Primavera Forest. Soon we stood at the base of a vertical canyon wall about 50 meters tall. “Welcome to the Primavera Caldera,” intoned Lloyd.
I learned that 25-30,000 years ago, there were a series of pyroclastic eruptions here – probably Mt. St. Helens style – which shot out sideways from their source and deposited ash and other materials into the lake which occupied this Caldera for some 10,000 years. The most wonderful thing about our walk was that Lloyd had only to point at the cliff face before us, where I could easily see the fine, parallel layers of lake sediment, above which there was a thick band of totally different material: ash and pumice which had fallen into the lake and eventually sank to the bottom.
While in most parts of the world pumice occurs as small, featherweight stones only a few centimeters in diameter, the Primavera’s Giant Pumice Horizon is full of enormous blocks of the stuff, typically from four to six meters across. The big plus of seeing these layers from the edge of Pinar de la Venta is that you only have to walk up the Río Seco 100 meters before you actually find yourself inside the Giant Pumice Horizon, where you can pick up monstrous pumice boulders and toss them into the air. Here you can also examine at close hand the contact point where the pumice blocks came to rest on the old lake sediment and deformed it. Lloyd says the giant pumice blocks were probably ejected into the air at the Bugambilias side of the Caldera, fell into the lake and may have been blown over to the Pinar side by the wind. The amazing thing is that the entire scenario of these past events are recorded on the canyon walls, obvious to anyone with a geologist’s eye or – like me – lucky enough to visit the place with a geologist at their side.
Hopefully, the folks attending the Global Geotourism Conference in Oman will be as impressed with the Giant Pumice Horizon as I was. Stand by for my report on the event, coming soon.
How to get there
Take Avenida Vallarta west out of Guadalajara. After about ten kilometers, make a U-turn in the town of La Venta, go back about a kilometer, and turn into Pinar de la Venta’s Gate Number Two (West Gate). Go south and the cobblestone road will take you around the perimeter of Pinar. About ten minutes from the gate, you’ll come to the very first right turn possible. Turn right here and almost immediately take another right. Go downhill and when you come to a road going off to the left, park. Walk south down this road for one minute and you’ll be standing on the edge of the Río Seco, with a geologically informative wall right in front of you. To see a lot more, follow the dry riverbed “upstream” (to your left). Driving time from the Periférico to the parking spot: about 30 minutes.