Mexico Life
Chorros de Tala waterfall in the Primavera Forest Chorros de Tala waterfall in the Primavera Forest. john pint

Exploring Jalisco’s Primavera Forest

The Lung of Guadalajara is the legacy of a colossal explosion 95,000 years ago

When my wife and I decided to settle down in Mexico we bought a house in a rustic, hilly, mile-high community perched on the very edge of Bosque la Primavera, a protected forest located immediately west of Guadalajara.

The Primavera Forest is huge, covering over 30,000 hectares and is known as the Lung of Guadalajara for good reason.

As an outdoor enthusiast, I was delighted to live in a place where I could walk out the door and hike for kilometers through a pine and oak forest cut by dramatically high and narrow slot canyons, never once bumping into a single human being.

Nevertheless, I didn’t suspect just how extraordinary this forest was until, some 20 years after moving to the area, I attended an international conference on geoparks.

Here I learned that geoparks are places with remarkable geology which is right out in the open, so evident that the most ordinary person could see and appreciate it if someone in the know just pointed it out.

Well, I happened to live next door to a very good geologist and I asked him one day whether there were any sites not too far from Guadalajara with the potential to be geologically educational.

“John,” he replied, “you don’t have to go anywhere to find a place like that. You just have to step outside your door.”

Geologist Chris Lloyd then took me for a walk in a canyon I had strolled through countless times: “Look at that wall. At the bottom you can see tightly packed horizontal lines. Each one represents a layer of sediment formed at the bottom of a huge lake that was located right here for 10 to 20,000 years.”

I learned that the lake was the indirect result of an enormous explosion that occurred in this spot 95,000 years ago, a Yellowstone-type explosion that shot 40 cubic kilometers of volcanic ash and pumice straight up into the air, dimming the light of the sun and leaving behind an 11-kilometer-wide, bowl-shaped hole or caldera that slowly filled with water.

When those tonnes of dust and pumice finally settled back on earth they created a wide swath of volcanic rubble called xalli in Nahuatl, a word transformed into jal by the Spaniards. So the area today known as Jalisco is the “Place of the Jal,” or volcanic sand, which you will find covering the bottoms of most canyons and rivers in the Primavera Forest.

During the lifetime of the lake that filled the Primavera Caldera, small volcanoes formed beneath the surface and began to spew a kind of froth which hardened into gigantic blobs of pumice and floated on the lake like icebergs.

“All that pumice eventually became waterlogged and sank to the bottom of the lake,” Lloyd told me, “and here you can see it on several canyon walls, great blocks of pumice up to eight meters wide.”

Geologists from all over the world have traveled to the Primavera Forest only to study what is now formally known as the Giant Pumice Horizon, but most tapatíos (natives of Guadalajara) have never heard of it and head for El Bosque mainly to soak in its most popular tourist attraction: Río Caliente, the Hot River.

Few people have ever see the spot where Río Caliente literally boils out of a narrow arroyo to begin its journey across the forest to the Chorros de Tala Waterfall where, no longer hot, it is known as Río Salado, the Salty River.

Curiously, Río Caliente is not the hottest river in the Primavera Forest. That honor goes to a small feeder stream only 570 meters long, which features a gorgeous, steaming, hot waterfall called La Cascada Esmeralda for its bright-green algae.

Following this stream back to its point of origin is tricky as you have to cross it numerous times, leaping from rock to algae-covered rock, realizing that, if you make one slip, you could end up cooked like a hot tamal.

Reaching the origin of this Emerald Creek, however, may be worth the risk, because it’s the sort of place you’d imagine the River Styx to have come from, in the middle of Hades, with jets of steam spewing into the air and a water temperature of 70 C.

In Bosque la Primavera you can find rivers both hot and cold, deep slot canyons, majestic mesas, dramatic fumaroles and great deposits of glittering black obsidian, but perhaps the most curious natural formations you will see resemble nothing less than a forest of tree stumps made of stone.

A quick look proves that these truncated cylinders are not petrified wood, but genuine rock. When I first saw them, I imagined the length of these stump-shaped rocks was less than a meter, because that was all I could see.

It never occurred to me that these were just the exposed tips of very long cylinders until the day I spotted one on a roadside where the embankment had been cut away and I saw that it kept going beneath the surface. What might be the total length of these cylinders and how in the world had they been formed?

Once again, I was consulting geologists and this time they told me the story of a place in Alaska called the Valley of Ten Thousand Smokes. “It’s a place where a hot ash flow covered the land, vaporizing surface water. What observers called columns of ‘smoke’ were really columns of condensing steam, bubbling up through the pyroclastic flow. This action alters the ash, eventually hardening it and creating long, vertical, subsurface cylinders called fossil fumaroles.”

Recent roadwork on the outskirts of the forest verified that I what I had first called fairy footstools extend at least 12 meters below the surface and probably a lot more.

Most roads inside the Primavera Forest are open to the public as long as the public is on foot or riding a bicycle. Around 1,000 cyclists take advantage of this every weekend, pouring into the woods from its eastern entrance (Avenida Mariano Otero). They find refreshments, food and tools to fix bikes at Estación Bici, located 2.6 kilometers beyond the point where cars are not allowed to pass.

From what I have seen, mountain bikers — apart from the forest rangers — are the people who know the secrets of Bosque la Primavera best. Many of their trails are posted on the Wikiloc page. In addition, many destinations inside this great forest are described in the book Outdoors in Western Mexico.

The writer has lived near Guadalajara, Jalisco, for 31 years, and is the author of “A Guide to West Mexico’s Guachimontones and Surrounding Area” and co-author of “Outdoors in Western Mexico.” More of his writing can be found on his website.

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