Cumbres & Toltec Geology Train – June 9th, 2024

2024-06-05 | CGS Admin

Many of you know and love the Geology Train – the Colorado Geological Survey’s twice-annual partnership with the Cumbres & Toltec Scenic Railroad offering a unique experience observing spectacular geology in Colorado and New Mexico. Our next ride departs on June 9th and tickets are still available!

This June, Nate Rogers, Energy Resources Specialist and Geologic Mapper, and Amy Crandall, Engineering Geologist, will be embarking as geo-docents to assist the crowd with geological information along the way.

We had the opportunity to sit down with Peter Barkmann, Senior Hydrogeologist (Emeritus), to chat about his favorite parts of the Geology Train. While he is unable to make it on the June trip, Peter has been a geo-docent for nearly every Geology Train ride since it began in 2010. You can catch him on the September 8th, 2024 Geology Train.

What is the Geology Train with the Cumbres & Toltec Scenic Railroad?

The Geology Train is operated by the Cumbres & Toltec Scenic Railroad with its start in 2010. This is a special trip on the scenic railroad dedicated to learning about the geology along the route. Initially, it ran once a year in June, but with growing interest by the public and near sell-out for many trips, the railroad added a September trip starting two years ago. The railroad is run as a living museum, striving to maintain the feel of the original operation of the railroad which goes back to the late nineteenth century. It offers many special trips throughout each season that highlight different aspects of the route and operation. The Geology Train has become a highlight trip that the CGS has contributed to since its initiation in 2010.

What is to be expected from a Geology Train ride? Who is it for?

To begin with, spectacular scenery. The Cumbres & Toltec Scenic Railroad truly is a unique ride. Heading west, it takes you from the wide-open San Luis Valley, up through the high desert with lava-capped mesas and deep V-shaped canyons, and then into high alpine, glacier-carved valleys of the Tusas Mountains. It’s a very dramatic change from high desert to high alpine expanses. We top out at Cumbres Pass, which is the highest point on the route. From there we quickly descend into the lush, green Chama Valley.

Along the way we talk about the geologic features and events that led to this spectacular, and varied, landscape. As it gradually climbs heading west, the route passes exposures of basalt and sedimentary fill of the Rio Grande Rift, a vast tectonic feature that we get to view from the mesa tops. Because the railroad grade is less than the eastward dip of the rift, the route passes through progressively older rocks heading west. Once through the rift-related volcanic rocks and sediments, we pass into older ash-flow tuffs, lava flows and volcaniclastic rocks derived from the San Juan Volcanic Field. This vast volcanic field is considered one of the largest clusters of calderas, or supervolcanoes, recognized in the world making this a truly world-class volcanic region. And then, almost halfway through the trip, we hit the Precambrian rock core of the Laramide-age Brazos-Tusas uplift where we walk through the Rock Tunnel. At this stop you can put your hands on 1.7-billion-year-old metamorphic rocks and igneous rocks. After the Rock Tunnel the views open up as the route returns to the volcanic rocks and enters a glacially carved alpine setting. Glaciers once filled these valleys, and we see glacial deposits and large landslide complexes that developed as the glaciers retreated. Later, near the end of the trip, we are rewarded with beautiful views of the Laramide-age San Juan Basin to the south (about 75-55 million years old). As we descend, we pass exposures of folding and faulting related to development of the San Juan Basin and even more signs of alpine glaciation.

Docents strive to talk about the geology in a way that people who are not trained in geology can understand. And the people just really love it—I mean, most of the people on that train are not geologists. We have five to seven docents on board, depending on who is available. Each docent speaks over a train-wide PA system about geologic features at various stops during the trip. But we are also there to just mingle with passengers as we go, talking about what we’re seeing. This trip is for anybody with any curiosity about geology because you really do get to see a pretty remarkable slice of geology.  It’s for anyone!  

What is your connection to the Geology Train and/or the Cumbres & Toltec Scenic Railroad?

My history with the railroad goes back to when I was a little kid, because I grew up in northern New Mexico and my father was a bit of a rail fan. His passion was fly fishing, so we’d come up into this area often to camp and fish. We’d always see the old freight trains chugging over the line, and of course being a kid I was fascinated with them. In about 1967, the Denver-Rio Grande Railroad realized that the days of steam-powered, narrow-gauge railroading were over. My father, being a bit of a rail fan, joined with some other rail fans in northern New Mexico to save the line. They banded together and dreamed and schemed of ways to save the historic railroad. Ultimately, their efforts led to the states of New Mexico and Colorado buying this portion of the line.

Fast forward to my career as a hydrogeologist. I got to know a mine geologist named Rob Benson at a gold mine being developed near San Luis. We bonded talking about the San Luis Valley and San Juan Mountains, and of course I had to talk about the Cumbres & Toltec Scenic Railroad. Rob went on to become a professor of geology at Adams State in Alamosa. At some point as a professor, he made contact with Rich Muth, or Rich reached out to Rob. Rich is another rail fan actively involved with the volunteer programs with the railroad, and he and Rob cooked up this idea of the Geology Train. I don’t know if it had anything to do with Rob and I talking about the Cumbres & Toltec when we were bailing wells together at the mine site or not, but Rob and Rich developed this relationship and put together the idea for the Geology Train. And Rich was involved with the Cumbres & Toltec, so he was able to make it happen. As Rob and Rich were developing the Geology Train concept which required geologist docents, or geo-docents, Rob contacted me. So, I was brought in right off the bat on that first run to help out as a docent, so that’s when I got started with it, and I’ve been with it ever since. Sadly, Rob’s health began to fail, and he gradually pulled back from actively helping with the train and he eventually passed. By default, I have taken on the active tasks helping Rich organize docents for each run. We all miss Rob Benson, and our guidebook is dedicated to him and we pause at the Rock Tunnel to remember him.

Do you have a favorite story from a Geology Train ride?

There are too many wonderful times. But I have to share one from last year that is not directly rail or geology related, but it says much about the atmosphere with the crowd. In line for lunch at Osier I started talking with a man in front of me who had just remarked how much he was enjoying the trip. He didn’t realize I was a docent, so I told him how great it was to hear that compliment. As always, the question comes up: Where are you from? And he said from the San Luis Valley, but then went on to say “Missouri-Kansas.” I remarked “Oh, my father grew up in Leavenworth, Kansas.” And then he went, “That’s where I’m from!” Conversation went on and on about my great uncle who was a doctor and his grandfather who was a pharmacist. We realized they must have known each other. Then after asking where I lived in Leavenworth I replied “No, I lived in Santa Fe, New Mexico.” Next, he remarked, “Oh, I went to Santa Fe, New Mexico as a kid with my grandmother and we stayed with Nina Barkmann.” Pulling the fork with a bite on it out of my mouth I gasped, “That’s my grandmother!”  And then he even remembered being at her house, which was our house, meeting other kids, which would’ve included me! And this is just one of those things, it’s a small world! That’s not a geology story but it’s a personal story of what happens on a trip like this where we’re mingling with many people with so many backgrounds and interests.

Categories & Tags




CGS, geology, RockTalk, third-party