Exploring the Volcanic History of the Upper Arkansas River Valley
The Upper Arkansas River Valley in Colorado is famous for its towering peaks, rugged canyons, and some of the best whitewater rafting in the country. But beneath the thrilling rapids and breathtaking landscapes lies a dramatic volcanic history that helped shape the valley as we see it today. Since it’s National Volcano Week, let’s dive into the fiery past that formed this incredible region—and how you can experience it firsthand on the Arkansas River.
A Land Born of Fire
Millions of years ago, the Upper Arkansas River Valley was shaped by powerful volcanic activity. One of the most significant events was the eruption of the Thirtynine Mile Volcanic Field, a massive system of volcanoes that was active around 35 million years ago. These eruptions blanketed the region in volcanic ash and lava, creating the foundation for the valley’s rugged terrain.
The Mosquito Range: A Volcanic Legacy
On the eastern side of the Arkansas River, the Mosquito Range tells another piece of this volcanic story. Unlike the Sawatch Range to the west, which was primarily formed through tectonic uplift, the Mosquito Range contains large deposits of volcanic rock and ash from ancient eruptions. Over millions of years, erosion and glaciation carved through these formations, helping create the dramatic cliffs and steep slopes that define Browns Canyon today.
Browns Canyon: A Rafting Paradise Shaped by Volcanoes
One of the best places to see the impact of this volcanic history is in Browns Canyon National Monument. As the Arkansas River flows between the Sawatch and Mosquito Ranges, it cuts through layers of ancient rock, exposing the story of past eruptions. The rugged granite formations you see while rafting through Browns Canyon are the result of both volcanic deposits and the relentless power of water over time.
When you raft with Monumental Expeditions, you’re not just experiencing world-class whitewater—you’re traveling through millions of years of geologic history. As you paddle through thrilling rapids like Zoom Flume and Seidel’s Suckhole, look around at the towering rock walls that line the river. Our guides love sharing the fascinating story of how volcanoes, glaciers, and the Arkansas River all worked together to shape this incredible landscape.
Join Us this Spring and Summer on the River
This spring and summer is the perfect time to explore the fiery history of the Upper Arkansas River Valley. Gorgeous scenery and fun splashy rapids, rafting through Browns Canyon is a one-of-a-kind way to connect with the region’s volcanic past.
Book a trip with Monumental Expeditions today and experience the power of nature—both past and present! Let’s make some waves in a valley shaped by lava and water.