How Do Geothermal Hot Springs Form?
Geothermal hot springs form when groundwater travels deep into the Earth, absorbs heat from the crust, and rises back to the surface carrying dissolved minerals. Along the way, the water moves through ancient rock layers that shape its unique mineral profile. In Glenwood Canyon, this natural process evolved alongside the Colorado River as it carved deeper into the landscape over millions of years. Today, four natural springs feed 16 geothermal pools at Iron Mountain Hot Springs, with temperatures ranging from 89 to 112 degrees Fahrenheit.
How Are Geothermal Hot Springs Formed?
Geothermal hot springs form when groundwater absorbs heat from the Earth's crust and rises to the surface enriched with minerals. Three key ingredients make this possible:
Water, stored underground as groundwater
Heat, held within the rock of the Earth's crust
A pathway, created by cracks, faults, and porous rock
The journey begins when rain and snow seep into the ground through cracks and faults. Gravity pulls the water deeper, where it collects in porous layers of rock and gradually warms.
As the water heats, pressure and buoyancy guide it back toward the surface. It naturally rises through available pathways. By the time it reaches the surface, it carries dissolved minerals gathered during its long underground journey.
This process continues beneath Iron Mountain Hot Springs every hour of every day. The water guests soak in is the final stop in a journey that began deep below Glenwood Canyon.
Where Does the Heat Come From?
The heat inside a hot spring comes from geothermal energy stored in the Earth's crust. The deeper you travel below the surface, the warmer the rock becomes—a natural increase geologists call the geothermal gradient.
Groundwater that circulates deep enough comes into contact with these warmer rock layers and absorbs their heat. In general, deeper circulation produces hotter water at the surface. Some hot springs are heated by nearby volcanic activity, but a volcano is not required for geothermal hot springs to form.
Colorado has no active volcanoes, so the springs in Glenwood Canyon rely on deep water circulation and heat stored within the Earth's crust. The National Park Service geology of hot springs explains how this same process creates hot springs across the country. Beneath Iron Mountain Hot Springs, the Earth's natural heat keeps the water flowing warm year-round.
How Does Water Collect Minerals Underground?
Water collects minerals by dissolving them from ancient rock layers on its underground journey. Warm water can dissolve minerals more readily than cold water, and the longer it remains in contact with surrounding rock, the more mineral-rich it can become.
Every hot spring develops a chemical signature based on the geology it passes through. Limestone, iron-bearing rock, and mineral veins can each contribute something different to the water. When mineral-rich water reaches the surface and begins to cool, some of those minerals may be left behind, creating the colorful deposits often seen around natural springs.
The water at Iron Mountain Hot Springs contains 14 naturally occurring minerals, including iron, sulfate, and magnesium. Iron leaves behind the rust-orange color seen on nearby rock and helped give Iron Mountain its name.
Learn more about the mineral profile and water sources at Iron Mountain Hot Springs.
How Did the Springs in Glenwood Canyon Form?
The springs in Glenwood Canyon shifted with the Colorado River as the river carved deeper over time. Over millions of years, the river cut through layers of rock, reshaping the canyon and influencing where the springs reached the surface. Today, the canyon walls rise high above the Colorado River while the springs emerge near river level.
Water beneath Iron Mountain Hot Springs still moves through ancient rock shaped by this ongoing geological process. Together, the area's hot springs and caves form the only known system of its kind in the Southern Rocky Mountains.
The National Park Service recognized the significance of these connected features in December 2023 through a National Natural Landmark designation shared by Iron Mountain Hot Springs and Glenwood Caverns Adventure Park. Read more about the National Natural Landmark hot springs designation and what makes this landscape so rare.
How Do Four Natural Springs Feed Iron Mountain Hot Springs?
Four natural springs feed 16 geothermal pools at Iron Mountain Hot Springs, with temperatures ranging from 89 to 112 degrees Fahrenheit. The water retains its natural mineral content as it flows into the pools, where guests can find a comfortable temperature or move between cooler and warmer waters.
Set beside the Colorado River, the pools offer views of Iron Mountain and Mount Sopris and an open-air soaking experience in every season.
For a refreshing contrast, three cold plunge pools range from 45 to 65 degrees Fahrenheit, giving guests another way to explore different temperatures during their visit.
What Separates a Hot Spring From a Geyser?
A hot spring releases heated groundwater steadily, while a geyser erupts under pressure at intervals. Geysers depend on narrow underground passages that trap water and steam. As pressure builds, the water eventually erupts above the surface.
Hot springs have more open underground pathways, allowing heated water to rise and flow continuously. Other geothermal features include fumaroles, which primarily release steam, and mud pots, which form where limited water mixes with clay and heated gases.
The four natural springs that feed Iron Mountain Hot Springs follow the calmer pattern, bringing geothermal water steadily to the surface without the pressure-driven eruptions of a geyser.
How Do Inspired Mineral Pools Differ From Natural Springs?
Inspired mineral pools start with freshwater and add precise mineral formulas, while natural springs arrive already enriched. Both contain dissolved minerals, but those minerals reach the water in different ways.
In a natural geothermal spring, water collects its mineral content as it travels through underground rock. Engineered mineral pools begin with freshwater and use carefully developed formulas to recreate the mineral profiles of well-known waters from around the world.
The WorldSprings pools at Iron Mountain Hot Springs follow this approach. Twelve pools are inspired by famous mineral waters, including the Dead Sea, the Blue Lagoon, and Vichy. The Jetted Mineral Spa offers another take on the concept, recreating the mineral profile of Zion Canyon Hot Springs.
This means guests can experience natural geothermal pools and Inspired mineral pools in one location. Our guide to hot springs mineral absorption takes a closer look at how the minerals in both types of water interact with the skin.
Soak Where the Process Still Runs
Geothermal hot springs form underground over long spans of time and surface carrying the minerals of their journey. That natural cycle is still happening beneath Iron Mountain Hot Springs. Water continues to travel downward, warm within the Earth's crust, collect minerals, and rise again to the surface.
Reserve your soak in the geothermal pools in Glenwood Springs and experience the final step of that journey firsthand. Book in minutes. Soak for hours. Feel good for days.
Frequently Asked Questions
Does rain or snow feed hot springs?
Yes. Most hot spring water beginsas rain or snow that seeps underground through cracks and faults. From there, it can spend years—or much longer—traveling below the surface before returning as heated spring water.
Why do some hot springs run hotter than others?
The depth of the water's underground circulation and how quickly it rises helpdetermine its surface temperature. Water that travels deeper is exposed to hotter rock, while water that rises quickly canretain more of that heat.
Can hot spring temperatures change over time?
Yes. Hot spring temperatures can change as rivers, rock formations, and underground pathways shift. The springs in Glenwood Canyon have moved over millions of years as the Colorado River carved deeper into the landscape.
How hot are the pools at Iron Mountain Hot Springs?
Every geothermal pool ismaintained at a temperature between 98 and 112 degrees Fahrenheit. With cooler and warmer options located close together, guests can choose their pools based on personal preference.
Do hot springs freeze in winter?
No. A consistent flow of geothermally heated water keeps hot springs warm throughout the year. At Iron Mountain Hot Springs, winter brings the memorable contrast of rising steam, warm water, and snow-covered canyon views.
Do hot springs exist on every continent?
Yes. Geothermal springs can form anywheregroundwater, heat from the Earth's crust, and underground pathways come together. Colorado alone is home to dozens of named hot springs.
What is the difference between a hot spring and a mineral spring?
A mineral springcontains a high concentration of dissolved minerals at any temperature, while a hot spring is defined by water that rises naturallywarm. The water at Iron Mountain Hot Springs qualifies as both.