Why does Colorado have so many hot springs?
Colorado is home to nearly 100 known spots where groundwater rises to the surface, either naturally or through human intervention. People within the state and from across the state come to enjoy a relaxing soak each year. This represents roughly 5.8% of all hot springs in the US.
But why does the Centennial State have so many hot springs, and why are none located in the eastern half? In this article, we will explore how Colorado got its hot springs.
Where are Colorado’s hot springs located?
Colorado’s hot springs are located in the Western half of the state. This is because of the geography and the geology.
“In the case of Colorado’s western half,” writes Colorado Public Radio, paraphrasing Shemin Ge of CU Boulder, “the geothermal gradient is higher, meaning the temperature is hotter closer to the surface…That is why there are a large number of hot springs on the Western Slopes.”
All hot springs are created by geothermal activity: heat from beneath the crust, Earth’s outer layer. When cracks in the crust open, heat from magma (and sometimes magma itself) rises closer to the surface.
These cracks emerge as the Earth’s tectonic plates shift. In some places, they create volcanoes and earthquakes, and in Western Colorado, they create hot springs.
What causes hot springs to form?
Hot surfaces underground cause hot springs to form when they come into contact with groundwater, heating it. Cracks and fissures in the Earth’s crust allow magma to travel closer to the surface. Water that comes into direct contact with magma or rocks heated by magma will begin to steam.
Because of this high temperature, minerals can easily dissolve into the heated groundwater, similar to how hot water steeped in tea leaves produces tea. The mineral composition will depend on the rocks or the magma that heat the water.
Geothermically-heated water will remain underground unless there is either a natural opening or enough pressure for the steam to force an opening. In the latter case, you get geysers; in the former, you get hot springs.
Water can easily lose its temperature as it rises to the surface. Water will cool when it comes into contact with upper layers of rock, which lack a heat source either from the magma or the Sun.
Groundwater comes from water that soaks through the surface of the Earth. Water that remains near the surface will evaporate and return to the atmosphere. Water falling deeper into the soil becomes part of a layer known as an aquifer.
How many hot springs are there in Colorado?
We do not know precisely how many hot springs there are in Colorado; however, the Colorado Geological Survey reports that the state has 93 thermal areas. A “thermal area” comprises natural hot springs, augmented natural springs, and wells (such as Colorado hot springs pools).
Where does the water in hot springs come from?
Water from aquifers can last for thousands of years or may need to be replenished, depending on a number of factors:
- How large the aquifer is – Aquifers vary in size, and size is measured in volume. According to the USGS, small aquifers are only few acres in area and a few feet thick.
- The type of aquifer – Geologists classify aquifers according to a variety of different factors, but the three main types of aquifers are unconfined, confined, and perched.
- The location of the aquifer – Specifically, the location relative of the surface and other source of water.
- How water travels in and out of the aquifer – Unless there is a heat source, the main forces acting on groundwater are gravity, the rotation of the earth, and resistance from rock. The openings in the rock — whether it’s fissures (cracks) in larger rocks or tiny openings between sediment will determine where the water comes from and where it goes to.
- The type of rocks in the aquifer
- Human use of aquifers, both pumping water in and out – Humans use groundwater for a number of different purposes, including the creation of hot springs pools. Pumping groundwater in or out of an aquifer can determine whether the source lasts, and whether the surface sinks because of it.
This is why proper water management is key to keeping local aquifers properly “charged.”
Where can I enjoy Colorado Hot Springs?
At Avalanche Ranch, we have three hot springs pools heated by Colorado’s natural geothermal features. Come enjoy a relaxing day or a relaxing stay at one of the state’s hidden gems in the Rockies.