By Carie Birkmeier EBS Staff

Hot springs, also known as thermal springs, are naturally occurring discharges of groundwater that are typically heated by intrusions of magma in volcanic areas. Groundwater that’s fed by rain and melted snow flows underground and seeps into the earth via cracks in its surface. Heated water rises to the surface as a spring and mixes with water in rivers or shallow pools to create a pleasant soaking environment, or natural hot tub.

Geysers are formed in the same way, but the difference between a geyser and a hot spring is that a geyser has an obstruction between underwater chambers and the surface, causing its water to boil underground rather than rising to the surface. These obstructions cause steam to push water up and the change in pressure results in an eruption.

In hot springs, the water is able to move freely to the surface, which allows for a mostly even release of heated surface water. Some hot springs can reach 280 degrees Fahrenheit, meaning that not all hot springs are safe to soak in. There are 61 known hot springs in Montana, ranging from natural springs to soaking pools that have been built for commercial purposes.

A trademark characteristic of some hot springs is their sulfuric smell, which is commonly associated with rotten eggs. Because the hot water feeding into the spring comes from underground, it dissolves and picks up all sorts of minerals and elements along its path to the surface. The elements that contribute to the smell are sulfide compounds, with sulfur giving off the characteristic smell. Some smell more pungent than others. Higher water temperatures allow for more compounds to be dissolved.

The Boiling River, located within Yellowstone National Park just south of Gardiner, is a popular tourist destination in winter and summer seasons alike. NPS PHOTO

One of the most popular natural hot springs in our region is the Boiling River, which is located at the very north end of Yellowstone National Park, south of Gardiner. This hot spring has a maximum surface temperature of 163 degrees Fahrenheit, but mixes with cooler water from the Gardiner River to form a pleasant soaking environment just above 100 degrees, depending on the time of year. Although Yellowstone is an area with a large amount of hot springs, this is one of the few locations within the park where soaking is permitted.

Commercial hot springs pump heated water from below ground into constructed pools and tubs. Most of these places are considered resorts or spas and require a fee for soaking, unlike more remote, undeveloped springs. Many of these commercial spas have different pools that they regulate to different temperatures. Depending on your preference, you can soak in water that’s lukewarm or piping hot.

Do some research on specific springs, especially undeveloped ones, before embarking on a day trip to a hot spring. It’d be disappointing to travel to Nimrod Hot springs expecting a warm soak, only to be greeted with a cool pool with a maximum surface temperature of 70 degrees Fahrenheit! The following map lists popular destinations, both developed and undeveloped, to check out next time you’re on the mission for a relaxing soak.