Getting to Know Nature’s Hot Tubs

British Columbia has over 85 hot springs, the most of any province in Canada, and many are located in the Kootenays. For Fernie newcomers like myself, the Lussier hot springs are constantly recommended as a ‘must-do’ activity, and for good reason. Located just outside of Canal Flats in White Swan Provincial Park, these beautiful natural springs are right next to the Lussier River, with several pools of varying temperatures. During my visit a few weeks ago I wondered about the science behind these geological phenomena: why does BC have so many hot springs? Where does the heat come from? And what’s up with that eggy smell??

BC: A Hot Spring Hotspot
Unlike normal springs, water in hot springs comes into contact with rocks that have been heated by geothermal heat. Fissures in the ground create a sort of plumbing pathway for rainwater and snowmelt to flow deep down, where the earth is hot. Depending on how far down the water travels, hot spring temperatures can vary: the deeper, the hotter. Depths reached can range from about 600m to 2500m beneath the surface. As a result, temperatures usually range from about 20 to 50ºC. At Lussier Hot Springs the water temperatures vary from 34º-47ºC depending on the pool.

British Columbia has many hot springs primarily because it is located along the epically named Ring of Fire. This is an area that stretches along the coasts of the Pacific Ocean, from the southern tip of South America, up to Alaska, through Japan, and all the way down to Oceania. Along these coastlines, ocean plates are pushed under continental plates causing “subduction zones.” The oceanic plates sink or “subduct” into the mantle, melt, and rise to the top, bringing geothermal heat from the earth’s mantle closer to the surface.

Why is the earth so dang hot?
In general, geothermal heat has two origins: primordial and radiogenic. Primordial heat is what still remains from the creation of the planet 4.6 billion years ago. On the other hand, radiogenic heat is produced by the decay of radioactive elements such as uranium, thorium, and potassium. As these elements break down over time, they release heat. Although this may sound like you’re swimming in a pool of radioactive water, you sadly won’t be picking up any superhuman abilities. The water itself has extremely low levels of radiation and is perfectly safe to swim in. These two heat sources work together to warm up the spring water to that hot tub-like heat that we know and love. 

A home for sulphur munching bacteria.
The eggy scent found at Lussier and many other hot springs is caused by the chemical hydrogen sulphide (H₂S). Sulphates get dissolved from rocks underground as water passes through and, combined with low oxygen conditions, foster the growth of “anaerobic bacteria.” These bacteria don’t need oxygen to survive and instead use sulphate as an energy source, emitting H₂S as a chemical by-product and causing the smell. You can even see these bacteria growing in white filamentous mats in the hottest of the Lussier pools!

Hopefully, you can now appreciate hot springs not only for their beauty and relaxation, but also for the geological journey that the water takes in order to become a hot spring. Next time you’re at Lussier Creek and hear someone wondering how these seemingly magical springs work – you’ll have some answers! 

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