How the Springs Work
All the thermal springs the Banff Spring Snail calls home are found along the Sulphur Mountain Thrust Fault, along the eastern facing slope of Sulphur Mountain. The highest elevational spring, the Upper Hot, is found at 1584 metres above sea level. The Middle Springs are at approximately 1500 metres elevation while the four thermal springs at the Cave and Basin National Historic Site are at 1400 metres above sea level.
There are currently several theories explaining how the thermal springs on Sulphur Mountain work. In 1959, scientists thought that the water in the thermal springs on Sulphur Mountain came from Sundance Creek, which is in the valley west of Sulphur Mountain and contains the Borgeau Thrust. By 1972, another theory was proposed that it was actually rain and snow falling on Sulphur Mountain which supplied the springs with water. In the early 2000s, scientists collected water from the springs and at different elevations on the local mountains. By comparing the stable-isotopes in the water, they determined that water in the thermal springs on Sulphur Mountain originates as water falling on the local mountains at an elevation of approximately 2000 to 2100 metres. This helped confirm that the water in the springs is from locally deposited rain and snow but did not determine from which mountain.
For the original rain and snow source theory to work, water would have to filter down cracks and across layers of rock because rocks are layered with an upward slope from east to west as one looks northward from the town of Banff. While there are still proponents of this theory, yet another theory is that rain and snow falling on neighbouring Rundle Mountain is the source of the water. Water infiltrating down through the rocks on Rundle Mountain would flow along the sloping layers of rock, not across the layers.
Regardless of whether the water falls on Rundle or Sulphur, as it sinks into the earth, it begins to warm. At some point, it reaches the Sulphur Mountain Thrust Fault, literally a pipeline to the surface. Scientists have calculated that water flowing from the springs on Sulphur Mountain comes from depths up to 3.2 km below the surface.