The Springs

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.

BSscreen-shot-2011-02-11-at-8.24.51-am

Simplified topography of the area around the Town of Banff showing the location of the Sulphur Mountain Thrust Fault and its associated thermal springs. The next map shows a view from the side, a cross section, along the line from the bottom left to the middle right (from Grasby and Lepitzki 2002).

Photo taken from the top of Tunnel Mountain looking southwest towards Sulphur Mountain. The Upper Hot Spring is on the left, the Middle Springs are towards the middle, and the springs at the Cave and Basin are towards the right of the picture.

Photo taken from the top of Tunnel Mountain looking southwest towards Sulphur Mountain. The Upper Hot Spring is on the left, the Middle Springs are towards the middle, and the springs at the Cave and Basin are towards the right of the picture.

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.

BS4098crop

Diagram of 1970s theory on how the thermal springs on Sulphur Mountain work as shown in an Interpretive panel that used to be at the Cave and Basin National Historic Site.

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.

Simplified cross section along the line shown in the previous figure looking northward. Rain falling on Rundle Mountain at between 2000 and 2100 metres sinks into the ground and flows downward along the rock layers until it encounters the Sulphur Mountain Thrust Fault and is propelled to the surface due to underground pressures (from Grasby and Lepitzki 2002).

Simplified cross section along the line shown in the previous figure looking northward. Rain falling on Rundle Mountain at between 2000 and 2100 metres sinks into the ground and flows downward along the rock layers until it encounters the Sulphur Mountain Thrust Fault and is propelled to the surface due to underground pressures (from Grasby and Lepitzki 2002).

Next Page – Recent Troubles in Thermal Spring Flows