Burning Sulphur
Natural Area

On the east slopes of the Buffalo Head Hills, about 90 kilometres south of Fort Vermillion, bitter-smelling steam and smoke billows from rock debris that has slumped down the hillside. The steam is formed as the underlying bedrock of iron sulphide-rich marine shales oxidizes and produces great heat. Although not a common phenomenon, evidence of this process can also be seen along the Smoky and Peace rivers as well as in the "Smoking Hills" of the Arctic coast.

The local bedrock is Cretaceous marine shale, which normally is impermeable, but slumping along the river banks continues to produce a number of fractures in the shale. Once exposed to air along these fractures, the iron-sulphide minerals, such as pyrite, quickly oxidize and create temperatures of over 300ºC. This heat bakes the nearby shale to a bright brick-red. Any groundwater that trickles down through fractures is quickly heated and turned into steam. Around the vents of escaping steam, native sulphur seeps through the fractured shale to solidify on the surface. Some of these sulphur seeps are currently burning and produce a very strong sour smell - a regular witch's brew!