Rat’s Nest Cave: a guided adventure
Rat’s Nest Cave is one of Canada’s most accessible caves, offering over four kilometres of explored passages reaching a depth of 245 metres. It is not Canada’s longest or deepest cave, but it is accessible year round. The cave’s entrance sits 180 metres above the valley floor on Grotto Mountain, just east of Canmore.
Its international reputation is generated by the rich display of geologic features and formations encountered by those willing to go down and get dirty. The cave was designated a Provincial Historic Site in 1987 in an effort to promote wise stewardship of this local resource.
The story of the Rat’s Nest Cave is as old as the Grotto Mountain rock it is eroded from. Limestone, mudstones, and siltstones tell of an equatorial coral sea 340 million years ago. About 85 million years ago, the westward drift of the North American continent caused the sedimentary layers to fold, fault, and thrust upward in a spectacular uplift that formed the front ranges of the Rocky Mountains, including Grotto Mountain. The uplifting associated with the formation of the frontal ranges created fractures in the sedimentary rock layers, and water inevitably infiltrated and exploited even the smallest voids in the rock. Initially, the passages were not tunnels that would allow human passage. Beginning about 1.6 million years ago and ending 13,000 years ago, the continent underwent several massive glaciations. Towards the end of each glacial advance, warming unleashed tremendous volumes of glacial meltwater enlarging the fractures in the rock layers and carving them into an extensive system of wells, tunnels, and chambers.
In 1858, James Hector and Eugene Bourgeau, of the Palliser Expedition, made an obscure reference to a cave they found on or near Grotto Mountain. It may have been Rat’s Nest Cave. The first serious caving began about 1965. More recently, the passageways have been mapped, formations photographed, and several sediment-filled passages excavated; the work continues currently. Today, professional guides escort more than 1,000 hardy adventurers each year through the designated portions of the labyrinth.
The cave’s entrance, a breach in the subterranean passages caused by glacial erosion, is located on land controlled by Graymont, a lime production facility located just east of Exshaw. Graymont has legal guardianship of the area and is rightly concerned with trespassing near its active quarry.
The company has erected a substantial metal gate that is designed to allow bats and packrats unobstructed access, but to control human access to the cave by lock and key. In conjunction with Alberta Community Development Ministry (now Alberta, Tourism, Parks, and Recreation Ministry) and under an agreement with Canmore Caverns Ltd., Graymont continues to participate in a program that allows access to the caves. The goal is to maximize safety, protect the fragile resource from damage, allow high quality caving experiences, and promote further scientific investigation. Currently, an exhibit on the cave can be viewed at the Canmore Museum and Geoscience Centre. To arrange for a guided tour of Rat’s Nest Cave contact Charles “Chas” Yonge, Ph.D., owner of Canmore Caverns Ltd. Phone 877-317-1178 (toll free).
By Dene Cooper