Big Rock (glacial erratic)
Big Rock (also known as Okotoks Erratic) is a glacial erratic situated 7 km (4.3 mi) west of the town of Okotoks, Alberta, Canada (18 km (11 mi) south of Calgary). The 16,500-tonne (18,200-ton) quartzite boulder is the world's largest known glacial erratic.
Big Rock is one of several thousand erratics found in Alberta and Montana called the Foothills Erratics Train, which originated from a landslide in the Tonquin Valley of Jasper National Park, from Lower Cambrian-aged Gog Group. Big Rock was transported along the confluence of the Cordilleran Ice Sheet and the Laurentide Ice Sheet approximately 12 to 18 thousand years ago  to its present location.
The people of the Blackfoot First Nation used Big Rock as a landmark for finding a crossing over the Sheep River (where Okotoks stands today) long before European settlement. The town's name, Okotoks, is derived from "o'kotok" [ˈokətok], meaning "rock" in the Blackfoot language, and may refer to the rock. The rock also contains native pictographs and was considered a medicine rock to the natives. In the 1970s the government declared it a Provincial Historic Site to protect its geological and cultural importance.
The erratic is clearly visible from the side of Highway 7, and public parking is available at the turn-off. While there is a fence around the Big Rock and a sign telling people not to climb, many people visit the rock and ignore the warnings to either boulder or climb the 9-metre (30 ft) tall erratic.
In popular culture
Big Rock Brewery in Calgary is named after Big Rock.
- "Okotoks Erratic". Government of Alberta.
- Lionel E. Jackson, Jr., Elizabeth R. Leboe, Edward C. Little, Philip J. Holme, Stephen R. Hicock, and Kazuharu Shimamura (1999). "CANQUA 99 Guidebook: Late Quaternary Geology of the Foothills, from Calgary to the Alberta–Montana Border" (PDF).
- Jackson, Lionel E.; Fred M. Phillips; Edward C. Little (1999). "Cosmogenic 36Cl dating of the maximum limit of the Laurentide Ice Sheet in southwestern Alberta". Canadian Journal of Earth Sciences 36 (8): 1347–1356. doi:10.1139/cjes-36-8-1347.
- Jackson, Lionel E.; Elizabeth R. Leboe; Edward C.Little; Phillip J. Holme; Stephen R. Hicock; Kazuharu Shimamura; Faye E. Nelson (2008). "Quaternary stratigraphy and geology of the Rocky Mountain Foothills, southwestern Alberta". Geological Survey of Canada Bulletin 583. doi:10.4095/224301.
- Town of Okotoks - Okotoks' Beginnings Retrieved 2012-02-09