Big Rock (also known as either Okotoks Erratic or, in

Blackfoot The Blackfoot Confederacy, ''Niitsitapi'' or ''Siksikaitsitapi'' (ᖹᐟᒧᐧᒣᑯ, meaning "the people" or "Blackfoot language, Blackfoot-speaking real people"), is a historic collective name for linguistically related groups that make up t ...

, as Okotok) is a 16,500-tonne (18,200-ton)

boulder In geology, a boulder (or rarely bowlder) is a rock fragment with size greater than in diameter. Smaller pieces are called cobbles and pebbles. While a boulder may be small enough to move or roll manually, others are extremely massive. In ...

that lies on the otherwise flat, relatively featureless, surface of the

Canadian Prairies The Canadian Prairies (usually referred to as simply the Prairies in Canada) is a region in Western Canada. It includes the Canadian portion of the Great Plains and the Prairie Provinces, namely Alberta, Saskatchewan, and Manitoba. These provin ...

Alberta Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest T ...

. It is part of the Foothills Erratics Train of typically angular boulders of distinctive

quartzite Quartzite is a hard, non- foliated metamorphic rock which was originally pure quartz sandstone.Essentials of Geology, 3rd Edition, Stephen Marshak, p 182 Sandstone is converted into quartzite through heating and pressure usually related to tec ...

and pebbly quartzite. This massive angular boulder, which is broken into two main pieces, measures about and is high. It consists of thick-bedded,

mica Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into extremely thin elastic plates. This characteristic is described as perfect basal cleavage. Mica is ...

ceous, feldspathic quartzite that is light grey, pink, to purplish. Besides having been extensively fractured by frost action, it is unweathered. Big Rock lies about west of the town of

Okotoks Okotoks (, originally ) is a town in the Calgary Region of Alberta, Canada. It is on the Sheep River, approximately south of Calgary. Okotoks has emerged as a bedroom community of Calgary. According to the 2016 Census, the town has a population ...

, Canada, south of Calgary in the SE. 1/4 of Sec. 21, Township 20, Range 1, West 5th Meridian.Stalker, A MacS (1975). "The big rock." In Structural geology of the foothills between Savanna Creek and Panther River, S.W. Alberta, Canada. May 23, 1975. H. J. Evers and J. E. Thorpe, eds., pp. 9-11. Calgary, Alberta, Canada: Canadian Society of Petroleum Geologists.Cruden, DM, W Langenberg, and RC Paulen (2003). ''Geology of the Frank Slide and southwestern Alberta. Edmonton Geological Society – Geological Association of Canada annual field trip celebrating the 100th anniversary of the Frank Slide Disaster.'' Edmonton, Alberta: Edmonton Geological Society. 34 pp. Big Rock is a

glacial erratic A glacial erratic is glacially deposited rock differing from the type of rock native to the area in which it rests. Erratics, which take their name from the Latin word ' ("to wander"), are carried by glacial ice, often over distances of hundred ...

that is part of a long, narrow ( wide), linear scatter of thousands of distinctive

and pebbly quartzite glacial erratics between and in length. This linear scatter of distinctive quartzite glacial erratics is known as the Foothills Erratics Train. The Foothills Erratics Train extends along the eastern flanks of the

Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico ...

of Alberta and northern

Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columb ...

to the International Border. The boulders and smaller gravel, which comprises the Foothills Erratics Train, consist of Lower

Cambrian The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ago ...

shallow marine quartzite and conglomeratic quartzite, which occurs only within the Gog Group and is found in the

Athabasca River The Athabasca River (French: ''Rivière Athabasca'') is a river in Alberta, Canada, which originates at the Columbia Icefield in Jasper National Park and flows more than before emptying into Lake Athabasca. Much of the land along its banks is ...

Valley of central western Alberta. Big Rock is the largest erratic within the Foothills Erratics Train. Lying on prairie to the east of the Rocky Mountains and like all the larger erratics. it is visible for a considerable distance across the prairie and, likely served as a prominent landmark for Indigenous people.Stalker, A MacS (1956). "The erratics train, Foothills of Alberta." Geological Survey of Canada, Bulletin no. 37, 28 p.

Geologic history

Near the end of the

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...

Period, between 12,000 and 17,000 years ago, a massive landslide occurred within the upper reaches of the Athabasca River valley. As a result of this landslide, millions of tonnes of beige to pinkish quartzite and quartzitic conglomerate slid from the side of a mountain and onto the top of a valley glacier within the Athabasca River valley. On its top, the narrow valley glacier carried eastward this mass of Gog Group quartzite and quartzitic conglomerate. Because it lay on and within the top of this glacier, the highly fractured boulders were neither broken up into smaller blocks nor rounded by movement of the glaciers that transported it. After leaving the Rocky Mountains, the valley glacier collided with the westward moving ice streams of the Laurentide Ice Sheet and both it, other Rocky Mountain valley glaciers, and Laurentide ice streams coalesced as ice streams and were diverted southward and parallel to the eastern flanks of the Rocky Mountains. Together they flowed as far south as northern Montana as an ice sheet before they stagnated and melted. When the ice sheet melted, erratics of Gog quartzite and quartzitic conglomerate were dropped to form the line of rocks known as the Foothills Erratics Train. Big Rock is one of these glacial erratics of Gog quartzite and quartzitic conglomerate that originated as part of a landslide in the Athabasca River valley and carried on the top of a glacier, later ice stream, to its present site.

History

The people of the

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"'' , meaning "rock" in the

Blackfoot language The Blackfoot language, also called Siksiká (its denomination in ISO 639-3, ; Siksiká ik͡siká syllabics ), often anglicised as ', is an Algonquian language spoken by the Blackfoot or ''Niitsitapi'' people, who currently live in the nor ...

, and may refer to the rock.Town of Okotoks - Okotoks' Beginnings
Retrieved 2012-02-09 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. James Hector, a geologist with the Palliser Expedition, first documented the rock in 1863. He misidentified the feature as a

klippe 350px, Schematic overview of a thrust system. The shaded material is called a window_(geology).html"_;"title="nappe._The_erosional_hole_is_called_a__window_(geology)">window_or_fenster._The_klippe_is_the_isolated_block_of_the_nappe_overlying_aut ...

Indigenous perspective

One interesting feature of Big Rock is the large split down the middle. A Blackfoot story describes how this may have happened: One hot summer day, Napi, the supernatural trickster of the Blackfoot peoples, rested on the rock because the day was warm and he was tired. He spread his robe on the rock, telling the rock to keep the robe in return for letting Napi rest there. Suddenly, the weather changed and Napi became cold as the wind whistled and the rain fell. Napi asked the rock to return his robe, but the rock refused. Napi got mad and just took the clothing. As he strolled away, he heard a loud noise and turning, he saw the rock was rolling after him. Napi ran for his life. The deer, the bison and the pronghorn were Napi's friends, and they tried to stop the rock by running in front of it. The rock rolled over them. Napi's last chance was to call on the bats for help. Fortunately, they did better than their hoofed neighbours, and by diving at the rock and colliding with it, one of them finally hit the rock just right and it broke into two pieces. Not only does this story explain why the rock is in two pieces, but also why bats have squashed-looking faces. The tale provides helpful caution against taking back what you have given away. Retrieved 2016-02-11

Present day

Although it has been claimed to be the largest glacial erratic in the world, e.g. Sterenberg (2013),Sterenberg, G., 2013. ''Learning Indigenous and Western mathematics from place.'' ''Mathematics Education Research Journal'', 25(1), pp.91-108. Big Rock is not. For example, one large glacial erratic in Germany measures and is thick.Shroder, J. F. (2011). ''Landforms of Glacial Transportation.'' In ''Encyclopedia of Snow, Ice and Glaciers, Encyclopedia of Earth Sciences Series.'' V. P. Singh, P. Singh, and U. K. Haritashya, eds., pp. 693-694. Springer, AA Dordrecht, The Netherlands, 1254 pages Near Cooking Lake, Alberta, one of several large glacial erratics, which is called the ''Cooking Lake (Number 6) megablock'', covers an area of at least , has a length of and is about thick. Pollen studies indicate that the Lower

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

sedimentary strata that comprise this glacial erratic were transported a minimum distance of about .Stalker, A MacS (1976). "Megablocks, or the enormous erratics of the Albertan prairies." Paper no. 76-1C, pp. 185-188. Ottawa, Ontario: Geological Survey of Canada. Big Rock is located along the side of Highway 7, and public parking is available at the turn-off. Despite the presence of a fence around Big Rock and a sign telling people not to climb, many tourists, who visit the rock, ignore the warnings to either

or climb the tall erratic.Brink, J.W., 2014. ''Managing Chaos: Vandalism and Rock-Art at the Okotoks Erratic, Alberta, Canada.'' In ''Open-Air Rock-Art Conservation and Management: State of the Art and Future Perspectives'', edited by Timothy Darvill and António Pedro Batarda Fernandes, pp. 174–188. Routledge, New York.

In popular culture

Big Rock Brewery in Calgary is named after Big Rock.Patterson, M., and N. Hoalst-Pullen (2014) "The Geography of Beer: Regions, Environment, and Societies." New York, New York: Springer Dordrecht.

References

External links

*Brink, J. (2014
''Okotoks Big Rock – Managing Vandalism with Technology''
Aboriginal Heritage Section, Alberta's history
Retroactive
Alberta Government (June 17, 2014). {{DEFAULTSORT:Big Rock (Glacial Erratic) Landforms of Alberta Glacial erratics of Canada Foothills County Okotoks Provincial historic sites of Alberta Provincial Historic Resources of Alberta Quartzite formations Individual rocks