Big Rock (also known as either
Okotoks Erratic or, by the Blackfoot Indians, as
Okotok) is a 16,500-tonne (18,200-ton)
boulder that is about the size of a two-story house and lies on the otherwise flat, relatively featureless, surface of the
Canadian Prairies in
Alberta. It is part of the
Foothills Erratics Train of typically angular boulders of distinctive
quartzite and pebbly quartzite.