Hoodoos take millions of years to form and stand 5 to 7 metres tall. Each hoodoo is a sandstone pillar resting on a thick base of shale that is capped by a large stone. Hoodoos are very fragile and can erode completely if their capstone is dislodged (in other words, no climbing allowed). The name "Hoodoo" comes from the word "voodoo" and was given to these geological formations by the Europeans. In the Blackfoot and Cree traditions, however, the Hoodoos are believed to be petrified giants who come alive at night to hurl rocks at intruders.