Topographically, Anticosti Island can be divided into three distinct regions: two lowland areas, rarely exceeding in elevation, in the eastern and western thirds of the island linked along the coast; and a central highland forming a plateau that rises to just over . This plateau is an unidirectional structure slightly tilted to the south, and is characterized by rolling cuestas. The rocks exposed on the island form a continuous sedimentary stratum more than thick. These are the most complete strata in eastern North America of the Ordovician and Silurian periods.