The Ottawa-Gatineau region is underlain by three different geological materials that create very different landscapes. The resistant Precambrian granitic and metamorphic rocks of the Canadian Shield form highland areas that are characterized by rough terrain, numerous small lakes, and abundant rock outcrops (left). In contrast, the flat-lying Paleozoic rocks underlie lowland plains and low hills, and outcrops are confined largely to low scarps and riverbanks (bottom left). Much of the region is covered by a blanket of Quaternary sediments which form landscapes that range from gently undulating plains and low hills of glacial deposits to the flat plains of the Champlain Sea (bottom right).
Each geological material contains unique resources. Precambrian rocks contain a variety of metal and mineral resources. Paleozoic limestone and sandstone provide building stone and cement and concrete products. Quaternary sediments provide sand and gravel, and are also the parent material of agricultural soils.