The drift plains can be described as gently rolling till plains which are underlain by glacial drift. They include ground moraines and are characterized by low-relief terrain consisting of gently undulating hills and valleys. These drift plains are mostly covered with a thick layer of glacial till, which is a mixture of clay, silt, sand, and gravel deposited by glaciers. The topography of the drift plains is often determined by the underlying bedrock, which may consist of sedimentary rocks, igneous rocks, or metamorphic rocks. The drift plains are typically found in areas that were glaciated during the last ice age, such as the northern United States, Canada, and northern Europe.