The strata were laid down in several cycles of glaciations and warmer interglacial interludes. Scotland was entirely covered in ice during the Pleistocene glaciations. The Pleistocene covers the recent period of repeated glaciations. The Pleistocene glaciations entirely covered the islands. The repeated glaciations of the Pleistocene were caused by the same factors. In the Middle Pleistocene, there were two powerful glaciations. The upper boundary was set at the start of the Pleistocene glaciations. The plateau is underlain by Pierre shale covered with hardened deposits from repeated glaciations. Icehouse is characterized by frequent continental glaciations and severe desert environments. Evidence indicates that the Pikes Peak unconformity was formed before the Snowball Earth glaciations. CO models suggest that values were low in the late Cenozoic and Carboniferous-Permian glaciations. The Cenozoic glaciations that affected Fennoscandia most likely began in the Scandinavian Mountains. Most river systems in Ireland formed in the Cenozoic before the Quaternary glaciations. There is evidence that the first known glaciations occurred during the Proterozoic. The area was affected by sea level changes during the repeated Quaternary glaciations.