How did the atmosphere change after the Precambrian?
Paleozoic climate changed as the earth evolved. The earth turned faster and the days were shorter. Tidal effects were stronger and there was no green covering of vegetation to better absorb the sun’s radiation. (See What Is Geologic Time?) The climate was cooler at the beginning of the Cambrian due to the ice age at the end of the Precambrian. Deposits of Early Ordovician age limestones indicate that there was a warming and the sea encroached on the land. Glacial deposits of Late Ordovician age have been found in the western part of the Sahara Dessert. These were extensive enough to bring about a decrease in the temperatures of the middle and high latitudes. During the Late Paleozoic, the South Pole was in South Africa; the North Pole was over open ocean. The equator trended northeastward across Canada and southwestward across Europe. Cooler climates prevailed in Gondwanaland because of its proximity to the South Pole. By the Permian, the southern continent was in an ice age. The north
