... istribution. This illustration shows the extent of the ice during a time when the glaciation was dominated by changes in the eccentricity - or elongation - of the Earth's orbit around the Sun. Ice coverage was relatively extensive during this period, ...

Artwork showing a map of the south polar regions of Earth during the late Ordovician Period (480 MYa). Scientists have identified two distinctive cyclic episodes of glaciation, each due to a different cause and having different effects on ice distrib...