But once Gondwana took up its polar position in the late Ordovician, massive glaciers formed over Africa at the supercontinent's center. This heralded a 20-million-year ice age during which ...

This cooling event occurred during the late Ordovician period, around 445–443 million years ago, and is characterized by a significant global glaciation that led to widespread ice sheets ...

The Ordovician period and its impact spike correspond closely with a period of intense cold for our planet known as the Hirnantian glaciation—or, more dramatically, as the Hirnantian Icehouse.