During the Ordovician, a few animals and plants began to explore the margins of the land, but nothing colonised beyond these beachheads, so the majority of life was still confined to the seas. The Ordovician began with shallow, warm seas but the end of the period experienced a 500,000 year long ice age, triggered by the drift of the supercontinent, Gondwana, to the south polar regions. The Ordovician ended with a mass extinction.
Began: 495 million years ago
Ordovician-Silurian mass extinction
443 million years ago
Reconstruction of the Earth in the Ordovician period, 495 million - 443 million years ago. Credit: Dr Ron Blakey, NAU Geology.