Geology Volcanoes went rampant during the Ordovician, causing many igneous rocks to form out of ash and lava. The Ordovician was marked by periods of continental submergence. This climaxed by a Late Ordovician Flood that was the most widespread ever recorded. The predecessor of today's Atlantic Ocean began to shrink as the continents drifted closer together. Animal Life Because of these floods, Ordovician life was very dissimilar to Cambrian life. Particularly, brachiopods, trilobites, and mollusks underwent Jurassic evolution. Armored, jawless fish, the first vertebrates, appeared.   Plant Life Algae was abundant, and a lot of them formed reefs in the widespread ocean. It is unknown whether plants lived on land or not in this period. If they did, it would probably be in the form of moss and lichens.

A trilobite

A view of the Ordovician Seas

Paleozoic Era: Ordovician Period