Geologic Time Scales

Geologic Time
Paleozoic Era
Cambrian Period
Ordovician Period
Silurian Period
Devonian Period
Carboniferous Period
Mesozoic Era
Triassic Period
Jurassic Period
Cretaceous Period
Cenozoic Era
Tertiary Period
Quaternary Period
Geologic Timeline

Web Sites

Paleozoic Era. UC Berkeley

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Geologic Time Scales

Ordovician Period

Dating from 505-440mya, the Ordovician Period saw one land mass, Gondwana, with nothing but a vast ocean lying to the north. Plants began a colonization of the land.The Ordovician Period saw the first arthropods appear on Earth. The first mass extinction marked the end of the Ordovician, when an ice age began about 440mya.