geologic time, geological time - the time of the physical formation and development of the earth (especially prior to human history)

Age of Man, Quaternary, Quaternary period - last 2 million years

Tertiary, Tertiary period - from 63 million to 2 million years ago

Cretaceous, Cretaceous period - from 135 million to 63 million years ago; end of the age of reptiles; appearance of modern insects and flowering plants

Jurassic, Jurassic period - from 190 million to 135 million years ago; dinosaurs; conifers

Triassic, Triassic period - from 230 million to 190 million years ago; dinosaurs, marine reptiles; volcanic activity

Permian, Permian period - from 280 million to 230 million years ago; reptiles

Carboniferous, Carboniferous period - from 345 million to 280 million years ago

Pennsylvanian, Pennsylvanian period, Upper Carboniferous, Upper Carboniferous period - from 310 million to 280 million years ago; warm climate; swampy land

Lower Carboniferous, Lower Carboniferous period, Missippian period, Mississippian - from 345 million to 310 million years ago; increase of land areas; primitive ammonites; winged insects

Age of Fishes, Devonian, Devonian period - from 405 million to 345 million years ago; dominance of fishes and appearance of amphibians and ammonites

Silurian, Silurian period - from 425 million to 405 million years ago; first air-breathing animals

Ordovician, Ordovician period - from 500 million to 425 million years ago; conodonts and ostracods and algae and seaweeds

Cambrian, Cambrian period - from 544 million to about 500 million years ago; marine invertebrates

geological era, era - a major division of geological time; an era is usually divided into two or more periods

epoch - a unit of geological time

glacial epoch, glacial period, ice age - any period of time during which glaciers covered a large part of the earth's surface; "the most recent ice age was during the Pleistocene"