Divisions of Geologic Time
Begin End Era Period Epoch Events
-10,000 years today Cenozoic Quaternary Holocene Recession of glaciers; extinction of megafauna; dominance of mankind
-2 My -10,000 years Pleistocene Glacial episodes, ice ages. More mammals develop, including the now extinct Saber-Toothed Tiger and the Mastadon. Modern man appears.
-5 My -2 My Tertiary Pliocene Monkeys, australopithecines
-24 My -5 My Miocene Rise of Colorado Plateau; formation of Basin and Range; beginning of mankind. Horses, dogs, bears, modern whales, S. American monkeys, modern birds. Ramapithecus appears.
-37 My -24 My Oligocene  Pigs, rhinoceros and tapirs
-58 My -37 My Eocene Rodents and primates evolve. Whales, horses appear
-65 My -58 My Paleocene Recovery from Cretaceous terminal event; ascendence of mammals; rise of Rockies: dinosaurs, pterosaurs, and ammonites extinct; rise of modern animals; shrubs, grasses, and other flowering plants... Mammals such as camels, bears, cats, monkeys, rodents, dogs. Grasses, and fruit develop similar to what we have today.
-140 My -65 My Mesozoic Cretaceous Dominance of dinosaurs; flowering plants; primates; evolution of birds; Rockies begin to rise; sea level stands at Fall Line; demise of dinosaurs and other large animals at end, probably resulting from Chicxulub impact (K-T terminal event): first angiosperm plants; Mesozoic reptiles peak of development, as well as the downfall of the great dinosaurs. Triceratops, Tyrannosaurus Rex, the giant Pterodactyl. 
-200 My -140 My Jurassic Beginning of birds: Pangea splits; Atlantic Ocean widens: Ferns, cycads, ginkgos, rushes, conifers, ammonites, lobster, shrimp, shellfish and other invertebrates; pterosaurs, archaeopteryx appears, giant dinosaurs develop, as well as abundant plant life. 
-250 My -200 My Triassic Pangea begins to split; Atlantic Ocean opens: invertebrates pervade; reptiles dominant: turtles, dinosaurs, ichthyosaurs. Beginning of dinosaurs, both plant and meat eaters, flying reptiles and crocodiles.
-290 My -250 My Paleozoic Permian Pangea intact; no Atlantic Ocean; demise of many marine animals; evolution of reptiles: Trilobites extinct; Amphibians and reptiles dominant land animals; gymnosperms dominant plants. Molluscs dominate the seas. At the end of the Paleozoic (The Permo-Triassic extinction event), the largest mass extinction in history wiped out approximately 90% of all marine animal species. Reptiles become abundant. Trees similar to pine develop.
-320 My -290 My Pennsylvanian Iapetus Ocean closes; Pangea coalesces; coal swamps; reptiles; the beds of the Cumberland Plateau are laid down
-360 My -320 My Mississippian Fern forests; sharks; the Highland Rim in TN and KY: foraminiferans, corals, bryozoans, brachiopods, blastoids; seed ferns are plentiful, lycopsids, and other plants; amphibians become more common.  The first reptiles evolve from the amphibians. Spiders, cockroaches, scorpions appear. First animals to live on dry land.
-410 M  -360 My Devonian Insects; amphibians: corals, brachiopods, ammonoids, crinoids and early land plants. Fish evolve into more complex animals, sharks and amphibians multiply. 
-440 My -410 My Silurian Vascular land plants, the first true plants appear; air-breathing animals: brachiopods,  corals; primitive fish... Crinoids are abundant, and eurypterids - believed to be the first air-breathing animal, appears.
-500 My -440 My Ordovician Fish; corals; the Nashville basin: graptolites dominant; also trilobites, brachiopods, bryozoans, gastropods, bivalves, echinoids, crinoids, cephalopods, and corals...Graptolites, Orthoceras, and primitive fish - the first verterbrates begin to appear.
-600 My -500 My Cambrian Proliferation of multi-cellular life: first marine animals with mineralized shells appear: trilobites, echinoderms, brachiopods, arthopods, molluscs, primitive graptolites; a variety of worms, algae, and many invertebraes similar to jellyfish and worms. The first shelled animals begin to appear.... 
-4500 My -600 My Pre-Cambrian Formation of Earth's crust; multiple tectonic cycles; oldest dated crustal rocks, -3900 My...beginnings of life; oldest evidence for life, -3800 My...Iapetus Ocean begins to open near one end.  During this time, the Earth formed, life arose, the first tectonic plates arose and began to move, eukaryotic cells evolved, first Oxygen/Ozone Layer Forms -2000 My -- and just before the end of the Precambrian, complex multicellular organisms, including the first animals, evolved. 



USGS booklet on geologic time

Geologic Time Scale Metaphor

Geological Time Machine

Toilet Paper Geologic Time Scale

Turtle Hill Sangha © 2010