The Geologic Time ScaleThe Geologic Time Scale

Sections of timeSections of time

• ERATwo or more geological periods comprise an era, which is hundreds of millions of years in duration.

• PERIODThe period is the basic unit of geological time in which a single type of rock system is formed, lasting tens of millions of years.EPOCHAn epoch is a division of a geologic period; it is the smallest division of geologic time, lasting several million years.

• Eon- Era- Period- Epoch- Age.

• Humans as we know ourselves appeared in the Pleistocene Epoch of the Quaternary Period in the Cenozoic era of the Phanerozoic Eon…..

Pre Cambrian timePre Cambrian time

• 4.6 Billion years ago- 542 MA

• Earth Forms• Stromatolites are

dominant life form

Paleozoic EraPaleozoic Era

• 542 to 251 mya • Multicellular life!!

Paleozoic, Cambrian, Paleozoic, Cambrian,

• 488-542 MA• Trilobites dominate• many phyla develop.• “Cambrian Explosion”

Paleozoic, Ordovician, Paleozoic, Ordovician,

• 488 to 444 mya • North America is

under shallow sea.• Modern Oxygen rich

atmosphere develops• Vertebrates Develop

Paleozoic, SilurianPaleozoic, Silurian

• 444 MA 416 MA• First Land Plants and

Animals

Paleozoic, Devonian, Paleozoic, Devonian,

• 416 MA -359 MA• First amphibians• Age of fishes

Paleozoic, Carboniferius, Paleozoic, Carboniferius, MissippianMissippian

• 359 MA – 318 MA• Amphibians Flourish• Forests and swamps

cover land

Paleozoic, Carboniferius, Paleozoic, Carboniferius, PennsylvanianPennsylvanian

• 318 MA – 299 MA• Giant flying insects• First Reptiles, ROAR!!

Paleozoic, PermianPaleozoic, Permian

• 299 MA – 251 MA• Pangea comes

together

Mesozoic EraMesozoic Era

• "The Age of Reptiles"

251 MA to 65.5 MA

Mesozoic, TriassicMesozoic, Triassic

• 251 MA – 200 MA• Dinosaurs appear• Mammals appear

• Cycads and conifers dominate

Mesozoic, JurassicMesozoic, Jurassic

• 200 MA- 146 MA• Dinosaurs are the

dominant animal.• Primitive vertebrate

flight, first birds

Mesozoic, Cretaceous, Mesozoic, Cretaceous,

• 146-65.5MA• Flowering plants

appear (angiosperms)• Modern Birds• All good until……

K-T ExtinctionK-T Extinction

• 65MA• Kills off Dinosaurs• Asteroid or volcano• Iridium rich dust….

Cenozoic EraCenozoic Era

"The Age of Mammals"

65.5 mya through today

Continents at present locations

Cenozoic, Tertiary, PaleoceneCenozoic, Tertiary, Paleocene

Tertiary-

65-55.8 mya

Paleocene- age on mammals begins

First Primates

Cenozoic, Tertiary, EoceneCenozoic, Tertiary, Eocene

• 55.8-33.9 mya • Rodents appear.

Primitive whales appear.

Cenozoic, Tertiary,OligoceneCenozoic, Tertiary,Oligocene

• 33.9-23 mya • Dogs and cats

appear!• But they did not look

like that -

Cenozoic, Tertiary, MioceneCenozoic, Tertiary, Miocene

• 23-5.3 MA• Due to high

abundance of grasses, herds of large mammals abound.

Cenozoic, Tertiary, PlioceneCenozoic, Tertiary, Pliocene

• 5.3-1.8• First hominids

(australopithecines). Modern forms of whales. Megalodon swam the seas

• Hominid- where humans and apes split

• Lions Tigers and Bears….

• Appear in the Pliocene

Cenozoic, Quauernary, PleistoceneCenozoic, Quauernary, Pleistocene

• Quaternary Period"The Age of Man"1.8 mya to today

• Pleistocene- The Last Ice Age1.8-.012 ma

• Humans (Homo sapien) appear. You better remember this!

• Mammoths, saber-toothed cats,

Quaternary, HoloceneQuaternary, Holocene

• 11,500 ya to today • Marked by complex

human civilization• Ice melted, and sea

level rose 140 m!