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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!