Geologic TimeGeologic Time

A brief history of our A brief history of our planet…planet…

How were these divisions created?How were these divisions created?

fossil recordfossil record

Other geologic eventsOther geologic events

EonEon

Largest, most general Largest, most general division of timedivision of time

4 Eons4 Eons Hadean, Archean, Hadean, Archean,

Proterozoic combined Proterozoic combined are Precambrian Timeare Precambrian Time

PhanerozoicPhanerozoic

EraEra Each Eon is broken up into ErasEach Eon is broken up into Eras 3 major eras in Earth’s history3 major eras in Earth’s history

Precambrian Time* 4.5 bya-Precambrian Time* 4.5 bya-540 mya540 mya

Paleozoic 540mya- 250myaPaleozoic 540mya- 250myaMesozoic 250 mya- 65 myaMesozoic 250 mya- 65 myaCenozoic 65 mya-presentCenozoic 65 mya-present

*Precambrian Time NOT an era, *Precambrian Time NOT an era, rather several eras combinedrather several eras combined

PeriodsPeriods

Each Era is divided Each Era is divided into even more into even more specific blocks of specific blocks of time called periodstime called periods

characteristic characteristic organisms organisms

geologic events geologic events associated with itassociated with it

Precambrian timePrecambrian time

4 billion years (4.5bya-540mya)4 billion years (4.5bya-540mya) volcanism creating Earth’s crustvolcanism creating Earth’s crust simple organisms- bacteria, algae, simple organisms- bacteria, algae,

protozoaprotozoa Oldest rocks = 3.5 billion years old- Oldest rocks = 3.5 billion years old-

So how do we know that Earth is 4.6 So how do we know that Earth is 4.6 billion years old?billion years old?

Paleozoic EraPaleozoic Era

540-250 mya540-250 mya ““Cambrian Cambrian

Explosion”Explosion”

Middle of Middle of Paleozoic- Paleozoic- transitiontransition

End Permian Mass End Permian Mass ExtinctionExtinction

Mesozoic EraMesozoic Era

250-65 mya250-65 mya ““Age of Dinosaurs”Age of Dinosaurs”

Lizards/reptiles are Lizards/reptiles are dominantdominant

Birds and mammals Birds and mammals also appearedalso appeared

Cenozoic EraCenozoic Era

65 mya-today65 mya-today mammals and birds mammals and birds

flourishflourish Age of MammalsAge of Mammals Mammals became Mammals became

largerlarger Global temperatures Global temperatures

cooledcooled Apes and humans Apes and humans

appearedappeared

Mass ExtinctionsMass Extinctions 5 major mass extinctions 5 major mass extinctions

1.1.EndEnd OrdovicianOrdovician

2.2.DevonianDevonian

3.3.EndEnd Permian (aka Permo-Triassic)Permian (aka Permo-Triassic)

4.4.EndEnd TriassicTriassic

5.5.Cretaceous (K/T)Cretaceous (K/T)