The document summarizes Earth's geologic history from its formation 4.6 billion years ago to the present. It is divided into eons, eras, periods, and epochs. The earliest eons included the Hadean and Archean, when Earth was molten and the first life formed. The Proterozoic saw continued formation of continents and oxygen buildup. The Phanerozoic eon saw the rise of complex life, including during the Paleozoic era of the Cambrian, Ordovician, and other periods. During the Mesozoic era, life included dinosaurs and the breakup of Pangaea. The Cenozoic era is the current one including the C

1. Earth’s HistoryGeologic Time ScaleZach WatersPh Sc 107Summer 2011

2. The Earth is 4.6 billion years oldThe Earth’s history can be divided into major units of time-Eon-Era-Period-Epoch

3. How it all startedPrecambrian Super Eon: “time before life”Hadean Eon* 4.6 – 3.8 billion years ago (BYA)Heavy bombardment of meteorites Earth’s surface molten lava*Note: Not considered a part of the geological time scale (no evidence)

4. Precambrian Super EonArchean Eon: 3.8 – 2.5 BYAEarth starts cooling from molten stateCrust forms – Continental building Surface temperatures still really hot Oceans emerge Reducing atmosphere of methane, ammonia, hydrogen, and other gases. Earliest bacteria forms

5. Precambrian Super EonProterozoic Eon: 2.5 BYA – 542 million years ago (MYA)Continued accretion of continental landmassesBuild up of oxygen thanks to bacteria algae etc…Many glaciations occurred (Snowball Earth)Evidence of earliest marine life Rodinia

6. Phanerozoic Super Eon542 MYA - Present “Beginning of life”Paleozoic Era: 542 MYA– 251 MYA Cambrian Period 542 MYA – 488 MYA Ordovician Period 488 MYA – 443 MYASilurian Period 443 MYA – 416 MYA Devonian Period 416 MYA – 359 MYACarboniferous Period 359 MYA – 299 MYA Permian Period 299 MYA – 251 MYA

7. Cambrian Period542 MYA – 488 MYAClimate: Moderately warm, not entirely without glaciations Flora: No land plants, abundant fungi, algae Fauna: Explosion of marine invertebratesContinental Masses: trilobite fossil

8. Ordovician Period488 MYA – 443 MYAClimate: Moderately warm, not entirely without glaciations Flora: Evidence of primitive land plantsFauna: Marine invertebrates, some early vertebrates jawless fishContinental Masses:Super-Continent GondwanaIce-age at end of periodMass extinction of organisms

9. Silurian Period443 MYA – 416 MYAClimate: Moderately warmer, stable temps. Less glaciationsFlora: Primitive plants found on landFauna: Marine invertebrates, vertebrates fish with jawsContinental Masses:Super-Continent GondwanaCouple minor mass extinction of organisms due to rapidchanges in sea level

10. Devonian Period416 MYA – 359 MYAClimate: Relatively warmer, stable temps. Lacked glaciersFlora: Widespread shrubs & treesFauna: Widespread marine life “The Age of Fish” sharks, fish crawling out of water, early evidence amphibiansContinental Masses:Super-Continent GondwanaContinent SiberiaContinent EuramericaPanthalassa (universal ocean)Some extinction of marine lifeGlacial conditions start

11. Carboniferous Period359 MYA – 299 MYA: Two sub-periodsMississippian Period 359 – 318 MYAPennsylvanian Period 318 – 299 MYAClimate: Mostly warm early, later cooled to glaciations in southern GondwanaFlora: Widespread shrubs & small trees, rainforestFauna: Amphibians, many fish & marine, insectsContinental Masses:Rainforest CollapsePeriod ending Ice-ageAppalachian Mountains form

12. Permian Period299 MYA – 251 MYAClimate: Varied, cycled between warm & cool cyclesFlora: Diverse plantsFauna: Reptiles, fully terrestrial, more insectsContinental Masses:Pangaea formsEra ended with mass extinction

13. Phanerozoic Super Eon542 MYA - PresentMesozoic Era: 251 MYA– 65 MYA “Middle Life”Triassic Period 251 MYA – 199 MYA Jurassic Period 199 MYA – 145 MYACretaceous Period 145 MYA – 65 MYA

14. Triassic Period251 MYA – 199 MYAClimate: Hot and dry, Seasonal hot summers/cold winters, no evidence of glaciationsFlora: Full recovery of woody treesFauna: First dinosaurs, first flying vertebrates, first mammals, new corals/reefsContinental Masses:Pangaea rifting Period ended with mass extinction severe inoceans

15. Jurassic Period199 MYA – 145 MYAClimate: Warm, humidFlora: Large forests and junglesFauna: Larger dinosaurs Continental Masses:Pangaea breaks apart into northern (Laurasia) &southern (Gondwana) supercontinentsRocky Mts. starting to uplift

16. Cretaceous Period145 MYA – 65 MYAClimate: WarmFlora: Flowering plants spread, many leafy treesFauna: Dinosaurs, reptiles, mammals, birds, marineContinental Masses:Pangaea completely breaks up into today's continentsHigh sea levelsEnded with largest mass extinctions in Earth historyDemise of land dinosaurs, much other fauna & flora

17. Phanerozoic Super Eon542 MYA - PresentCenozoic Era: 65 MYA– Present “Age of mammals”Paleogene Period 65 MYA – 23 MYA Neogene Period 23 MYA – 2.6 MYAQuaternary Period 2.6 MYA – Present

18. Paleogene Period65 MYA – 23 MYA Paleocene Epoch 65 MYA – 56 MYAEocene Epoch 56 MYA – 34 MYA Oligocene Epoch 34 MYA – 23 MYA

19. Paleogene PeriodPaleocene Epoch: 65 MYA – 56 MYAClimate: Cooler & dryer, became warm & humidFlora: Ferns, tropical forest, rain forestFauna: Small mammals, reptiles, amphibians, birds, insectsContinental Masses:Continents continue to driftHimalayas begin formingWarm oceans

20. Paleogene PeriodEocene Epoch: 56 MYA – 34 MYAClimate: Global temps. high, tropical climatesFlora: Covered in large forests apart from desertsFauna: First modern mammalsContinental Masses:Continents continue to driftHimalayas formWarm oceans

21. Paleogene PeriodOligocene Epoch: 34 MYA – 23 MYAClimate: Global cooling, increase in ice volumeFlora: Expansion of grasslands, regression in tropicalFauna: Larger mammals, modern marine animalsContinental Masses:Continents continue to driftAlps risingSea levels decreaseOceans coolingFirst Antarctic permanent ice-sheets

22. Neogene Period23 MYA – 2.6 MYA Miocene Epoch 23 MYA – 5.3 MYAPliocene Epoch 5.3 MYA – 2.6 MYA

23. Neogene PeriodMiocene Epoch: 23 MYA – 5.3 MYAClimate: Global coolingFlora: Fairly modernFauna: Land and marine fairly modernContinental Masses:Continents continue to driftHimalayas risingAndes risingMtn. building widespread

24. Neogene PeriodPliocene Epoch: 5.3 MYA – 2.6 MYAClimate: Seasonal cooler & drier average temperatureFlora: Tropical forest limited to equator, grasslands spread Fauna: Modern marine, animals, and mammalsContinental Masses:Continents continue to driftEnd of period glaciations began into the Ice-age

25. Quaternary Period2.6 MYA – Recent Pleistocene Epoch 2.6 MYA – .0117 MYAHolocene Epoch .0117 MYA – Recent

26. Quaternary PeriodPleistocene Epoch: 2.6 MYA – .0117 MYAClimate: Moderately cooler/coldFlora: ModernFauna: Essentially modernContinental Masses:Ice-Age – 30% Earth’s surfaceEvidence of early HumansExtinction of large mammals

27. Quaternary PeriodHolocene Epoch: .0117 MYA – RecentClimate: End of Ice-Age, warm, modern temperaturesFlora: Modern, not evolved muchFauna: Modern, not evolved muchContinental Masses:Human species world-wideHuman developmentLarge animals disappeared