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Earth’s Past

Earth’s Past. The Geologic Time Scale. Earth’s history is divided different sections of time The sections are determined by the living things and the rock record The geologic time scale is broken up into eons , eras , periods , and sometimes epochs. Epochs – Divide periods

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Earth’s Past

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  1. Earth’s Past

  2. The Geologic Time Scale Earth’s history is divided different sections of time The sections are determined by the living things and the rock record The geologic time scale is broken up into eons, eras, periods, and sometimes epochs

  3. Epochs – Divide periods Periods – Divide eras Eras – Divide eons Eons – Longest segment of geologic time

  4. Changes Earth has changed dramatically over time Earth atmosphere initially comprised of CO2, Sulfur Dioxide, Water Vapor, and Nitrogen Liquid Oceans Developed Oxygen (O2) entered the atmosphere with the appearance of photosynthetic organisms, such as algae Living things have evolved and mass extinctions have occurred

  5. Evolution Since appearing on Earth, animals and plants have been changing in appearance, size, and structure This change is called evolution. In the 1800’s, Charles Darwin called the process of the species that survive due to traits better suited to the environment natural selection

  6. The Precambrian (4.5-543 mya) Precambrian time includes all geologic time before the Cambrian period in the Paleozoic era. This is the combination of the Hadean Archean Proterozoic

  7. The PrecambrianHadean●Archean●Proterozoic • Hadean Eon • The Formation of Earth • Meteor Impacts • No Life • Volcanic Activity • Formation of Early Atmosphere • Cooling of Water Vapor to Form Oceans

  8. The PrecambrianHadean●Archean●Proterozoic • Archean Eon • (3.8-2.5 bya) • Started with the formation of the crust and first rocks (3.8 bya) • The Cratons are the oldest Archean

  9. The PrecambrianHadean●Archean●Proterozoic • The first evidence of life is found in Archean rocks • Simple bacteria (3.8 bya) • Cyanobacteria – simple single celled organisms (3.5 bya) • Trapped in sediment they form structures called stromalolites • Photosynthesis began ~3 bya

  10. The PrecambrianHadean●Archean●Proterozoic Proterozoic Eon • (2.5 bya -543 mya) • Abundant volcanic activity • No life on land • All organisms had soft bodies • Multicellular life began(2.1 bya) • Taxa such as jellyfish and worms appear at the end of the Proterozoic(1 bya)

  11. Paleozoic Era (543-290 mya) • This era is the beginning of an abundant fossil record • It is broken up into six periods • Cambrian • Ordovician • Silurian • Devonian • Carboniferous • Permian

  12. PaleozoicCambrian●Ordovician●Silurian●Devonian● Carboniferous●Permian • Cambrian Period (543-490mya) • The most commonly preserved Cambrian animal is the trilobite, a crablike invertebrate. • Very little mountain building • Warm oceans • All life in water • Cambrian Explosion • Hard Shells evolved leaving a better fossil record

  13. PaleozoicCambrian●Ordovician●Silurian●Devonian● Carboniferous●Permian • Ordovician Period (490-443mya) • The graptolite is a useful index fossil of the Ordovician. • Appalachian Mountains formed as tectonic plates crashed into one another • All life in water

  14. PaleozoicCambrian●Ordovician●Silurian●Devonian● Carboniferous●Permian • Silurian Period (443-417 mya) • The eurypterid is sometimes called a sea scorpion is a good index fossil . • Evolution of terrestrial (land) • The first land animals included distant relatives of spiders, millipedes, and scorpions.

  15. PaleozoicCambrian●Ordovician●Silurian●Devonian● Carboniferous●Permian • Devonian Period (417-354 mya) • “Age of the Fishes” • Lung fish first appeared (ancestor to amphibians) • First appearance of forests consisting of ferns, giant rushes, and primitive conifers.

  16. PaleozoicCambrian●Ordovician●Silurian●Devonian● Carboniferous●Permian • Carboniferous Period • AKA: Mississippian and Pennsylvanian Periods Mississippian Period: • Crinoids, which look like plants, are actually invertebrate animals related to sea stars. • Foraminifera are one-celled organisms with tiny calcite shells.

  17. PaleozoicCambrian●Ordovician●Silurian●Devonian● Carboniferous●Permian Pennsylvanian Period • First appearance of reptiles, the first true land vertebrates (with backbone) • Large insects including early ancestors of the cockroach

  18. PaleozoicCambrian●Ordovician●Silurian●Devonian● Carboniferous●Permian • Permian Period • Dry climate • Widespread mountain building caused by continental collisions • Mass extinction ended the period and the Paleozoic Era • Marine cephalopods and reptiles were among the survivors

  19. Mesozoic Era (248-65 mya) • The Mesozoic Era “Age of the Reptiles” • Triassic Period • Jurassic Period • Cretaceous Period

  20. MesozoicTriassic●Jurassic●Cretaceous • Triassic Period (248-206 mya) • Dinosaurs made their first appearance on land. • Some of the first dinosaurs were about the size of a cat. • Cephalopods called ammonites are an important index fossil. • During most of the Triassic, almost all of Earth’s land was joined as the supercontinent Pangaea.

  21. MesozoicTriassic●Jurassic●Cretaceous • Jurassic Period • Many larger dinosaurs, including brachiosaurus and Allosaurus • Morphing insects like flies and caterpillars appeared • First birds appeared

  22. MesozoicTriassic●Jurassic●Cretaceous • Cretaceous Period • The largest dinosaurs lived during this period, often exceeding 25 meters in length. (T-rex, Brachiosaurs) • The appearance of flowering plants is perhaps the greatest event. • Modern trees developed. Ex. oak, maple, birch.

  23. MesozoicTriassic●Jurassic●Cretaceous • Continents appeared much as they do today. • Evidence supports asteroid collision caused mass extinction at end of period • This ended the Mesozoic Era (183 million years of dinosaur domination) • Mammals survived the mass extinction

  24. Cenozoic Era (65 mya -present) • Regarded as Earth’s recent history • “The Age of the Mammals” • Divided into three periods: • Paleogene • Neogene • Quaternary

  25. CenozoicPaleogene●Neogene●Quaternary • Paleogene Period • Modern Mountain Ranges:Rockies, the Alps, Himalayas, • Introduction of mammals • Global climate cooled

  26. CenozoicPaleogene●Neogene●Quaternary • Neogene Period • Appearance of grasses lead to explosion of grazing animals such as sheep and cows • Modern forms of the horse, camel, and elephant debuted here

  27. CenozoicPaleogene●Neogene●Quaternary • Quaternary Period • Great temperature fluctuations from warm to cold, leading to increased rates of extinction and evolution • First appearance of humans

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