Geologic Time Scale Spring 2015 8th Grade Geologic Time Scale The geologic time scale is a record of the major eventsand diversity of life forms present in Earths history. The geologic time scale began when Earth wasformed and goes on until the present. At the end of each era a mass extinction occurred,many kinds of organisms died out, although therewere other extinctions going on during eachperiod of geologic time. Using the fossil record, paleontologists havecreated an idea of the different types of commonorganisms in each geologic period. Divisions of Geologic Time
Eras are subdivided into periods...periods aresubdivided into epochs. Era Period Epoch E + P = EP Divisions of Geologic Time
Various models, diagrams, and pictures can be used toillustrate the vastness of time involved in and to showthe diversity of life evident across geologic time. Cretaceous- Flowering Plants, Major extinction of Dinosaurs
Jurassic- Early birds & Mammals, abundant dinosaurs Triassic- Lots of Conifers, 1st Dinos, 1st Mammals Mesozoic Era Paleozoic Permian- Mass Extinction of marine animals like trilobites
Devonian Early trees Silurian-Early land plants Ordovician-Early Fish Paleozoic Precambrian Proterozic- SingleMulticellular
Organisms. ArcheanOldest fossils, bacteria & sinlge celled organisms Precambrian Precambrian Era 88% of the History of Earth
4.6 Billion Years Ago 450 Million Years Ago (Color in 27 wedges) Precambrian Era Earth's first era of time.
5 major events occurred during this era: (1) the formation of the Sun and light (2) the creation of the Earth (3) the creation of the atmosphere through volcanic out-gassing (4) the creation of the oceans (5) the creation of life Precambrian Era Began with simple life forms such as bacteria and simplealgae. There was a rise of simple organisms such as jellyfish andsea worms by the end of the era. Few fossils because the life forms were soft-bodied and hadno hard skeleton. Precambrian Era Geological Events: Earth Began Biological Events:
Bacteria Appear Soft-Bodied Multi-CellularOrganisms Appear Paleozoic Era 544 Million Years Ago 244 Million Years Ago
Ancient Life 544 Million Years Ago 244 Million Years Ago (Color in 3 wedges) Paleozoic Era Animal Life:
Began with the earlyinvertebrates, such astrilobites and brachiopods. Continued to develop earlyvertebrate fish, arachnidsand insects. Later came the firstamphibians and near theeras end the reptilesbecame dominant. Paleozoic Era Plant Life:
Early land plants included simple mosses, ferns, and then cone-bearing plants. By the end of the era, seed plants were common. The mass extinction that ended the era causedmost marine invertebrates as well as amphibiansto disappear. Paleozoic Era Geological Events: Biological Events:
Shallow seas covermuch of the land Coral reefs develop Pangaea forms AppalachianMountains form Biological Events: Great explosion of invertebrates in the sea (Trilobites appear) Land plants appear Insects and spiders appear Age of fish begins First reptiles appear Trilobites become extinct Mesozoic Era 245 Million Years Ago 65 Million Years Ago Middle Life
(Color in 1 wedges) Mesozoic Era Reptiles were the dominant animals of this era, including the various dinosaurs. Small mammals and birds also appeared. Toward the end of the era, flowering plantsappeared and the kinds of mammals increased. The mass extinction that ended the era caused thedinosaurs to become extinct. Mesozoic Era Geological Events: Hot, dry conditions dominate Pangaea
Pangaea splits Widespread volcanic activity Biological Events: Dinosaurs appear Largest dinosaurs thrive Dinosaurs become extinct Mammals, birds and flowering plants appear Cenozoic Era 65 million years ago - Today Recent Life
(Color in a wedge) Cenozoic Era Many mountain ranges formed
New mammals appeared while others became extinct. Mammals had to evolve to adapt to different environments. The diversity of life forms increased. Flowering plants became most common. Humans are also part of the most recent period of thisera. Many mountain ranges formed ex. Alps in Europe, Himalayas in India & RockyMountains in the USA Cenozoic Era Geological Events: Rocky Mountains and Himalayas form
Continental glaciers cover Antarctica Ice age ends Biological Events: First grasses appear Mammals, flowering plants, and insectsdominate the land Humans appear