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The Geological Time Scale

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Title: The Geological Time Scale


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Earths History __________________________________
__________________________________________________
_______________________ Geologic Time
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What is the Earths time scale?
  • The Geological time scale is a record of the life
    forms and geological events in Earths history.
  • Scientists developed the time scale by studying
    rock layers and fossils world wide.
  • Radioactive dating helped determine the absolute
    divisions in the time scale.

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Divisions of Geologic Time
  • Eras are subdivided into periods...periods are
    subdivided into epochs.

Era
Period
Epoch
E P EP
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Divisions of Geologic Time
  • Geological time begins with Precambrian Time.
    Precambrian time covers approximately 88 of
    Earths history.

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FOUR Eras
  • PRE-CAMBRIAN 88 of earths history
  • Paleozoic (ancient life)
  • 544 million years agolasted 300 million yrs
  • Mesozoic (middle life)
  • 245 million years agolasted 180 million yrs
  • Cenozoic (recent life)
  • 65 million years agocontinues through present day

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Today
  • Today we are in the Holocene Epoch of the
    Quaternary Period of the Cenozoic Era.

Which unit is the largest? Which unit is the
smallest?
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Paleozoic Era (Ancient Life)
  • Cambrian - 1st period of the Paleozoic Era. Age
    of the Trilobites
  • Cambrian Explosion sudden increase of diverse
    life in the oceans
  • Most of the continents were covered in warm,
    shallow seas.
  • Invertebrates were dominant - Trilobites
  • Fish emerged during this time
  • Fish led to the arrival of amphibians
  • End of the Paleozoic era called the Age of
    Amphibians
  • Early land plants including mosses, ferns and
    cone-bearing plants.
  • The early coal forming forests were also formed
    during this time.

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Paleozoic Era
  • Much of the limestone quarried for building and
    industrial purposes, as well as the coal deposits
    of western Europe and the eastern United States,
    were formed during the Paleozoic.
  • The Cambrian (beginning) opened with the breakup
    of the world-continent Rodinia and closed with
    the formation of Pangaea, as the Earth's
    continents came together once again.
  • This event is thought to have caused the climate
    changes that led to mass extinction event.
  • The Appalachian mountains were formed during this
    time.

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Paleozoic Era
  • At the end of the Paleozoic, the largest mass
    extinction in history wiped out approximately 90
    of all marine animal species and 70 of land
    animals.
  • Possible causes of this Mass Extinction Event
  • Lowering of sea levels when the continents were
    rejoined as Pangaea (convergent boundary)
  • Increased volcanic activity (ash and dust)
  • Climate changes cooler climate

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Trilobites
  • Lived in Earths ancient seas
  • Extinct before the dinosaurs came into existence
  • Cambrian Period is know as the Age of the
    Trilobites

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Brachiopods
  • Marine animals that resemble clams.

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Early Fish
Early fish did not have jaws. Some species of
sharks were in existence at this time.
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Frilled Shark that was found in Japan in January
2007. This shark was considered a living fossil
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Early Land Plants
Mosses
Cone bearing plants
Ferns
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Mesozoic Era Middle Life
  • At the beginning of this era the continents were
    joined as Pangaea.
  • Pangaea broke up around the middle of this era.
  • Reptiles became the most abundant animals because
    of their ability to adapt to the drier climate of
    the Mesozoic Era.
  • Skin maintains body fluids
  • Embryos live in shells

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Mesozoic Era
  • Dinosaurs were also very active in this era.
  • First small dinosaurs appeared in the Triassic
    Period.
  • Larger and more abundant dinosaurs appeared in
    the Jurassic Period.
  • Small mammals and birds also appeared during this
    era.
  • The mammals were small, warm-blooded animals.
    Hair covering their bodies.
  • These characteristics help them survive in
    changing environments.

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Mesozoic Era
  • The main plant life of this time were Gymnosperms
    or plants that produce seeds, but no flowers.
  • Pine Trees
  • Flowering plants appeared during the END of this
    era.

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Mesozoic Era
  • This era ended with a mass extinction event about
    65 million years ago.
  • Many groups of animals, including the dinosaurs
    disappeared suddenly at this time.
  • Many scientists believe that this event was
    caused by a comet or asteroid colliding with the
    Earth.

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Mesozoic Era Mass Extinction Event
  • Asteroid or Comet collides with Earth.
  • Huge cloud of smoke and dust fills the air
  • Blocks out sunlight
  • Plants die
  • Animals that eat plants die
  • Animals that eat plant-eaters die.
  • However, not all forms of life died during this
    event. Many animals that you see today are
    descendants from the survivors of this extinction
    event.

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Dinosaurs
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Mesozoic Reptiles
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Mesozoic Mammals
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Mesozoic Plants
Flowering plants evolved towards the end of the
Mesozoic Era.
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Cenozoic Era Recent Life
  • Began about 65 million years ago and continues
    today!!!!!
  • Climate was warm and mild.
  • Marine animals such as whales and dolphins
    evolved.
  • Mammals began to increase and evolve adaptations
    that allowed them to live in many different
    environments land, air and the sea.
  • Grasses increased and provided a food source for
    grazing animals
  • Many mountain ranges formed during the Cenozoic
    Era
  • Alps in Europe and Himalayas in India Rocky
    Mountains in the USA

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Cenozoic Era
  • Growth of these mountains may have helped to cool
    down the climate
  • Ice Ages occurred late in the Cenozoic Era
    (Quaternary Period).
  • As the climate changed, the animals had to adapt
    to the rise and fall of the oceans caused by
    melting glaciers.
  • This era is sometimes called the Age of Mammals

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Cenozoic Era
  • Marine animal examples
  • Algae, Mollusks, Fish and Mammals
  • Land animal examples
  • Bats, Cats, Dogs, Cattle and Humans
  • Humans are thought to have appeared around 3.5
    million years ago (during the most recent period
    Quaternary).
  • Flowering plants were now the most common plant
    life.

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Cenozoic Mammals
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Flowering Plants were common during the Cenozoic
Era
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