Earth Science, 10e

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Earth Science, 10e

• Edward J. Tarbuck Frederick K. Lutgens

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Earths History A Brief SummaryChapter 11

• Earth Science, 10e
• Stan Hatfield and Ken Pinzke
• Southwestern Illinois College

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Precambrian era

• 4.5 billion to 540 million years ago
• 88 of Earth's history
• Only sketchy knowledge
• Most Precambrian rocks are devoid of fossils

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Precambrian era

• Precambrian rocks
• Most are buried from view
• Each continent has a "core area" of Precambrian
  rocks called a shield
• Extensive iron ore deposits
• Absent are fossil fuels

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Precambrian shields
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Precambrian era

• Earth's atmosphere
• Primitive atmosphere formed from volcanic gases
• A process called outgassing
• Water vapor, carbon dioxide, nitrogen, and
  several trace gases
• Very little free oxygen
• Water vapor condenses and forms primitive oceans
  as Earth cools

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Precambrian era

• Earth's atmosphere
• Bacteria evolve
• Plants evolve and photosynthesis produces oxygen
• Oxygen content in the atmosphere increases
• By about 4 billion years after Earth formed,
  abundant ocean-dwelling organisms that require
  oxygen existed

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Precambrian era

• Precambrian fossils
• Most common are stromatolites
• Material deposited by algae
• Common about 2 billion years ago
• Microfossils of bacteria and algae have been
  found in chert
• Southern Africa (3.1 billion years of age)
• Lake Superior area (1.7 billion years of age)

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Precambrian era

• Precambrian fossils
• Plant fossils date from the middle Precambrian
• Animal fossils date from the late Precambrian
• Diverse and multicelled organisms exist by the
  close of the Precambrian

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The geologic time scale
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Paleozoic era

• 540 million years ago to about 248 million years
  ago
• First life forms with hard parts
• Abundant Paleozoic fossils
• Early Paleozoic history
• Southern continent of Gondwanaland exists

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Paleozoic era

• Early Paleozoic history
• North America
• A barren lowland
• Seas move inland and recede several times and
  shallow marine basins evaporate leaving rock salt
  and gypsum deposits
• Taconic orogeny, a mountain building event,
  affects eastern North America

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Reconstruction of Earth in early Paleozoic time
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Paleozoic era

• Early Paleozoic life
• Restricted to seas
• Vertebrates had not yet evolved
• Life consisted of several invertebrate groups
• Trilobites
• Brachiopods
• Cephalopods
• First organisms with hard parts, such as shells
  perhaps for protection

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Natural cast of a trilobite
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Appearance and relative abundance of major groups
of organisms
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Paleozoic era

• Late Paleozoic history
• Supercontinent of Pangaea forms
• Several mountain belts formed during the
  movements of the continents
• World's climate becomes very seasonal, causing
  the dramatic extinction of many species

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Formation of Pangaea in late Paleozoic time
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Paleozoic era

• Late Paleozoic life
• Organisms diversified dramatically
• Land plants
• Fishes evolve into two groups of bony fish
• Lung fish
• Lobe-finned fish which become the amphibians
• Insects invade the land
• Amphibians diversify rapidly
• Extensive coal swamps develop

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Mesozoic era

• 248 million years ago to about 65 million years
  ago
• Often called the age of dinosaurs
• Mesozoic history
• Begins with much of the world's land above sea
  level
• Seas invade western North America
• Breakup of Pangaea begins forming the Atlantic
  Ocean

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Mesozoic era

• Mesozoic history
• North American plate began to override the
  Pacific plate
• Mountains of western North America began forming
• Mesozoic life
• Survivors of the great Paleozoic extinction
• Gymnosperms become the dominant trees

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Reconstruction of Earth in the late Jurassic
period
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Mesozoic era

• Mesozoic life
• Reptiles (first true terrestrial animals) readily
  adapt to the dry Mesozoic climate
• Reptiles have shell-covered eggs that can be laid
  on the land
• Dinosaurs dominate
• One group of reptiles led to the birds
• Many reptile groups, along with many other animal
  groups, become extinct at the close of the
  Mesozoic

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Major reptile groups in the Mesozoic era
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Mesozoic era

• Mesozoic life
• Many reptile groups, along with many other animal
  groups, become extinct at the close of the
  Mesozoic
• One hypothesis is that a large asteroid or comet
  struck Earth
• Another possibility is extensive volcanism

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Cenozoic era

• 65 million years ago to the present
• Often called the age of mammals
• Smaller fraction of geologic time than either the
  Paleozoic or the Mesozoic
• North America
• Most of the continent was above sea level
  throughout the Cenozoic era

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Cenozoic era

• North America
• Many events of mountain building, volcanism, and
  earthquakes in the West
• Eastern North America
• Stable with abundant marine sedimentation
• Eroded Appalachians were raised by isostatic
  adjustments

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Cenozoic era

• North America
• Western North America
• Building of the Rocky Mountains was coming to an
  end
• Large region is uplifted
• Basin and Range Province formed
• Re-elevates the Rockies
• Rivers erode and form gorges (e.g., Grand Canyon
  and Black Canyon)

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Cenozoic era

• North America
• Western North America
• Volcanic activity is common
• Fissure eruptions form the Columbia Plateau
• Volcanoes form from northern California to the
  Canadian border
• Coast Ranges form
• Sierra Nevada become fault block mountains

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Cenozoic era

• Cenozoic life
• Mammals replace reptiles as the dominant land
  animals
• Angiosperms (flowering plants with covered seeds)
  dominate the plant world
• Strongly influenced the evolution of both birds
  and mammals
• Food source for both birds and mammals

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Cenozoic era

• Cenozoic life
• Two groups of mammals evolve after the reptilian
  extinctions at the close of the Mesozoic
• Marsupials
• Placentals

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Cenozoic era

• Cenozoic life
• Mammals diversify quite rapidly and some groups
  become very large
• e.g., Hornless rhinoceros, which stood nearly 16
  feet high
• Many large animals became extinct
• Humans evolve

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End of Chapter 11