GEOLOGIC TIME

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GEOLOGIC TIME

• Chapter 5

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PrecambrianEon

• 4.5 billion years ago, the Earth was born.
• Consider that the Earth formed, life arose
• - the first tectonic plates arose and began to
  move
• - eukaryotic cells evolved
• - the atmosphere became enriched in oxygen
  and
• - just before the end of the Precambrian,
  complex multicellular organisms, including the
  first animals, evolved

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Earth is constantly changing

• 1700 James Hutton began to question about
  changes of Earth he came up the hypothesis about
  changing Earth over time.
• UNIFORMITARIANISM Huttons theory
• Earth is an always-changing place
• The same forces of change at work today were at
  work in the past.

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Alfred Wegener

• German scientist that proposed a hypothesis about
  continental drift in 1912.
• He called the landmass Pangaea
• His ideas led to the theory of Plate Tectonics
• Plate tectonics states that Earths lithosphere
  is made up of huge plates that move over the
  surface of Earth

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Geologic Time Scale

• It divides Earths history into intervals of time
  defined by major events or changes on Earth
• Divisions of Geologic Time
• Eon the largest time, Earth has 4 eons
• Era Eons are divided into eras Paleozoic,
  Mesozoic and Cenozoic
• Period - Each era is subdivided into a number of
  periods
• Epoch The periods of the Cenozoic, are further
  divided into epochs

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Precambrian Time

• Make up almost 90 percent of Earths history
• Division of Precambrian Time
• Hadean Eon
• Archean Eon
• Proterozoic Eon

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Hadean time

• 4.5 to 3.8 billion years ago
• the Solar System was forming

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Archaean

• 3.8 to 2.5 billion years ago
• With a reducing atmosphere of methane, ammonia,
  and other gases
• The Earth's crust cooled enough that rocks and
  continental plates began to form.

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Proterozoic Eon

• 2.5 billion to 543 million years ago
• Stable continents first appeared and began to
  accrete, a long process taking about a billion
  years
• In the Middle Proterozoic comes the first
  evidence of oxygen build-up in the atmosphere

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Phanerozoic Eon

• The majority of microscopic organisms, algal,
  fungal, plant and animal lived.
• approximately 544 million years ago
• Division
• Paleozoic Era
• Mesozoic Era
• Cenozoic Era

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Paleozoic Era

• 544 to 248 Million Years Ago
• Also known as the Ancient Life
• multicellular animals underwent a dramatic
  explosion in diversity
• At the other end of the Paleozoic, the largest
  mass extinction in history wiped out
  approximately 90 of all marine animal species
• During the Paleozoic there were six major
  continental land masses each of these consisted
  of different parts of the modern continents.

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Division of Paleozoic Era

• Cambrian Period
• Ordovician Period
• Silurian Period
• Devonian Period
• Carboniferous Period
• Permian Period

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Mesozoic Era

• 248 to 65 Million Years Ago
• Whose name means middle life
• The Mesozoic is divided into three time periods
• the Triassic (245-208 mya)
• the Jurassic (208-146 mya)
• and the Cretaceous (146-65 mya).

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Cenozoic Era

• 65 Million Years to the Present
• The name means recent life
• The Cenozoic is the most recent of the three
  major subdivisions of animal history
• Sometimes called the Age of Mammals

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Division

• Tertiary Period
• Quaternary Period stretches from 2 mya to the
  present
• Most of this period has been a series of ice
  ages, with much of the planet covered in thick
  sheet of ice
• Fossils of the modern humans are also from this
  period. They are about 100,000 years old.