Transcript The Geologic Timeline

The Geologic Timeline
Geologic Time Scale
► The
division of Earth’s
history is divided into
units of time, based on
the fossil records
contained in the rocks.
► The Geologic Time
Scale is broken-up into
four major divisions…
► Eons, Eras, Periods,
Epochs
Eons of Geologic Time
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These are the largest
division
They are measured in
hundreds of millions to
billions of years
There are four of them
 Hadean
 Archaean
 Protoerozoic
 Phanerozoic
Hadean, Archaen and
Proterozoic are often
classified as “Precambrian
Time”
Precambrian Time
►
The Hadean Eon (4.6 – 3.8 Billion Years Ago)
 Earth cooled and formed from a cloud of gas,
and from asteroid collision.
 Iron and Nickel sank to the core.
 Oxygen and Silicon rose to the surface.
 Earth’s solid surface is created
 (Hadean is sometime not recognized)
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The Archaean Eon (3.8 – 2.5 Billion Years Ago)
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An early atmosphere develops
Ancient oceans develop
Continent-building occurs
The first forms of life (bacteria) arrive
The Proterozoic Eon (2.5 Billion – 543 Million
Years Ago)
 Single, super continent of Rodinia forms
 Atmosphere becomes oxygen-rich
 Multi-cellular plant and animal life develops
Eras of Geologic Time
► The
Eras are the
second longest division
of the geologic time
scale
► They are measured in
hundreds of millions of
years
► They are defined by
the life forms found in
the rocks as fossils
The Phanerozoic Eon, and the “Big
Three” Eras
►
The fourth Eon (Phanerozoic) contains
the only real Eras...
 The Paleozoic Era
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An explosion of life forms
Fish develop
Life comes on land
Giant insects
 The Mesozoic Era
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Pangaea is formed
Reptiles and Dinosaurs thrive
 The Cenozoic Era
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Flowers, Birds and Mammals thrive
Pangaea breaks up
Volcanoes and Mt. Building occur
Remember that an Era is defined by the
different life forms found as fossils in the
rocks.
Periods of Geologic Time
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Geologic Periods are
defined by the life forms
that were abundant, or
became extinct.
Each Era is broken-down
into multiple Geologic
Periods, based on the life
forms that thrived or died
They are measured in
millions to tens of millions
of years
Epochs of Geologic Time
► These
are the smallest
of the major divisions
► They are measured in
millions of years to
tens of millions of
years
► They are distinguished
by different groups of
organisms
So where are we…
► We
are in the…
 Phanerozoic Eon…
 The Cenozoic Era…
 The Quaternary
Period…
 The Holocene Epoch.
A “graph” representing Geologic
Time
►
Label the…
 The Hadean Eon,
 Archaean Eon,
 Proterozoic Eon
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Label all three of the early
Eons as “Pre-Cambrian”
Time.
Label the…
 Paleozoc Era
 Mesozoic Era
 Cenozoic Era
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Label all three of these
Eras as the Phanerozoic
Eon.
A “football field” representing
Geologic Time