Transcript Geologic Time PowerPoint

A Trip Through Geologic Time
The Geologic Time Scale
1. All of earth’s history is divided up-like
parts of a play- acts, scenes, lines, etc.
 2. We use eons, eras, periods, and epochs.
 3. There are four eras: Precambrian,
Paleozoic, Mesozoic, and Cenozoic.
 4. Precambrian is the longest, lasting 4
billion years. That’s 87% of all of earth’s
history!
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Precambrian Earth
The Beginning of Earth
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1. The solar system began as a huge cloud of gas
and dust 4.6 billion years ago. The cloud collapsed
forming the sun and planets.
2. The denser elements sunk to the core- iron and
nickel. The lighter elements made their way to the
surface as lava from the interior. Scientists believe
the crust was formed by 2.5 billion years ago. The
oldest rocks on earth are called Precambrian
shield and the one in North America is called the
Canadian shield. Two early collisions of
continents formed Laurentia and Rodinia.
Atmosphere
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3. The first atmosphere
was made of Hydrogen
and Helium. Then there
was a thick, poisonous
atmosphere formed by
volcanoes.
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4. Then earth cooled off,
water vapor condensed
into the oceans. There are
theories that water on
Earth may have come
from comet collisions. We
had a warm and humid
atmosphere with storms
producing lightening. This
is where life can begin.
The Precambrian EraThe beginning of life
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1. The first life began somewhere between
3.9 billion years ago and 3.5 billion years
ago. Life began in the oceans. Amino acids
were the first organic molecules. The first
life may have formed at hydrothermal vents
in the deep sea. Single celled bacteria were
the first life on earth. Then came seaweed,
jellyfish, worms, sponges and corals.
Paleozoic EraLife comes onto land
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1.There is abundant life in the seas, the
“Cambrian Explosion.”
2.Trilobites and brachiopods are abundant.
3.In the Ordovician period, there are many
changes in sea level and tectonics continues to
move continents and make mountains. First
jawless fish are in the seas.
4.Silurian period- First plants began to grow on
land and jawed fish evolve.
Paleozoic Events
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The Devonian period is
known as the “Age of
fishes.” First sharks and
the first amphibians
evolve. Amphibians are
organisms that live some
in water and some on
land. They were the first
animals to exist on land.
1.On
land, swamps begin to form and the first insects appear.
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2.Different landmasses
exist until Pangaea forms.
Our own Appalachian
mountains form.
3.In the Carboniferous
period, the first reptiles
evolve. They live only on
land. They have tough
skin with scales or plates
and their eggs have thick
shells. They are quickly
becoming the dominant
animals on earth.
4.By the end of the era,
there were many different
types of trees on land.
The
Permian mass extinction caused the
extinction of 95% of life on Earth. One theory is
that sea level dropped, taking away the marine
environments for the organisms to live.