Download Geologic Time

Geologic Time
Events in Your Life
Construct a timeline of the important events in your life. Be sure to
include all of the events listed below and any other events you
feel are important. Your timeline should be constructed TWO
ways:
1) Numerical Order (use actual dates)
2) Sequential Order (most recent at top)
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•
•
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___When you started second grade
___When you were born
___ When you started kindergarten
___When you learned to ride a bike.
___ When you learned to walk.
___ When you learned to read.
___ When you lost your first tooth.
___ Today’s date.
Geologic Time Scale
• Division of geologic time is based on an
analysis of Earth’s rocks.
• Time units were determined by the age of
fossils found in the rock layer.
• The scale that is created is called the Geologic
Time Scale, it is a record of Earth’s history
from its origin 4.6 billion years ago till today.
Geologic Time Division Sequence
Eon
Era
Period
Epoch
Geologic Time Divisions
• Eon is the longest time unit and is measured
in billions of years.
• Examples: The Archean Eon, the Proterozoic
Eon, and the Phanerozoic Eon
• The Phanerozoic Eon is the time unit we are
currently in and it began 540 million years
ago.
Geologic Time Divisions
• Era is the next longest span of time and is
measured in hundreds of millions to billions of
years.
• Era is defined by the differences in life forms
found in the rock layers and is named based
on the relative age of the fossils.
• Examples: Paleozoic Era, Mesozoic Era,
Cenozoic Era.
Eras are subdivided
into
periods...periods
are subdivided into
epochs
Periods + Epochs =
Era
• Meanings:
– Zoic- “of life”
– Paleo- “old”
– Meso- “middle”
– Ceno- “recent”
FOUR Eras…
• PRE-CAMBRIAN – 88% of earth’s history
• Paleozoic (ancient life)
– 544 million years ago…lasted 300 million yrs
• Mesozoic (middle life)
– 245 million years ago…lasted 180 million yrs
• Cenozoic (recent life)
– 65 million years ago…continues through present day
Precambrian Era
• Atmosphere: Hydrogen and Helium probably
dominant Earth’s atmosphere.
– No oxygen in the atmosphere!!!!
• Plate Tectonics: Numerous volcanic eruptions
released large amounts of gases into the
atmosphere
Precambrian Era
• Age:
– Geologist used radiometric dating to show the
Earth is at least 4.2 billion years olds
• Formations:
– Banded Iron Formations- alternating beds of chert
and iron oxides are now mined for iron.
– Red Beds- sedimentary rocks that are younger
than 1.8 million years are rusty red in color, which
shows that Earth’s was once without oxygen.
Precambrian Era
• Life:
• 3.5 billion years ago the emergence of
cyanobacteria began to release oxygen in the
Cambrian atmosphere.
• Nearly all Oxygen is a
result of photosynthesis.
• Ediacara Fauna- contained a wide variety of
organisms.
Paleozoic Era
• Plate Tectonics:
– The ancient North American continent, Laurentia,
split off from Rodinia, supercontinent, and was
located near the equator.
– Almost completely covered by shallow, tropical
ocean.
– At the end of the Era, Pangaea formed when
Laurasia( North America + Europe) collided with
Gondwana (South America, Africa, India, Australia,
and Antarctica)
Paleozoic Era
• Life:
• Trilobites, Extinct before the dinosaurs
came into existence, Cambrian Period is know as the
“Age of the Trilobites”
• Articulate brachiopods were common.
• Seas were dominated by corals, bryozoans,
brachiopods.
• Fish were dominant predator
• Ferns covered the landscape during the Devonian.
• Amniotes egg evolved and allowed reptiles to
colonize dry land.
Early Fish
Early fish did not have jaws.
Some species of sharks were
in existence at this time.
Early Land Plants
Mosses
Cone bearing plants
Ferns
Paleozoic Era
• Two major mass extinctions:
– Ordovician Period- 75% of all marine genera became
extinct,
• Caused by an episode of global cooling, glaciations.
– Permian Mass Extinction- larges mass extinction in the
history of life.
• Permo-Triasic Extinction Event -95% of all species including
trilobites were impacted.
• Possible reason
– Lowering of sea levels when the continents were rejoined as
Pangaea (convergent boundary)
– Increased volcanic activity (ash and dust)
– Climate changes – cooler climate
Mesozoic Era
• Plate Tectonics:
– Pangaea broke apart
• Life:
– Modern marine fauna present.
• Ex. Crabs, lobsters, shrimps, sponges, modern corals, snails, bony
fish, sharks, aquatic reptiles, and aquatic mammals.
– Dinosaurs dominated the land.
• Gymnosperms or plants that produce seeds, but no
flowers.
– Pine Trees
• Flowering plants appeared during the END of this era.
Dinosaurs
Mesozoic Mammals
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.
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.
Cenozoic Era
• Age:
– Began about 65 million years ago and continues today!!!!!
• Climate was warm and mild.
• Marine animals such as whales and dolphins evolved.
• Plate Tectonics:
– Many mountain ranges formed during the Cenozoic Era
• Alps in Europe and Himalayas in India; Rocky Mountains in
the USA
– Glaciers extended as far south as Ohio and Missouri Rivers.
• Life:
– This era is sometimes called the “Age of Mammals”
– Large mammals and Primates, dogs, cats, etc.
– Homo Sapiens- Humans
Cenozoic Mammals
Flowering Plants were common during the
Cenozoic Era
Geologic Time Divisions
• Periods are defined by the life-forms that were
abundant or became extinct during the time
in which specific rocks were deposited.
• Usually measured in tens of millions of years
to hundred of million of years.
• They are named for the geographic region
were the rocks were first observed.
– Example: Mississippian Period and Jurassic Period
Geologic Time Divisions
• Epochs are the smallest unit of geologic time
and are usually measured in millions of years
to tens of millions of years.
• Epoch’s are based off specific groups of
organisms that have been distinguished.
– Example: Oligocene Epoch is based off the marine
fossils, and the Eocene Epoch is based on
terrestrial plants
Video
• Life after Dinosaurs:
• https://www.youtube.com/watch?v=b7QSwA
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