An easy and simple introduction to GTS, helpful for further concepts.

1. DECEMBER
2023
Geological time scale
4.6 BILLION YEARS OF HISTORY

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• The geological time scale is a record of the life
forms and geological events in earth’s history.
• Scientist developed the time scale by studying
rock layers and fossils world wide .
• Radioactive dating helped determine the
absolute division in the time scale.
WHAT IS THE EARTH TIME
SCALE?

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• Eras are subdivided into periods…. Periods are subdivided
in epochs.
Era
Period
Epoch
E+P=EP
DIVISION OF GEOLOGICAL TIME
SCALE

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• A geologic eon is the largest unit of time for the geologic time
scale. Eons are hundreds, even thousands, of years in length. Eons
are made up of shorter eras.
• The Phanerozoic eon is divided into three eras: the Paleozoic,
Mesozoic, and Cenozoic
• Eras: Eons of geological time are subdivided into eras, which are
the second-longest units of geological time.
• Period: This is the basic unit of geologic time. A Period lasts tens
of millions of years, which is the time it takes to form one type of rock
system.
• Epoch: This is the smallest unit of geologic time.
Eon, Era, Period, Epoch

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• Geological time begins with Precambrian Time.
• Precambrian Time covers approximately 88% of Earth’s
history .
Conti……..

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• Pre Cambrian Super Eon- 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.
One Super Eon and Four Eras

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• We are in Holocene Epoch of the Quaternary period of the
Cenozoic Era.
Today…..

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• The age of “Fish”.
• Start: Cambrian period is the first period of the Paleozoic era.
• The “Explosion” of life in the oceans began during this era.
--invertebrates were dominant-Trilobites.
--fish led to the arrival of amphibians.
--coal forming forests grow during this time.
(carboniferous period).
• Ends: Premium period.
Paleozoic Era(ancient life)

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• The “age of Reptiles”.
• Starts: Triassic period.
• Reptiles became the most abundant animal because of their
ability to adapt to the drier climate of the Mesozoic era.
--skin maintains body fluids.
--embryos live in shells.
• Dinosaurs were active in this era.
• Small mammals and birds also appeared in this era.
• Ends: Cretaceous period.
Mesozoic Era(middle life)

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• “Age of Mammals”.
• Starts: Paleocene period.
• Starts 65 million years ago and continues today!!!!
• Ice ages occurred late in this era(Quaternary period).
• Ends: ???
Cenozoic era(modern life)

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14. THANK YOU!
SAMAN TANVEER
Phone
UNKOWN
Email
sanamsam761@gmail.com

15. Reference:
• https://www.slideshare.net/mrco
yleteach/the-geological-time-
scale-70635136.
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