The document outlines the geological time scale which is used to describe the 4.6 billion year history of Earth. It is divided into eons, eras, periods, and epochs based on studying rock layers and fossil records. The current eon is the Phanerozoic which began over 541 million years ago and is divided into the Paleozoic, Mesozoic, and Cenozoic eras describing the rise of ancient life, age of reptiles, and modern life including mammals respectively. The document provides details on the major life forms and events of each period within these eras.

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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