This document provides an overview of geological time scales and the evolution of Earth. It discusses the units used to measure geological time, from milliseconds to eons. It describes the key events and periods that make up the Precambrian, Paleozoic, Mesozoic, and Cenozoic eras. Methods for constructing the geological time scale are also summarized, drawing on evidence from fossils, radioactive dating, and other sources. Overall, the document serves as a reference for understanding Earth's structural and tectonic development through deep time.

1. Mithun Ray
Department of Geography
Malda College (University of Gour Banga)
E-mail: mithun.ray147@gmail.com
Understanding of Earth’s Tectonic and
Structural Evolution through
Geological Time Scale

2. Units of Time
1000
milliseconds
= 1 second
60 seconds = 1 minute
60 minutes = 1 hour
24 hours = 1day
7 days = 1 week
28, 29, 30 or
31 days
= 1 month
365 or 366
days
= 1 year
12 months = 1 year
10 years = 1 decade
100 years = 1 century
1000 years = 1 millennium

3. ONES
HUNDRED
THOUSAND
LAKH
MILLION
CRORE
BILLION
TRILLION
Numbering System

4. What is Geological Time Scale
 A system of chronological dating that
classifies geological strata in time
 A Calendar for events in Earth History
 A record of the major events and diversity
of life forms present in Earth’s history.

5. Constructing Evidences of
Geological Time Scale
 Field observations
 Fossil records
 Stratigraphic correlations
 Radioactive dating
 Palaeomagnetic orientations
 Orbital revolution of the Earth and
 The rotation of the earth.

6. Major Incidences accounted in Geological
Time Scale
 Mass extinctions,
 Appearance of new species or genera of life,
 Mountain-building movements
 Drifting of continents
 Spreading of ocean floors
 Widespread glaciations
 Dominance of certain species
 Massive migration of life between land and water

7.  From the time of Hutton, scientists were convinced that
the earth was much older than the 6000 years predicted
by the religious scholars.
The oldest rocks found so far on Earth (based on zircon
grains from Australia) have been dated at 4.1-4.2 billion
years.
 Meteorites have also been dated at 4.6 billion years.
Meteorites are considered to be remnants of a plant or
asteroid that originally formed at the same time as the
Earth, so that the Earth’s age is currently estimated to be
4.6 billion years.
 The oldest fossils are preserved remains of
stromatolites, which are layers of lithified blue-green
algae, dating to approximately 3.5 billion years before
present.
Age of our Planet ?
16Table of Contents

8. Units of Geological Time Scale
Duration of half a billion
years (or) more time
EON
ERA
PERIOD
EPOCH
AGE
Duration of Millions
of years
Duration of Tens of
Millions of years
Duration of hundreds of
millions of years
Duration of several hundred
millions of years

9. EON / AEON
Aeon শব্দটি গ্রীক শব্দ “Aion” থেকক একেকে যার অেথ “জীবনকাল”
PhanerozoicArchean
Greek word “Cryptos” means “Hidden”
“”Zoion” means “Living being” / “Life”
Greek word “Phaneros” means “Vissible”
“”Zoion” means “living being” / “life”
Proterozoic
CRYPTOZOIC

10. CRYPTOZOIC
[ Also known as “Pre-Cambrian” ]
 Span of time between 4000 mya and 540 mya
Archean EonProterozoic Eon
### HADEAN EON ###
4600 mya to 4000 mya
As of 2016, International Commission on Stratigraphy
describes its status as “informal”. Geologist Preston
Cloud coined the term in 1972, originally to label the
earliest rocks on earth.

11. (A) ARCHEAN EON
 The oldest era of the earth ( between 4000 mya and 2500 mya )
 The word “archean” comes from the Greek word “arkhe” which means
“beginning” or “ origin”
 The Oldest Rock Formations exposed on the surface of earth ( Canadian
Shield, Baltic Shield, Peninsular India, African Shield etc.)
 Formation of Greenstone Belts
 Origin of life, especially the prokaryotes, bacteria and blue-green algae

12. (B) PROTEROZOIC EON
Between 2500 mya and 540 mya
 Dry and Cold climate
 Origin of Eukaryotic cells and multi-cellular
life
 Occurrence of
earliest known
fossils including
of soft-bodied
marine
invertebrates

13. (C) PHANEROZOIC EON
540 MYA TO PRESENT
OlderYounger

14. Paleozoic
Era
Permian
Period
Carboniferous
Period
Devonian
Period
Silurian Period
Ordovician
Period
Cambrian Period
(I) PALEOZOIC ERA
OlderYounger
Between
540 mya and 245 mya

15. (a) Cambrian Period
Between 540 mya and 505 mya
 Age of trilobites (Marine invertebrates )
Supercontinent Gondwana forms near the South Pole
(note position of present-day Florida)
Existence
of plants was
observed
only as algae
Absence of
land plants.

16. (b) Ordovician Period
Between 505 mya and 438 mya
 Age of Graptolites
First vertebrates originated as jawless fishes
All plants and animals still restricted to water
 Four main
continents:
Gondwana,
Baltica, Siberia
and Laurentia
First
fungi
originated

17. (c) Silurian Period
Between 438 mya and 408 mya
 First land plants appear and land animals follow
Laurentia collides with Baltica and closes Iapetus Sea
Dominance
of Sea lilies,
eurypterids
and land
scorpions
 Origin of
the earliest
Vascular
Plants on
earth

18. (d) Devonian Period
Between 408 mya and 360 mya
 Age of the
Fish
 Pre-Pangea
forms
 Extinction of primitive vascular plants happened
 Origin of modern Vascular plants with true leaves, roots
and stems
 Violent
volcanic
eruptions and
crustal
movements

19. (e) Carboniferous Period
Between 360 mya and 286 mya
It is known
for its coal
deposits
First land
vertebrates
First Reptiles laid eggs with shells in this period.
Highest ever atmospheric oxygen levels seen on earth
was in this period.

20. (f) Permian Period
Between 286 mya and 245 mya
 Pangea
forms.
Reptiles
spread across
continents.
Widespread aridity on one side and Glaciation at the
other side.
Extinction of Palaezoic Plants and invertebrates (251
Mya).

21. Mesozoic Era
Cretaceous Period
Jurassic Period
Triassic Period
(II) MESOZOIC ERA
OlderYounger
Between
245 mya and 66 mya

22. (a) Triassic Period
Between 245 mya and 208 mya
Formation
of Salt,
Gypsum and
red beds
 First dinosaurs, turtles, lizards appear
Pangaea
still in
existence
 Climate arid
Modern
Corals
appeared

23. (b) Jurassic Period
Between 208 mya and 144 mya
Great plant eating dinosaurs were in existence-
“Golden age of dinosaurs”
Appearance
of the first
frogs,
salamanders,
crocodiles,
flying reptiles
and birds
were noticed
Breakup of Pangaea into Gondwana and Laurasia happened
during this period only

24. (c) Cretaceous Period
Between 144 and 66 Mya.
First snakes
appear
First
flowering
plants
Deciduous
trees and
grasses
common
This is the last period of the age of Dinosaurs
 Breakup of Gondwana

25. Cenozoic
Era
Quaternary
Period
Holocene
Pleistocene
Tertiary
Period
Pliocene
Miocene
Oligocene
Eocene
Paleocene
(III) CENOZOIC ERA
OlderYounger
From 66 mya to
Present
EPOCH

26. Tertiary
Period
Pliocene
Miocene
Oligocene
Eocene
Paleocene
OlderYounger
EPOCH
(a) Tertiary Period
Between 65 mya and 2 mya

27. (i) Paleocene
Between 65 mya and 55 mya
First horses appear
 Tropical plants dominate
Climate Tropical

28. (ii) Eocene
Between 55 mya and 38 mya
 Whales, rhinos, elephants and other large mammals
develop.
Reglaciation
in South Pole
 First
Grasses
Appeared

29. (iii) Oligocene
Between 38 mya and 25 mya
 Dogs and cats appear
 Early ancestral
elephants
 Warm but
cooling climate

30. (iv) Miocene
Between 25 mya and 5 mya
 Extensive glaciation in Southern Hemisphere
 Horses and
Mastodons
diverse
First Apes
appeared
Spread of
grasslands as
forests
contracted

31. (v) Pliocene
Between 5 mya and 2 mya
Ice Age begins
Seas restricted
The Grand Canyon Forms
 Cool and dry climate
First known appearance of hominids (human like
primates)

32. Quaternary Period
Holocene
Pleistocene
OlderYounger
EPOCH
(b) Quaternary Period
2 mya to Present

33. (i) Pleistocene
Between 2 mya and 0.01 mya
Ice sheets are predominant- Ice age
 Glacial climate
Four great ice
advances and
retreats
 Modern
humans
develop
Formation of
large scale
Deserts –
Sahara was
formed

34. (ii) Holocene
Since 10,000 years ago
 Rise of human civilization
Beginning of Agriculture
Copper Age
3500 BC
Bronze Age
2500 BC
Iron Age (1200
BC)
Man used iron
implements in
1350 BC

35. Holocene
Epoch
Meghalayan Age
(4200 years ago to the present)
North Grippian Age
(8200 years ago to 4200 years ago)
Greenlandian Age
(11700 years ago to 8200 years ago)

37. We are living in
Meghalayan Age of
Holocene Epoch of
Quaternary Period of
Cenozoic Era of
Phanerozoic Eon

38. Now the question is
How to remember this!
To remember the sequence of ERAs you have to keep
in your mind the following sentence:
Please Pay My Children
Please
Pay
My
Children
Pre-Cambrian
Paleozoic
Mesozoic
Cenozoic
YoungerOlder

39. In case of PERIODs you have to remember
Camels Often Sit Down Carefully Perhaps Their Joints
Creak
Camels
Often
Sit
Down
Carefully
Perhaps
Their Joints
Creak
Cambrian
Silurian
Devonian
Carboniferous
Permian
Triassic
Jurassic
Cretaceous
Ordovician
PaleozoicEra
Mesozoic
Era
YoungerOlder

40. In case of EPOCHs you have to remember
Put Eggs On My Plate, Please Honey
Put
Eggs
On
My
Plate
Please
Honey
Paleocene
Oligocene
Miocene
Pliocene
Pleistocene
Holocene
Eocene
TertiaryPeriodQuaternary
Period
YoungerOlder

43. What if Geologic Time
was the span of your
arm?

44. This Power Point Presentation (PPT) has
been prepared especially for Undergraduate
Students. The materials (Maps, Diagrams
and Images) used in this presentation were
collected and compiled mainly from variours
academic blogs, research papers, books etc.
The author has designed this PPT according
to his convenience to deliver the lecture.

45. THANK YOU