The Geological Time Scale

MHRD
NME-ICT
THE GEOLOGICALTHE GEOLOGICAL
TIME SCALETIME SCALE
By
Prof. A. Balasubramanian
Centre for Advanced Studies in Earth Science
University of Mysore, India

MHRD
NME-ICT
MHRD
NME-ICT
 Introduction
 The Geologic Time Scale
 Precambrian Era
 Paleozoic Era
 Mesozoic Era
 Cenozoic Era
 Conclusion.
Table of Contents

MHRD
NME-ICT
After attending this lesson, the user would be
able to highlight the various periods of the
earth’s history.
The origin and evolution of life that have
happened during different periods will also be
known.
Objectives

MHRD
NME-ICT
 While studying the physical geology and history of the planet
earth, it is necessary to know about the Geological Time Scale,
in detail.
 The study of the geological time scale is necessary to every
student of earth, atmospheric and all life sciences.
 The origin and evolution of the Earth took place over a period
of billions of years.
 The evolution of life on earth is also a part of that prolonged
Earth’s history. It is a fact that the planet earth has evolved as
one of the planets from the common nebulae.
Introduction
(…Contd)

MHRD
NME-ICT
 Due to this reason, the age of the earth is also related to the
age of the Solar System. From the Big-Bang theory, till today,
the time span or time-frame of the Earth’s evolution is very
extensive.
 The periods of remarkable development in the evolution of
life, the stages in the evolution of continents, the stages in the
evolution of ocean basins, the origin and evolution of life on
earth, and their proliferations or mass-extinctions, are
represented in the form of geological records on the surface
rocks and sediments all, over the world.
 They clearly show the fossilized evidences of the past life and
environment.
Introduction
(…Contd)

MHRD
NME-ICT
 The whole historical past of the earth from the origin of life
till date are classified into eras, periods, epochs and ages.
 The time scale which spreads the earth’s geological history
into such divisions and sub-divisions is known as the
Geological Time Scale.
 This time scale is very wide and cannot be mathematically
shown in a small graph.
 This lesson highlights the importance and details of the
geological time scale.
Introduction

MHRD
NME-ICT
The Geological Time Scale was constructed using the evidences
collected from various sources, like
Field observations
Fossil records
Stratigraphic correlations
Radioactive dating
Paleomagnetic orientations
Orbital revolution pattern of the Earth and
The duration of the daily rotation of the earth around its axis.
These evidences have indicated that there were several major
incidences that happened in the history of the earth, during
various stages and ages.

MHRD
NME-ICT
Some of the major events like
 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 are all
considered while accounting the geologic time scale.
These have shown very interesting aspects and features.

MHRD
NME-ICT
 The changes that occurred throughout the history of the
earth stand well in the form of distinct and contrasted
features.
 They all have shown orderly and uniform operation of
natural systems, in the past.
 The early history of the earth differs in character from
late history.
 Due to this reason, there was a need to divide the units
of time in terms of billions of years or millions of years.
(…Contd)

MHRD
NME-ICT
 The early history of the planet is described in billion-year
units of time.
 The late history of the earth is described in million-year
units of time. And finally, the recent time is described in
1000’s of year units.
 Several experts attempted to reconstruct the schedule of
events of profound changes that happened at various stages
by considering the aspects of the earth’s physical systems.
 The geological time scale was formulated with care for
universal application.
(…Contd)

MHRD
NME-ICT
The understanding of the geologic time scale is necessary while
studying the geology of the earth. In this lesson, the following
aspects of the Geologic Time Scale are highlighted:
1.HISTORY OF THE TIME SCALE
2.THE GEOLOGICAL TIME SCALE
3.PALEOZOIC ERA
4.MESOZOIC ERA
5.CENOZOIC ERA
Each one of these major sections, is classified into several
chronological sequences and divisions.

MHRD
NME-ICT
 Everything we do has got a time-frame. The life span is
limited to some years.
 Time is not just a unit or feature or phenomenon of the
present.
 Was the earth originated along with the Universe or at a
later stage? How long is the history of the earth?
 There are several such questions which are to be
answered while studying the history of the earth.
(…Contd)
History of The Time Scale

MHRD
NME-ICT
 To answer all these questions, scientists have constantly
tried and searched the clues and sequences on the Planet
from its origin.
 They studied the Solar System and its evolution, very
meticulously.
 It is the change in the components of the sedimentary
sequences that made people to know about the duration,
and that has provided the basis for the measurement of
the past with time units.
(…Contd)

MHRD
NME-ICT
The change that was considered were,
 The Emergence or coming into existence of something new,
 The alteration of something that was already existing
(or)
 The disappearance (or) loss of something, widespread, in a
region.

MHRD
NME-ICT
The Passage of Time
 The passage of time can be related to a series of events.
 In order to construct the history of past events, one must
determine how much time elapsed between the events
and how long it took for the events to occur.
 Time is also marked by certain characteristic or unique set
of events.
 When we list the events in an order in which they took
place, we establish a chronological sequence of all the
events.

MHRD
NME-ICT
Two Kinds of Clocks
The measurement of time is accomplished with two
kinds of clocks known as
A.mechanical clocks and
B.natural clocks.
Our wall clock (or) our wrist watch is a mechanical
clock.
(…Contd)

MHRD
NME-ICT
There are several kinds of natural clocks and calendars
used to refer the events of the past to the present.
For understanding the past geological events, geologic
clocks were used.
They are:
1.Radioactive clocks (or the atomic clocks) and
2.Stratigraphic units correlated with Fossil population.
Two Kinds of Clocks

MHRD
NME-ICT
 Radioactive disintegration is an accurate phenomena
to find out the date of earth’s naturally occurring
materials.
 The life of the radioactive element is expressed in
terms of its half-life, which is the time required for half
of any original amount of the material to be
transformed.
Radioactive Disintegration
(…Contd)

MHRD
NME-ICT
 The actual rate of decay has been found to be
entirely independent of environmental factors.
 This is a major advantage for adopting and accepting
the measurements.
Radioactive Disintegration

MHRD
NME-ICT
 Using this method, the relative ages of most of the
rocks of the earth’s surface were dated during the early
1800’s and late 1700’s.
 By following the principles of super position, fossil
correlation and relative dating of atomic clocks in rocks,
the Geologic Time Scale was prepared in 1833 and
1905.
 The original idea has come from the works of Johann
Lehmann (1719-1767).
Relative Ages of The Rocks
(…Contd)

MHRD
NME-ICT
 Continuous Annual deposition of sediments with life
remains in water bodies can create sequential beds of
sediments containing the fossils of animals and plants.
 These are called as stratigraphic sequences.
 These stratigraphic sequences were correlated to
evaluate the evolutionary trend of ancient life and the
geological formations.
Relative Ages of The Rocks

MHRD
NME-ICT
Scale for The Entire Earth’s History
 The geologic time scale is a reference scale for the
entire Earth’s history.
 It helps to understand the entire history of the earth
into workable units.
 Based on all the available evidences, the earth is found to
be around 4500 million years old.
 In other words, the earth is almost 4.5 billion years old,
since the starting point of the hot universe, which gave
birth to the galaxies.

MHRD
NME-ICT
 The Hot original matter of the Universe is the starting
point of the time scale. About 15.0 billion years ago, the
hot Universe matter, with unimaginable temperature,
was believed to have been in existence.
 We know that the Universe cannot be younger than its
products.
 It must be older than the individual galaxies, older than
the earth and older than all the chemical elements.
(…Contd)
The Geologic Time Scale

MHRD
NME-ICT
The Geologic Time Scale
 Evidences indicate that an important event occurred
about 10 to 12 billion years ago, that this mass got
expanded and exploded.
 Due to this, the galaxies got separated from this mass
and in a similar process, the stars and their planets was
separated.
 If the Universe just keeps on expanding, then the
galaxies will get farther and farther apart until each one
is ‘alone’ in space.

MHRD
NME-ICT
 A rough calculation shows that this would have been
about 10 to 12 billion years ago.
 The Big-Bang theory also states this globe of energy
and its sequential release of galaxies, very clearly.
 Formation of Galaxies, Stars and Planets happened
from this hot universe.
 About 10 billion years ago the first generation galaxies
started to spiral around and got released one after the
other.
Age of The Galaxy
(…Contd)

MHRD
NME-ICT
 The Milky Way Galaxy got released at about 6 billion
years ago.
 From this mass, the Sun and the other members of the
Solar System got originated at about 5 billion years ago.
 In an accurate estimate, it is found, that the Sun and its
Planets were born around 4.56 billion years ago.
Age of The Galaxy

MHRD
NME-ICT
Dating The Periods
 Millennium, century and decade are the references made to
denote the periods used in these time units.
In addition, the divisions in the time scale were made into
the following units:
a) EON is the mega unit comprising a duration of half a billion
years (or) more time
b) ERA is used to refer the duration of several hundred
millions of years.

MHRD
NME-ICT
Dating The Periods
 PERIOD is used to cover hundreds of millions of
years.
 EPOCH is used to denote the duration of Tens of
Millions of years and
 AGE is used to cover a duration of Millions of years in
the earth’s history.

MHRD
NME-ICT
Dividing The Geologic Time
The Geologic Time Scale of the earth is divided into two
major eons as:
Phanerozoic eon
Cryptozoic eon.
The term phanerozoic was derived from the Greek
word “Phoneros “ meaning “ Visible”, and Zoo means
life.
(…Contd)

MHRD
NME-ICT
Dividing The Geologic Time
 The term Phanerozoic was used to refer the eon of visible
life on earth.
 The term azoic was used to denote the eon of “no life” on
earth.
 The term CRYPTOZOIC was derived from the Greek
word Crypto which means Hidden and Zoo means life.
 Cryptozoic eon refers to the eon of hidden life.

MHRD
NME-ICT
Eons and Eras
These two Eons are divided into various ERAS. The geologic
time of the earth is divided into five major eras as:
a.CENOZOIC ERA - (Greek: Kaines – Recent, Zoo-life) - 65 Mya
to the present
b.MESOZOIC ERA - (Greek: Mesos – Middle, Zoo-life) Age of
Reptiles and Ammonoids - 245 – 66.4 Mya
c.PALEOZOIC ERA – (Greek: Paleos – ancient, Zoo-life) - 540 –
245 Mya
d.PRECAMBRIAN ERA (OR PROTEROZOIC ERA)-Greek: Protero
– Primitive, Zoo-life) 4500 – 540 Mya.
e.ARCHAEAN ERA.

MHRD
NME-ICT
The short-form of millions of years is Mya. The duration
of PRECAMBRIAN ERA refers to the Span of time
between 4500 Mya – and 540 Mya.
It is further divided into two eras as:
1.PROTEROZOIC ERA - from 2500 Mya to 540 Mya
2.ARCHAEAN ERA - from 4500 Mya to 2500 Mya.
These are further divided into various periods.
Precambrian Era

MHRD
NME-ICT
 The Precambrian era is the oldest era of the earth.
 The period between the formation of Earth around
4600 Mya to the beginning of Cambrain period (about
542 Mya ago) is named as the Precambrian Era.
 It accounts for 88% of the total geologic time.
 Very little is known about the Earth’s history during
this period
The Precambrian Era
(…Contd)

MHRD
NME-ICT
 The fossil record of Precambrian period is very
poor.
 The fossils present like stromatolites are of limited
biostratigraphic use.
 Details of plate motions and other tectonic functions
are hazily known in the Precambrian.
 It is the base period of the entire geological history
of the earth.
The Precambrian Era

MHRD
NME-ICT
The notable observations of Precambrian period are:
 First appearance of life on earth
 Tectonic Plates were present and began moving
 Atmosphere became enriched in oxygen
 Dry and cold climate to warm and moist
conditions prevailed on the earth.
Precambrian Period
(…Contd)

MHRD
NME-ICT
 This is the earliest of all the geologic ages.
 It is further divided into Proterozoic Era
(2500-540 Mya) and Archean Era (3960-2500 Mya).
 The age of the earth is probably about 4500 Mya.
Precambrian Period

MHRD
NME-ICT
The Archaean Era
The Archean Era is the oldest era of the earth between
3960 Mya and 2500 Mya. The significant observations of
this period are:
Extensive mountain-building,
Formation of banded iron ores and Greenstone belts,
Existence of shallow seas,
Accumulation of free oxygen, and Origin of life, especially
the prokaryotes, bacteria and blue-green algae.

MHRD
NME-ICT
The Proterozoic Era (2500-540 Mya) is the second era after
Archaen era. The significant observations of this period are:
Dry and Cold climate,
Warm and moist conditions,
Origin of Eukaryotic cells and multicellular life Occurrence of
earliest known fossils including of soft-bodied marine
invertebrates,
Origin of Sponges,
Cnidarians and Annelids.
The Proterozoic Era

MHRD
NME-ICT
 The duration of PALEOZOIC ERA is the time of
Ancient life.
 This is the second major era of earth’s history.
 It is the age of Invertebrates.
 This era has the span over a period between 540
Mya and 245 Mya.
Paleozoic Era
(…Contd)

MHRD
NME-ICT
 It is further divided into six periods as:
 Permian - 286 -245 Mya
 Carboniferous - 360-286 Mya
 Devonian - 408-360 Mya this is the Age of fish
 Silurian - 438 – 408 Mya
 Ordovician - 505 – 438 Mya this is the Age of Graptolites
 Cambrian - 540 – 505 Mya this is the Age of trilobites
These are very important periods in the earth’s history. Each period
has shown a very significant change in the planets constituents.
Paleozoic Era

MHRD
NME-ICT
The Cambrian Period
The Cambrian Period is spread between 540 and 505
Mya. This the period of abundant life on Earth, after the
Proterozoic. The significant observations of Cambrian
period are:
 Prevalence of Mild climate,
 Extensive seas,
 Spilling over continents,
 Shelled Marine invertebrates
 Explosive growth of Eukaryotic organisms, (…Contd)

MHRD
NME-ICT
The Cambrian Period
(…Contd)

MHRD
NME-ICT
The Cambrian Period
 This period is marked by the absence of land plants.
 There was a significant prosperity of life in the oceans
than lands, during this period.
 During this period the continents had a soil crust and
were resembling deserts.

MHRD
NME-ICT
The Cambrian Period is followed by the Ordovician period.
It has the duration between 505 and 438 Mya.
The significant observations of the Ordovician period are:
Mild climate-Adaptive Radiation (Ordovician radiation)
Shallow seas retreating from land and spreading back all
plants and animals still restricted to water,
the first vertebrates originated as jawless fishes
Invertebrates dominated,
The Ordovician Period
(…Contd)

MHRD
NME-ICT
The First fungi originated during this period.
(…Contd)

MHRD
NME-ICT
 Invasions of land by plants started.
 The Sea levels were high during Ordovician, the First
known marine transgressions occurred during this period.
 The Southern Continents were collected into a single land
mass.
 It was named as Gondwana Land.
 The world’s major mountain-building activity happened
during this period.

MHRD
NME-ICT
 The Ordovician period is followed by the Silurian Period.
 It is spread between 438 Mya and 408 Mya. The
significant observations of the Silurian period are:
 The world has seen a mild climate, and experienced a
stable and warm temperature during this period.
 The continents were generally flat and flooded.
The Silurian Period
(…Contd)

MHRD
NME-ICT
 The notable mountain building occurred in Europe.
 The rise of fishes and reef building corals were originated
in this period.
 There was marked abundance of shell-forming sea
animals, dominance of Sea lilies, eurypterids and land
scorpions, and invasion of land by arthropods.
(…Contd)
The Silurian Period

MHRD
NME-ICT
 In this period, the earth has found the origin of the earliest
Vascular Plants.
 The modern group of Algae and Fungi got evolved during
this period.
 Almost 60% of the marine species were wiped out at the
base of the Silurian period.
 This was the first period which has shown macrofossils of
extensive terrestrial biota.
The Silurian Period

MHRD
NME-ICT
The Silurian period is followed by the Devonian Period. It is
spread between 408 Mya and 360 Mya. The significant
observations of the Devonian period are:
Violent volcanic eruptions and crustal movements, prevalent
folding, mountain-building activities and drier Climate.
The seas were covering most of the land.
This is the age of fishes, sharks and rays.
The Devonian Period
(…Contd)

MHRD
NME-ICT
 The fishes move into the open seas. Lunged fishes and
amphibians appeared in this Devonian period.
 The Mollusks were abundant.
 It has noticed the extinction of primitive vascular plants.
 Origin of modern Vascular plants with true leaves, roots
and stems were seen from this period.
 The Earth appeared to look green. Some plants started to
produce seeds rather than spores.
The Devonian Period

MHRD
NME-ICT
The Carboniferous Period
The Devonian Period is followed by the carboniferous period.
It is spread between 360 Mya and 286 Mya.
The significant observations of the Carboniferous period are:
 It is known for its coal deposits, lime stones and Grit stones.
 The Hercynian orogenic movements were stared.
 There was abundant of life on land and water.
 The earth has seen Large Primitive Trees, First land vertebrates, and
Sea Invertebrates. (…Contd)

MHRD
NME-ICT
 There was a prevalence of Foraminifers, Bryozoans,
Brachiopods, Cephalopods, Blastoids, Crinoids and Corals.
 The Brachiopods are the zone fossils of Carboniferous
period.
 The Lamellibranchs and winged insects were important
fauna.
 The Swamp forests with ferns were existing.
(…Contd)

MHRD
NME-ICT
 The Lepidodendron and Sigillaria were the prominent
flora of the world in this period.
 The world’s First Reptiles laid eggs, with shells, in this
period.
 The highest ever atmospheric oxygen levels seen on
earth was in this period.

MHRD
NME-ICT
The Permian Period
The carboniferous period is followed by the last period of this
era called Permian period. It is spread between 286 Mya and
245 Mya. The significant observations of the Permian period
are:
World-wide continental uplift and orogenic movements.
Widespread aridity on one side and Glaciation at the other
side.
Extinction of Palezoic Plants and invertebrates (251 Mya).
Reduction in all types of life.
Almost 95% of life on the earth became extinct. (…Contd)

MHRD
NME-ICT
 The Primitive reptiles dominated in places.
 Extinction of all Trilobites, Graptolites and Blastoids,
were seen in this period.
 The Beetles and flies got evolved.
 Much marine life flourished in warm shallow reefs.
 There was an abundance of Spiriferid brachiopods,
bivalves, foraminifers and ammonoids.
The Permian Period
(…Contd)

MHRD
NME-ICT
 The Cone-bearing Gymnosperms (the first true seed
plants) and the first true mosses appeared.
 The landmasses united into the super continent
Pangaea, creating the Appalachians, in this period.
 This period records the end of Permo-Carboniferous
glaciations.
The Permian Period

MHRD
NME-ICT
Mesozoic Era
The duration of MESOZOIC ERA is the time of Middle life in
the history of the earth. This is the Age of reptiles. This era
has the span of time between 245 Mya and 66.4 Mya.
It is further divided into three periods as:
a)Cretaceous -144 - 66.4 Mya
b)Jurassic -208 - 144 Mya
c)Triassic -245 - 208 Mya.
This is the world’s fascinating era, with very unique life and
features.

MHRD
NME-ICT
The Triassic period is the first period of the Mesozoic era.
It is spread between 245 Mya and 208 Mya.
The significant observations of this period are:
Continent emergent Seas were marginal in this period.
The Climate was arid.
Occurrence of Terrestrial deposition happened during
this period.
The Triassic Period
(…Contd)

MHRD
NME-ICT
The Triassic Period
 Formation of Salt, Gypsum and red beds have been
observed.
 The dominance of Archosaurs on land as dinosaurs,
ichthyosaurs, nothosaurs in oceans and pterosaurs in the air.
 The apearance of Primitive Mammals was found in the
Triassic.
 The domination of Reptiles and Cycads, reduction of Marine
Invertebrates, first appearance of mammals and crocodilian
were the unique things.
(…Contd)

MHRD
NME-ICT
 Dicroidium flora were common on land.
 Extreme abundance of ceratitic ammonoids were seen.
 The modern Corals appeared.
 Orogenic Movements prevailed in some parts.
 The Pangaea was still in existence.
 Altering global climate and ocean circulation happened.
 The appearance of modern conifers, cycadeoids, first turtles,
lizards, mammals and dinosaurs, have been seen in this period.
The Triassic Period

MHRD
NME-ICT
 The world’s most famous period is the Jurassic period.
 The Dominance of Dinosaurs in Jurassic got registered
in every mind of the human life due to global media
coverage.
 It is spread between 208 Mya and 44 Mya.
The Jurassic Period
(…Contd)

MHRD
NME-ICT
 The significant observations of the Jurassic period are:
 Atmospheric CO2 levels 4-5 times more than the
present day levels (1200-1500 ppmv).
 Many types of Dinosaurs-Sauropods, Carnosaurs and
steepsaurs dominated.
 Great plant eating dinosaurs were in existance.
 Lush growth of ferns and palm-like cycads,
Gymnosperms also have grown much.
(…Contd)
The Jurassic Period

MHRD
NME-ICT
 Oceans were with full of fish, squids and coiled
ammonites.
 Appearance of the first frogs, salamanders, crocodiles,
flying reptiles and birds were noticed.
 The formation of oilfields of North Sea happened.
 The First birds and lizards appeared.
 Mammals were common.
(…Contd)
The Jurassic Period

MHRD
NME-ICT
 Bivalves, Belemnites and Ammonites were abundant.
 Sea urchins were common along with crinoids,
starfish, sponges, terebratulid, rhynchonellid
brachiopods.
 Breakup of Pangaea into Gondwana and Laurasia
happened during this period only.
The Jurassic Period

MHRD
NME-ICT
The cretaceous period is a notable period in geologic
history. It is spread between 144 and 66.4 Mya.
The significant observations of the Cretaceous period are:
This is the last period of the age of Dinosaurs.
First primates, angiosperms appeared.
World continent Pangaea begins.
Atmospheric Co2 close to present day levels.
The Cretaceous Period
(…Contd)

MHRD
NME-ICT
 Modern flowering plants proliferated along with new
types of insects.
 Ammonites, belemnites, bivalves, echinoids and sponges
were all common.
 Many new types of dinosaurs and crocodilians appeared
on land.
(…Contd)

MHRD
NME-ICT
 Modern sharks appeared in the sea.
 Primitive birds appeared (toothed birds and flying
reptiles).
 Breakup of Gondwana and beginning of Rocky
Mountains.
 Widespread epicontinental Seas.
 Extensive chalk deposits.
 Marine Pelecypods were very abundant.

MHRD
NME-ICT
 The duration of CENOZOIC ERA is the time of
recent life. This is the age of mammals.
 This era has the Span of time from 65 Mya ago to the
present day.
 It is further divided into two major eras as:
 Quaternary Era (Age of man) and
 Tertiary Era (Age of mammals).
Cenozoic Era

MHRD
NME-ICT
The Tertiary Era
The Tertiary era includes the periods:
Pliocene 05 - 02 Mya
Miocene 25 - 05 Mya
Oligocene 38 - 25 Mya
Eocene 55 - 38 Mya
Paleocene 65 - 55 Mya

MHRD
NME-ICT
The Quaternary Era
The Quaternary era includes the periods:
Holocene 10000 years to the present
Pleistocene 1.6-0.01 Mya

MHRD
NME-ICT
Paleocene Period (65-55 Mya):
 Climate was Tropical.
 The modern plants appeared.
 The mammals diversity into a number of primitive
lineages following the extinction of the dinosaurs.
Paleocene Period
(…Contd)

MHRD
NME-ICT
 The world has seen the first large mammals.
 There was the Alpine orogeny.
 The Himalayan orogeny was also observed
between 55 Mya. and 48 Mya.
Paleocene Period

MHRD
NME-ICT
Eocene Period (55-38 Mya):
 Sea was Marginal.
 There was extensive terrestrial sedimentation.
 Reglaciation in South Pole happened.
Eocene Period
(…Contd)

MHRD
NME-ICT
 The Dawn of mammalian dominance was seen.
 The Subordinate position for reptiles happened.
 Moderate, cooling climate was noticed.
 The Archaic mammals flourished.
 The primitive whales diversity was seen.
 The First grasses appeared.
Eocene Period

MHRD
NME-ICT
Oligocene Period (38-25 Mya):
 Warm but cooling climate prevailed on the earth.
 There was a rapid evolution and diversification of fauna
especially the mammals and modern flowering plants.
 The Early ancestral elephants appeared.
 The Carnivores and ungulates become well-established.
Oligocene Period

MHRD
NME-ICT
Miocene Period
Miocene Period (25-5 Mya):
 Moderate Icehouse climate.
 Extensive glaciation in Southern Hemisphere.
 Orogeny in Northern Hemisphere.
 Modern mammal and bird families become recognizable.
 Horses and Mastodons diverse.
 The first Apes appeared.
(…Contd)

MHRD
NME-ICT
 Whales, Apes and grazing mammals dominated.
 Widespread volcanism and basalt flows were seen.
 Notable advances in the horses and elephant families.
 Spread of grasslands as forests contracted.
Miocene Period

MHRD
NME-ICT
Pliocene Period (05-02 Mya):
 Worldwide elevation continues.
 Continental uplift and mountain building.
 The Ice Age began.
 The Seas were restricted.
Pliocene Period
(…Contd)

MHRD
NME-ICT
Pliocene Period
 The world has experienced Cool and dry climate.
 Many of the existing generation of mammals and recent
mollusks appear.
 Homo habilis appears. The Horses and Elephants became
almost modern in appearance.
 First known appearance of hominids (human like
primates).
 The large carnivores were dominated.

MHRD
NME-ICT
Pleistocene Period
Pleistocene Period (1.6-0.01 Mya):
 The Era of ice ages. Glacial climate.
 Four great ice advances and retreats.
 Fluorishing and then extinction of many large mammals.
 Evolution of modern humans was seen in this period.
(…Contd)

MHRD
NME-ICT
 The Dawn of human stone-age cultures.
 Volcanic eruptions destroy human populations.
 Cromagnon man – First appearance of present species.
 The Neanderthal man – Paleolithic culture started.
Pleistocene Period
(…Contd)

MHRD
NME-ICT
Pleistocene Period
 The Heidelberg man and Paleolithic culture started.
 The Formation of large scale Deserts – Sahara was
formed.
 There was planetary spread of Homosapiens over Eurasia.
 There was extinction of many species due to ice ages.
 There was an extinction of many large mammals and birds
due to humans.

MHRD
NME-ICT
Holocene Period (10000 years to the present)
 Rise of human civilization.
 Major habitat changes and deforestations caused by
Introduction of Pests and habitat destruction.
 The beginning of Agriculture happened in this period only.
 Humans built cities.
 Paleolithic and Nieolithic cultures began around 10000 BC.
Holocene Period
(…Contd)

MHRD
NME-ICT
The world has seen the following ages:
 Copper Age 3500 BC.
 Bronze Age 2500 BC.
 Iron Age (1200 BC).
 Man used iron implements in 1350 BC.
 Youthful landforms and high order relief features were
seen.
Holocene Period

MHRD
NME-ICT
 Time has been flowing since the beginning of the
earth. Time will continue to flow long after the
present generation also.
 To understand the past, we should know the present.
 To understand the present, we should know the past.
 The age of the earth is one important aspect in Earth
Science studies. Every period has to be studied in
detail.
Conclusion

MHRD
NME-ICT
Thank YouThank You

The Geological Time Scale

More Related Content

What's hot

Similar to The Geological Time Scale

More from Prof. A.Balasubramanian

Recently uploaded

The Geological Time Scale