Geological time scale.

#Frist PPT ON GEOLOGICAL TIME SCALE.

2. 4.7 billion history of the earth from its origin to the present
The Geological time scale is a record of the life forms and
geological events in Earth’s history.
The influence of geological and climatic changes on the life and the
evolution of the living organism had been well analyzed.
Scientists developed the time scale by studying rock layers and
fossils world wide.
Radioactive dating helped determine the absolute divisions in the
time scale.

3. GTS: The geologic time scale (GTS) is a system of chronological dating that relates geological strata
(Stratigraphy) to time, and is used by geologists, paleontologists, and other Earth scientists to describe the
timing and relationships of events that have occurred during Earth's history. The tables of geologic time
spans, presented here, agree with the nomenclature, dates and standard color codes set forth by the
International Commission on Stratigraphy (ICS)

4. Nicholas Steno laid down the principles underlying geologic time scales in the late seventeenth century.
Steno argued that rock layers (strata) are laid down in succession, and that each represents a “slice”
of time. He also formulated the principle of superposition, which states that any given stratum is
probably older than those above it and younger than those below it. Steno's principles were simple, but
applying them to real rocks proved complex. During the eighteenth century, geologists came to realize
that:
1) Sequences of strata were often eroded, distorted, tilted, or even inverted after deposition.
2) Strata laid down at the same time in different areas could have entirely different appearances.
3) The strata of any given area represented only part of the Earth's long history.
The first serious attempts to formulate a geological time scale that could be applied anywhere on Earth
took place in the late eighteenth century. The most influential of those early attempts (championed by
Abraham Werner, among others) divided the rocks of the Earth's crust into four types: primary,
secondary, tertiary, and quaternary. Each type of rock, according to the theory, formed during a
specific period in Earth history. It was thus possible to speak of a "Tertiary Period" as well as of
"Tertiary Rocks." Indeed, "Tertiary" and "Quaternary" remained in use as names of geological periods
well into the twentieth century.

5. The identification of strata by the fossils they contained, pioneered by William Smith, Georges Cuvier, and
Alexandre Brogniart in the early nineteenth century, enabled geologists to divide Earth history more
finely and precisely. It also enabled them to correlate strata across national (or even continental)
boundaries. If two strata (however distant in space or different in composition) contained the same
fossils, chances were good that they had been laid down at the same time. Detailed studies of the strata
and fossils of Europe produced between 1820 and 1850 formed the sequence of geological periods still
used today.
When William Smith and Sir Charles Lyell first recognized that rock strata represented successive time
periods, there was no way to determine what time scale they represented. Young earth creationists
proposed dates of only a few thousand years, while others suggested large (and even infinite) ages. For
over one hundred years, the age of the Earth and of the rock strata was the subject of considerable
debate until advances in the latter part of the twentieth century allowed radioactive dating to provide
relatively firm dates to geologic horizons. In the intervening century and a half, geologists and
paleontologists constructed time scales based solely on the relative positions of different strata and
fossils
In 1977, the Global Commission on Stratigraphy (now the International Commission) started an effort to
define global references (Global Boundary Stereotype Section and Points) for geologic periods and
faunal stages. Their most recent work is described in the 2004 geologic time scale of Gradstein, Ogg,
and Smith (2005), and used as the foundation of the table on this page. The tables of geologic periods
presented here are in accordance with the dates and nomenclature proposed by the International
Commission on Stratigraphy, and uses the standard color codes of the United States Geological Survey

6. QUESTIONS. ANSWERS.
1=> what is mean by Strata?

8=> What is mean by Radioactive
dating?

9=>What is mean by Stratigraphy.



1=> In geology and related fields,
a stratum (plural: strata) is a layer
of Sedimentary rock or soil, or igneous
rock that were formed at the Earth's surface.
8=> Radiometric dating or radioactive dating is a
technique used to date materials such as
rocks or carbon, in which trace radioactive
impurities were selectively incorporated
when they were formed.
9=> Stratigraphy is a branch of geology concerned
with the study of rock layers (strata) and
layering (stratification). It is primarily used in
the study of sedimentary and layer of
volcanic rock.

7. Who Was Nicolas Steno?
Nicolas Steno: (11 January 1638 – 5 December 1686) was a Danish scientist, a pioneer in
both anatomy and geology who became a Catholic bishop in his later years. Steno was
trained in the classical texts on science; however, by 1659 he seriously questioned
accepted knowledge of the natural world.

Importantly he questioned explanations for tear
production, the idea that fossils grew in the ground and explanations of rock formation.
His investigations and his subsequent conclusions on fossils and rock formation have led
scholars to consider him one of the founders of modern Stratigraphy and modern
geology.

8. Who Was Abraham Werner
Abraham Gottlob Werner (25 September 1749 – 30 June 1817) was a
German geologist who set out an early theory about the stratification of the Earth's
crust and propounded a history of the Earth that came to be known as Neptunium. While
most tenets of Neptunium were eventually set aside, Werner is remembered for his
demonstration of chronological succession in rocks; for the zeal with which he infused his
pupils; and for the impulse he thereby gave to the study of geology. He has been called the
"father of German geology

9. Who Was William Smith?
William 'Strata' Smith (23 March 1769 – 28 August 1839) was an English geologist,
credited with creating the first nationwide geological map.

At the time his map was first
published he was overlooked by the scientific community; his relatively humble education
and family connections prevented him from mixing easily in learned society. Financially
ruined, Smith spent time in debtors' prison. It was only late in his life that Smith received
recognition for his accomplishments, and became known as the "Father of
English Geology".

10. Who Was Georgas Cuvier?
Georges Cuvier, (23 August 1769 – 13 May 1832) was a French naturalist and zoologist,
sometimes referred to as the "founding father of paleontology".

Cuvier was a major
figure in natural sciences research in the early 19th century and was instrumental in
establishing the fields of comparative anatomy and paleontology through his work in
comparing living animals with fossils.

11. Who Was Alexandre
Brogniart?
Alexandre Brogniart (5 February 1770 – 7 October 1847) was a French
chemist, mineralogist, and zoologist, who collaborated with Georges Cuvier on a study of
the geology of the region around Paris

12. Who Was Sir Charles Lyell?
Sir Charles Lyell, (14 November 1797 – 22 February 1875) was a Scottish geologist who
popularized the revolutionary work of James Hutton. He is best known as the author
of Principles
of Geology, which presented uniformitarian's the idea that the Earth was
shaped by the same scientific processes still in operation today–to the broad general
public. Principles
of Geology also challenged theories popularized by Georges Cuvier,
which were the most accepted and circulated ideas about geology in Europe at the time.

13. Geologists have divided Earth's history into a series of time intervals. These time intervals are not equal
in length like the hours in a day. Instead the time intervals are variable in length. This is because geologic
time is divided using significant events in the history of the Earth.
Eons: Eons are the largest intervals of geologic time and are hundreds of millions of years in duration. In
the time scale below you can see the Phanerozoic Eon is the most recent eon and began more than 500
million years ago.
 Eras: Eons are divided into smaller time intervals known as eras. In the time scale below you can see
that the Phanerozoic is divided into three eras: Cenozoic, Mesozoic and Paleozoic. Very significant events
in Earth's history are used to determine the boundaries of the eras.
Periods: Eras are subdivided into periods. The events that bound the periods are widespread in their
extent but are not as significant as those which bound the eras. In the time scale below you can see that
the Paleozoic is subdivided into the Permian, Pennsylvanian, Mississippian, Devonian, Silurian, Ordovician
and Cambrian periods.
 Epochs: Finer subdivisions of time are possible, and the periods of the Cenozoic are frequently
subdivided into epochs. Subdivision of periods into epochs can be done only for the most recent portion
of the geologic time scale. This is because older rocks have been buried deeply, intensely deformed and
severely modified by long-term earth processes. As a result, the history contained within these rocks
cannot be as clearly interpreted.

16. The most largest division of time is EONS.
There are two types of Eons .
First Cryptozoic (Precambrian) eon This Eon Is Also Called Super Eon .
Second Phanerozoic eon .
These both Eons are further classified in to three eras.
Cryptozoic(Precambrian) Eon Expense Of Time = Proterozoic Era , Archaean, Hadean are in
order of increasing age.
 Cryptozoic (Precambrian)Eon Covers 88% of Earths History
Phanerozoic Eon Is the Eon of the visible light = Cenozoic (Recent Life), Mesozoic (Middle Life),
Paleozoic Era( Ancient Life).
Note:
Each Eon Is Further Divided Into Era.
Each Era Is Further Divided Into Periods.
Each Period Is Divided Into Epochs.
Each Epoch Is Further Divided Into Ages.

19. During The Precambrian Eon The earth was mostly water with
some small volcanic island.
Lasted from 540 million years ago to 4600 million years ago.
Oldest and longest (covers almost 88% or 90% of earth’s
history).
Simple organisms- bacteria, algae, protozoa was born.
Oldest rocks that we know were found in this eon which dates to
about 3.5 billion years old.
Divided into Three eras: Proterozoic, Archaean and Hadean era.

20.  This is the "hidden" portion of geologic time as there is little
evidence of this time remaining in Earth's rocks.
It Began with the formation Of the Earth 4.6 billion years ago and
ended 3.8.
4.6 BYA Formation of Earth and Moon
As indicated by dating of meteorites and rocks from the Moon.
4 BYA Likely origin of life
Indirect photosynthetic evidence of primordial life.
Evidence of materials created by organic decay.

21. During the Archaean, the Earth's crust had cooled enough to allow the
formation of continents and life started to form.
3.8 to 2.5 billion years ago
The eon of first life
3.8 BYA Oldest known rocks
3.5 BYA Oldest known fossils (single celled organisms resembling
bacteria)
Prokaryotes were the Earth’s sole inhabitants.
Evidence of stromatolites created by colonial cyanobacteria .
Earliest types of photosynthesis did not produce oxygen.
Oxygenic photosynthesis probably evolved in cyanobacteria.

22. The Younger Eon Is Proterozoic Era.
2.5 Billion to 570 Million years ago
The eon of the first multi-celled life
Emergence of protists, green algae and ediacaran biota
Evidence of oxygen producing bacteria begin to change the
atmosphere
Life turned from anaerobic to aerobic
Simple algae, protozoans, poriferans, annelids (End of the Pre-
Cambrian a period at least five times longer than all the geologic
time that follows.)

24. It Began from 540 million years ago and is still continuing today.
Divided into three Eras: First Paleozoic era (Past life) Second
Mesozoic era (Middle life) Third Cenozoic era (Present life).
It began with the Cambrian Period when diverse hard-shelled
animals first appeared. Its name was derived from the Ancient
Greek words (phanerós) and (zōḗ), meaning visible life, since it
was once believed that life began in the Cambrian, the
first period of this eon. The term "Phanerozoic" was coined in
1930 by the American geologist George Halcott Chadwick (1876–
1953). The time before the Phanerozoic, called the Precambrian,
is now divided into the Hadean, Archaean and Proterozoic eons.

25. It began 540 million years ago and ended 250 million years ago.
It is divided into 6 periods (Permian, Carboniferous period,
Devonian, Silurian, Ordovician, Cambrian).
 For the first time on Earth, organisms had hard parts (shells,
exoskeletons).
Evolution and development of pteridophytes, amphibians, reptiles,
fishes, wing bearing insects, trilobites etc.

26. It began 540 Mya And End In 485 Mya.
Cambrian Explosion: age of marine inverts.
Cambrian: among plants thallophytes were well established.
They diversified into various groups (Chlorophyceae,
Rhodophyceae etc.,).
Among anima is the aquatic arthropods and echinoderms came
to prominence.
End of the Cambrian denoted by the appearance of fish.
The Cambrian is divided into four epochs (series) and
ten ages (stages)

27. It Began 485 Mya and End in 440 Mya
Green plants (Bryophytes) and fungi first appeared on land.
Formation of coral rocks and mollusks and echinoderms.
First vertebrate: Jawless fishes,
Among arthropods, the trilobites were more prominent during
this period.
The origin of early vertebrate: major event in the evolution of
animals.

28. It Began 440 Mya and End in 415 Mya.
The oldest land plant conducting tissue (vascular plants)
originated and colonized the land.
Brachiopods and mollusks flourished.
The corals diversified.
Jawed fishes originated (scales and paired fins developed)
Origin of paired fins and jaws: major events in chordate
evolution.

29. It began in 415 Mya and End in 360 Mya.
Land living plants have become more successful.
The forests were filled with varieties of ferns and cycads (non-
flowering plants).
Among aquatic animals fishes became dominant.
The forefathers of almost all modern fishes lived (Age of fishes)
the sharks.
First aquatic/marine amphibians probably emerged Kellwasser
Extinction and the Hangenberg Extinction Event 19% of all families
5% of all genera went extinct.

30. It lasted from 360 million years to 300 Million years.
It is an important period of Paleozoic era.
During this period, first reptiles and pteridophytes were formed and coal
plants got spread
The dead bodies got buried in this period forming the coals that we use today.
Massive upraising of land : formation mountain ranges.
Huge water bodies were broken into smaller lakes: cause the origin of lungs
(to live temporarily on land) in fishes.
Encouraged the origin of the amphibians very first land vertebrates (tetra
pods).
The origin of land living amphibians were further increased by the
proliferation of several land living insects.
 Giant arthropods populate the land.
Collectively known as Carboniferous (carbon bearing) period.
Due to geotectonic changes : several forests got buried under the soil.

31. It lied between 300 million years to 250 million years.
It is also an important period of Paleozoic era. Largest mass
extinction happened in this period.
Scientists are not sure what caused this mass extinction (maybe
climate change & volcanoes).
90% of ocean life and 78% of land life died.
Represented by early cone bearing gymnosperms and mosses.
Beetles and flies already appeared.
Some amphibians dramatically laid land eggs (cleidoic eggs).

32. The Mesozoic ranges from 250 million to 66 million years ago. Also known
as "the Age of the dinosaurs“
The Mesozoic features the rise of reptiles on their 150 million year
conquest of the Earth on the land, in the seas, and in the air.
There are three periods in the Mesozoic Era: Triassic, Jurassic, and
Cretaceous.

33. It began in 250 Mya and End in 200 Mya.
Archosaur- protodinosaur .
First fossils of turtles, crocodiles, and dinosaurs obtained .
Fossil evidences : aquatic and flying reptiles thrived.
The mammals originated from reptiles.
Fourth major mass extinction: 23% of all the families and 48% of
all the genera went extinct.

34. Jurassic is an important period of Mesozoic era.
 It lasted from 200 million years ago to 145 million years ago.
During this period, first birds and mammals were formed.
Gymnosperms were dominating plants. The dinosaurs were
formed in Triassic period reached at their peak in this period.

35. It is a period of Mesozoic era which lasted from 145 million years
ago to 65.5 million years ago.
It marked the end of the Mesozoic Era and the beginning of the
Cenozoic Era.
All of the dinosaurs and half of the other animals & plants went
extinct in this period.
Scientists think an asteroid hit Earth, the dust clouds blocked out
the sun.
As a result, plants died, then herbivores, then carnivores.

36. It began in 65.4 Mya and Still Continues (Present).
Plenty of fossils (all modern animals and plants)
Subdivided into Tertiary (Paleogene & Neogene) and Quaternary
periods.
Further this era contains seven epochs.
Fossils: The origin and evolution of independent groups of animals
and man.

37. Paleocene Epoch: It began in 65 Mya and End in 54 Mya.
Social insects achieve ecological dominance.
Appearance of placental mammals (marsupials, insectivores, creodonts)
Eocene Epoch: It began in 54 Mya and End in 38 Mya.
Ungulates originated.
The ancestral form of modern horses lived.
The Azolla Event- freshwater fern blooms die at the bottom of Arctic Sea,
drawing down large amounts of CO2 (reduced by 80%) and triggering an ice
age.
Oligocene epoch: It began in 38 Mya and End In 26 Mya.
Several animals with ancient characteristics became extinct.
Mammals continue to diversify.
Modern mammalian families established.
Apes originated.

38. Miocene epoch: It began in 26 Mya and End in 7 Mya.
Several varieties of grasses evolved in Europe and N. America
(large prairies formed).
These changes encouraged the evolution of fast running
herbivorous mammals and their predators.
Pliocene Epoch: It began in 7 Mya and End in 2 Mya.
Prairie's enlarged still further in several regions.
Rodents became more successful.
Mammals increased in number.
Appearance of Australopithecus, genus of hominids.

39. Pleistocene epoch: It began in 2 Mya and End in 1 Mya.
Several glaciations happened.
popularly called the ‘modern Ice age’.
Homo habilis appeared.
Homo erectus first moves out of Africa.
The evolution of horses and man reached the final stages.
Homo sapiens appeared.
Today we are living in an inter-glacial Period.

41. It Began in 1 Mya And Still Continues.
Development of agriculture.
Domestication of animals.
250 Years ago: Start of the Industrial Revolution.
50 Years ago: Space travel Humans walk on the surface of the
moon (1969).
Animal cloning (Dolly the sheep).
Animal and Plant hybridization.
Improved communication.
Health care development.
Biotechnology.