The document discusses 5 major mass extinctions that have occurred in Earth's history. Mass extinctions refer to the extinction of a large number of species within a short period of time across the globe. The biggest mass extinction was the Permian-Triassic extinction about 252 million years ago, which killed off around 95% of all species. Causes of mass extinctions included climate change, asteroid impacts, volcanic eruptions, and changes in sea levels. The 6th mass extinction is currently underway due to human activity such as pollution, habitat destruction, and overexploitation of resources. Up to 50% of all species may go extinct by 2100 if human impacts are not addressed.

1. Mass Extinction
Dr. S. R. Jakhar
Department of Geology
Faculty of Science
Jai Narain Vyas University
Jodhpur

2. Mass extinction means the extinction of a
large number of species within a relatively
short period of geological time from entire
globe,
as between the Cretaceous and Tertiary
Periods when three-quarters of all
species on earth, including most
dinosaurs, became extinct.

3. According to Dough Erwin, Smithsonian Institution’s National Museum of
Natural History, there five worst mass extinctions occurred in Earth history:
1. Ordovician-Silurian extinction, about 439 m.y. ago.
2. Late Devonian, about 364 m.y. ago and
3. Permian-Triassic, about 215 m.y. ago
4. End of Triassic, roughly 199 to 214 m.y. ago
5. Cretaceous-Tertiary Extinction, 65 m.y ago
Sixth Massive Extinction in the history of life on the earth is pre-destined
on us to prove the principle of uniformitarianism

4. Hadean Eon 4600 – 3900 M.Y. Time lapse without leaving any evidences on the Earth Surface
Position of Mass Extinction in Geological Timescale

6. Causes of Mass Extinction
Throughout geological history mass extinctions have periodically occurred
primarily due to major modification of extensive regions and consequent
destruction of natural environments, such as
•Leveling effects of earth’s surface, Plate Tectonics
•Submergence of land under the sea,
• Emergence of land from the ocean (transgression and regression of the sea),
•Glaciations,
•Climatic changes to the extreme. Global warming, global cooling, methane eruptions
and anoxic events (when the earth's oceans lose their oxygen).
•Impact of cosmic bodies, like asteroids, comets, etc.
•Flood basalt events (volcano eruptions),
•Gamma Rays and
• Disease: Species-destroying-diseases induced by bacteria, fungi, and viruses
Living environmental and ecological changes, harmful to the survival of
certain life, especially animal and plant lives,.

7. The earliest mass extinction took place during
•1. Ordovician – Silurian, about 439 m.y. ago,
caused by by a short, severe ice age that lowered sea-levels,
glaciers forced and then by rising sea-levels, as glaciers
melted.
Uplift of the Appalachians (Mountain).
The newly exposed silicate rock sucked CO2 out of the atmosphere,
chilling the planet.
The life toll, possibly, had been 25% of marine families and
60% of marine genera.

8. The event took its hardest toll on marine organisms such as shelled
brachiopods, conodonts, Graptolites and the trilobites.
Brachiopod fossils from the
Ordovician period
Graptolites

9. The second mass extinction occurred during
2. Late Devonian, about 364 million years ago.
Little is known about land organisms at that time.
The late Palaeozoic, which lasted for about 165 million.
This period was characterized by vigorous climatic conditions over the
entire earth.
Intensive glaciations, mountain building, flood plains and extensive spread
of sea. ozone depletion, nitric acid formation, anoxia, fire, and destruction of
the food chain;
Such conditions were extremely unfavourable for living things and many
species were exterminated, especially among the marine animals
The likely culprit was the newly evolved land
plants that emerged, covering the planet
during the Devonian period. Their deep roots
stirred up the earth, releasing nutrients into
the ocean. This might have triggered algal
blooms which sucked oxygen out of the water,
suffocating bottom dwellers like the trilobites. Trilobites

10. •The earth witnessed its third mass extinction during
3. the Permian-Triassic, about 215 m.y. ago.
Known as “the great dying”, this was by far the worst extinction event
ever seen; it nearly ended life on Earth.
•A great number of animal species disappeared.
•Those affected were chiefly marine invertebrates. Land-life was not
sufficiently varied.
•Among the ancient lifes that were finally exterminated were trilobites
and eurypterids;
• Another group prolifically represented by productid brachiopods in the
Devonian, none has been found in Triassic (230-199 m.y.).
The Permian-Triassic catastrophe, about 215 m.y. ago, was Earth’s
worst mass extinction killing 95% of all species, 53% marine families,
84% of marine genera (witnessed extinction of trilobites and
brachiopods) an estimated 70% of land species, such as plants, insects,
and vertebrate animals.
Impact of a comet, or asteroid or flood – volcanism from the Siberian
traps and related loss of oxygen in the seas might have been the
causative factors.

11. Asteroid impact
The tabulate corals were lost in this period –
What caused it? A perfect storm of natural
catastrophes. A cataclysmic eruption near
Siberia blasted CO2 into the atmosphere.
Methanogenic bacteria responded by belching
out methane, a potent greenhouse gas.
Global temperatures surged while oceans
acidified and stagnated, belching poisonous
hydrogen sulfide.
Rocks after this period record no coal deposits.
tabulate corals
The shockwave from the
asteroid's landing on the Yucatán
Peninsula devastated the
immediate area.

12. 4. End of Triassic, roughly 199 to 214 m.y. ago,
•caused by massive floods of lava, erupting from the Central Atlantic
magmatic province – an event that triggered the opening of the Atlantic
ocean. The volcanism may have led to deadly global warming;
•22 percent of marine families, and 52 percent of marine genera
disappeared.
A jawless eel-like vertebrate
named the Conodont got
extinct
Conodonts

13. 5. Cretaceous-Tertiary Extinction, 65 m.y ago,
witnessed one of the most spectacular devastation of marine life and land
vertebrates, including the dianosaurs
The heaviest blows were dealt to the land-living vertebrates – the flying
reptiles or pterosaurs, the long-necked marine plesiosaurs, and two orders
and relatively specialized for certain modes of life.
Disappearance of dinosaurs. This group had dominated the earth for at least
140 m.y.
Many theories have been proposed to explain their extinction – rise of eggs-
eating reptiles, extremes of temperatures, world-wide lowering of
temperature, which were unfavourable; too-hot climate, higher temperatures
not favourable to the survival of sperms, cosmic or astronomical events, and
physiological changes within.
Of these various views, the slow changes in climate brought about by shifting
seas and land-masses may be sufficient to account for the demise of the
creatures.

14. Artist’s impression of a 6-mile-wide asteroid
striking the Earth.
Scientists now have fresh evidence that such a
cosmic impact ended the age of dinosaurs near
what is now the town of Chixculub in Mexico.
Extinct ammonites.
Today, the ammonites’ oldest
surviving relative is the
nautilus. Will it survive the sixth
great extinction?

15. Dianosaurs fossil eggs: Nagpur
Fossil of Dianosaurs

17. Sixth Mass extinction,
otherwise referred to as the Holocene extinction, or the Anthropocene extinction,
is a current event, and is one of the most significant extinction events in the history
of the Earth which is underway.
This ongoing extinction of species coincides with the
present Holocene epoch (approx. 11,700 years), and is a result of human activity.
This large number of extinctions spans numerous families of plants and animals,
including mammals, birds, amphibians, reptiles and arthropods.
With widespread degradation of highly biodiverse habitats such as coral
reefs and rainforests, as well as other areas, the vast majority of these extinctions
are thought to be undocumented, as no one is even aware of the existence of the
species before they go extinct.
The current rate of extinction of species is estimated at 100 to 1,000 times higher
than natural background rates.
By the year 2100, human activities such as pollution, land clearing, and
overfishing may drive more than half of the world's marine and land species
to extinction.

18. Don’t be so worried but take care of mother Earth with
consciousness
More than 90 percent of all organisms that have ever lived on Earth are
extinct.
As new species evolve to fit ever changing ecological niches, older species
fade away.
Though these mass extinctions are deadly events, but they open up the
planet for new life-forms to emerge.
Dinosaurs appeared after one of the biggest mass extinction events on
Earth, the Permian-Triassic extinction about 250 million years ago.
The most studied mass extinction, between the Cretaceous and Paleogene
periods about 65 million years ago, killed off the dinosaurs and made room
for mammals to rapidly diversify and evolve.

19. START ACTING ON UNDER MENTIONED POINTS TO SLOW DOWN
THE EXTINCTION RATE OF ON SET SIXTH MASS EXTINCTION
•Take care of pollution free Air, water, soil and sound.
•No use of pesticides and chemical manure for agriculture Crops
•Generate all power from solar cells
•Make mother earth more green through plantation

20. Thank you