Five major mass extinction

2. TIMELINE FOR MASS EXTINCTION
MILLIONS OF YEARS AGO
 Ordovician –Silurian Extinction Event -445mya
 Late Devonian Extinction Event – 358mya
 Permian Triassic Extinction Event -251mya
 End Triassic Extinction Event -201mya
 Cretaceous-Tertiary Extinction Event -66mya

3. “
”
MASS EXTINCTION
 An extinction event ( also known as a mass extinction or biotic
crisis ) is a widespread and rapid decrease in the amount of life
on earth.
 Extinction occurs at an uneven rate.
 Marine fossils are mostly used to measure extinction rate
because of their superior fossil record and stratigraphic range
compared to land organisms.
 Extinction events are relatively short (in terms of geological
time) periods with greatly increased extinction rate.
 A mass extinction event must eliminate >60% of species in a
relatively short period of geological time with widespread
geographical and taxonomical impacts.

4. WHAT CAUSES MASS EXTINCTION ?
The best known cause of a mass
extinction is the asteroid impact that
killed off the non-avian dinosaurs.
Volcanic activity is implicated in at least
three mass extinctions .
It is true that multiple causes may have
contributed to many mass extinctions, but
they have some things in common; they
cause major changes in Earth system – It’s
ecology , atmosphere , surface, and waters
– at rapid rates.

6. The Ordovician Mass Extinction
When:
The Ordovician Period of the Paleozoic Era (about
445-450 million years ago)
Size of the Extinction:
Up to 85% of all living species eliminated
Who became extinct?
All of the major animal groups of the Ordovician
oceans survived, including trilobites, brachiopods,
corals, crinoids and graptolites, but each lost
important members. Widespread families of
graptolites came close to total extinction.
Suspected Cause or Causes:
 Intense Ice Age
 Falling Sea Level

8. THE DEVONIAN MASS EXTINCTION
When:-
The Devonian period of the Paleozoic era (about 358
million years ago)
Size of the extinction:
Nearly 80% of all living species eliminated
Who became extinct?
Most pronounced in tropical environments, particularly in
the coral reefs of the shallow seas.
Stromatoporoids finally disappeared in the end of the
Devonian.
Suspected cause or causes:
Anoxia.
Global cycle
Volcanic eruptions and/or meteor strikes

9. When:
The Permian Period of the Paleozoic Era (about 251
million years ago)
Size of the Extinction:
An estimated 96% of all living species eliminated
Who became extinct?
 Important groups of marine animals
disappeared at the end-Permian extinctions.
 Trilobites, which had lived in the oceans for
more than 250 million years, were lost.
Suspected Cause or Causes:
 Asteroid Impact,
 Sibarian volcanic Activity,
 Climate Change
 Anoxia
THE PERMIAN MASS EXTINCTION- “MOTHER MASS EXTINCTION”

11. The Triassic-Jurassic Mass Extinction
When:
The end of the Triassic Period of the Mesozoic Era
(about 201 million years ago)
Size of the Extinction:
More than half of all living species eliminated
Who became extinct?
 Brachiopods, shelled cephalopods, sponge
and corals were particularly hard hit.
 On land, casualties included the phytosaurs,
a group of crocodile-like animals.
Suspected Cause or Causes:
 Major volcanic activity with basalt flooding
 Global climate change
 Changing pH and sea levels of the oceans

12. The Cretaceous-Tertiary mass extinction
When:
The end of the Cretaceous Period of the Mesozoic Era
(about 66 million years ago)
Size of the Extinction:
Nearly 75% of all living species eliminated.
Who became extinct?
 the non-avian dinosaurs.
 Important marine invertebrates such as
ammonites, cephalopods
 Some bivalves, such as the reef-building rudists
and some relatives of modern oysters.
Suspected Cause or Causes:
 Extreme asteroid or meteor impact
 Deccan volcanism

13. EVIDENCE – ASTEROID IMPACT LOCATION
EVIDENCE of K-T MASS EXTINCTION -
FLOOD BASALT ERRUPTION 66mya –
THE DECCAN TRAPS
Location of possible impact site discovered on the
YUCUTUN Peninsula in MEXICO at CHIXULUB.
The impact structure is a circular depression about
180 km in diameter.
Erupted mainly over a period of 30,000 year
over 2000 meters thick and cover 500,000
sq.km may have originally covered
1,500,000 sq.km caused a global drop in
temperature of 2degree Celsius.

14. Evolutionary Importance of Mass Extinction
Mass extinctions have sometimes accelerated the evolution of life on earth.
When dominance of particular ecological niches passes from one group of
organism to another , it is rarely because the new dominant group is “Superior” to
the old and usually because an extinction event eliminates the old dominant
group and makes way for the new one.
For example , mammals have been around for more than 200 million years -
but for most of the time , they have remained a small group of rodent – like
organism . It was only when the non-avian dinosaurs went extinct 65 million years
ago in the end –Cretaceous mass extinction , that mammals really diversified. In
less than 20 million years , they evolved into the great variety of mammals we
know today.

15. Earth Facing sixth Mass Extinction ?
The Sixth mass extinction is in progress , now with
animals going extinct 100 to 1000 times faster than at
the normal background extinction rate , which is
about 10 to 25 Species per year.
Many Researchers claim that we are in the middle of mass extinction event faster than the
Cretaceous-Tertiary extinction which wiped out the dinosaurs.
Possible causes are:-
 Habitat destruction including human-induced
climate change
 Human overpopulation
 Pollution

16. Reference: -
Earth System History –Steven M. Stanley
http;//en.Wikipedia.org/wiki/Extinction event.
http;//www.stratigraphy.org
http://www.nationalgeographic.com
As Our Scientists Predicted for Another Mass
Extinction where we all be the affected Species , So
we definitely have some responsibilities to find a
way to overcome or avoid this situation otherwise ,
the vast knowledge and intelligence will be GOOD
FOR NOTHING.
THANK
YOU