Mass extinctions are periods in Earth's history when abnormally large numbers of species die out simultaneously or within a limited time frame

2. Mass Extinction - Definition
 A MASS EXTICTION IS A
GLOBAL DECREASE IN THE
AMOUNT OF LIFE.
 IT IS THE EXTINCTION OF A
NUMBER OF SPECIES IN A
RELATIVELY SHORT TIME

3. The 5 Major Mass Extinctions

4. Extinction
Ordovician-Silurian

5. End of Ordovician Mass Extinction – 443 Ma
70% of marine species became extinct
Main groups affected are Trilobites, Graptolites,
Echinoids, Brachiopods

6. Glaciations-Possible Causes
Supercontinent positioned
in high latitudes/close to the poles

7. Glaciations-Effects on Ecosystems
Loss of habitat as ice masses grow
Could eventually lead to ‘Snowball Earth’ scenario
Global cooling.

8. A small minority of scientist have suggested
that the initial extinction could have been
caused by a gamma ray blast originating from
a hyper nova within 6000 Lys from earth.
A Gamma ray blast are a flashes of gamma rays
associated with extremely energetic high speed
particles and radiation moving in space.
 A mere ten seconds of blast could have
destroyed earth’s ozone layer.

10. A series of events that lasted around 10 Ma
Cephalopods, Fish and Corals most affected

11. TERRESTRIAL PLANT
New root
system Decreased CO2
Boosted soil formation
Releasing nutrients into seas &
ocean
Algae boom
Anoxia
Chiller climate
Glaciation
TERRESTRIAL PLANT
New root
system Decreased CO2
Boosted soil formation
Releasing nutrients into seas &
ocean
Eutrophication
Anoxia

12. PERMIAN-TRIASSIC
EXTINCTION

13. The largest mass extinction event removing 95% of
marine species and 50% of marine families
Trilobites, Cephalopods, Bryozoans,
Corals, Crinoids badly affected
Major faunal and floral overturn on land
Marks the boundary between dominance
by the Palaeozoic and Modern Fauna

16. Methane Hydrates in Ocean Floor Sediments
Global warming may result
in deep ocean temperatures
rising and the release of
large volumes of methane
from ocean sediments
The rapid release of large
amounts of methane into
the atmosphere will result
in highly accelerated
global warming

18. End Triassic Mass Extinction – 200 Ma
Multiple event mostly affected the land
where over 95% floral species eliminated
Around 30% marine species became extinct – mainly
reef dwellers, Ceratites, Brachiopods and Bivalves

19. Pangea broke up and eventually splitting
America from Europe and Africa and forming
the Atlantic ocean.
The Central American Magmatic Province
had begun to erupt huge amount of basalt lava

20. Billions of tonnes of
carbon dioxide and
sulphur dioxide released
into the atmosphere
during eruptions
Both are powerful
greenhouse gases and
will contribute to very
rapid global warming

21. When it rains the sulphur dioxide will come
back down to Earth dissolved in rainwater and
the acid rain will kill vegetation on a large scale
CO2 will cause global warming.
Rise in sea level
Global anoxia.

23. CRETACEOUS–PALEOGENE
EXTINCTION

24. K-T Mass Extinction
Around 70% of all species wiped out
Dinosaurs, Reptiles, Ammonites, Belemnites,
Brachiopods, Bivalves, Foraminifera

25. A large asteroid or meteorite (10km in diameter)
collided with the Earth 65 million years ago

26. Evidence - Asteroid Impact Location
Location of possible impact site discovered on
the Yucatan Peninsula in Mexico at Chixulub
The impact structure is a circular
depression about 180 km in diameter

27. Evidence – The K-T Boundary Layer
The presence of a thin 2cm
layer of iridium-rich clay
found all over the world
within sedimentary rocks
The K-T Boundary Layer
dates the same everywhere
at 65.5 Ma +/- 0.3 Ma
Iridium is a transition
element, rare on Earth but
found in meteorites.
First proposed by Luis
Alvarez in 1980

28. Evidence – Wildfires & Fossil
The K-T Layer has high concentrations of carbon in many locations,
suggesting that the asteroid impact may have generated wildfires.

29. Evidence – Tsunami Deposits
It is thought that the asteroid
impact occurred in the sea and
initially produced a crater 100
km wide and 30 km deep
This would have displaced
vast volumes of seawater and
generated a series of very
large tsunamis possibly over
100 metres in height
The tsunamis would have
travelled great distances inland,
and in Texas at Waco there are
large-scale sedimentary deposits
thought to be of tsunami origin.

30. Evidence – Tsunami Deposits
The tsunami deposits in Waco, Texas are thought to be
from the waves generated by the K-T asteroid impact.
The sediments are estimated to have been deposited at
least 300km inland by the tsunamis!

31. Flood Basalt Eruptions 66 Ma – The Deccan Traps
Lasted over a period of 2 My .
Over 2000 metres thick and cover 500,000 km²
May have originally covered 1,500,000 km²
Released dust and sulphuric aerosols and blocking sunlight
thus reduced photosynthesis.
Also emitted CO2 .

33. Holocene Extinction
The Earth is currently losing about 30,000 species
of plants, animals and insects a year.
That is about 3 species every hour! Lost forever.
It will take millions of years to repair what we
destroy in just a few decades.

34. CAUSES
Rising CO2 levels
Habitat destruction
Invasive species
Pollution
Over harvesting

35. How You Can Help
 Turn lights and appliances off when not using
them.
 Use energy efficient light bulbs.
 Make space for wildlife. Build a birdhouse , plant a
tree, compost your wastes and don’t use harmful
chemicals in your home or garden.
 Recycle, Reduce and Reuse.

36. That’s All Folks!
THANK
YOU..!!!