MASS EXTINCTION
MASS EXTINCTION
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
The 5 Major Mass Extinctions
Extinction
Ordovician-Silurian
End of Ordovician Mass Extinction – 443 Ma70% of marine species became extinct
Main groups affected are Trilobites, Graptolites, Echinoids, Brachiopods
Glaciations-Possible Causes
Supercontinent positioned in high latitudes/close to the poles
Glaciations-Effects on Ecosystems
Loss of habitat as ice masses growCould eventually lead to ‘Snowball Earth’ scenario
Global cooling.
G A M M A R A Y B L A S TA 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.
ExtinctionLate Devonian
Late Devonian Mass Extinction – 375 Ma A series of events that lasted around 10 Ma
Cephalopods, Fish and Corals most affected
Late Devonian Mass Extinction – 375 Ma
TERRESTRIAL PLANT
New root system Decreased
CO2Boosted soil formation
Releasing nutrients into seas & ocean
Algae boom
Anoxia
Chiller climate
Glaciation
TERRESTRIAL PLANT
New root system Decreased
CO2Boosted soil formation
Releasing nutrients into seas & ocean
Eutrophication
Anoxia
PERMIAN-TRIASSIC
EXTINCTION
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
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
Triassic - Jurrasic Extinction
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
Flood Basalt Eruptions
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
Flood Basalt Eruptions
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
Flood Basalt Eruptions
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 levelGlobal anoxia.
CRETACEOUS –PALEOGENE
EXTINCTION
K-T Mass Extinction
Around 70% of all species wiped outDinosaurs, Reptiles, Ammonites, Belemnites,
Brachiopods, Bivalves, Foraminifera
A large asteroid or meteorite (10km in diameter) collided with the Earth 65 million years ago
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
Evidence – The K-T Boundary LayerThe 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
Evidence – Wildfires & Fossil
The K-T Layer has high concentrations of carbon in many locations,suggesting that the asteroid impact may have generated wildfires.
Evidence – Tsunami DepositsIt 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.
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!
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 km²Released dust and sulphuric aerosols and blocking sunlight
thus reduced photosynthesis.Also emitted CO2 .
HOLOCENE EXTINCTION
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.
CAUSES
Rising CO2 levelsHabitat destructionInvasive speciesPollutionOver harvesting
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.
That’s All Folks!
THANK YOU..!!!