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..!!!