Mass Extinctions

Mass Extinctions• Widespread and rapid decrease in the amount

of life in the Earth• Occurs when the rate of extinction is increased

with the respect to the rate of speciation

Great Oxygenation Event• Also called as Oxygen Catastrophe• 2.3 Billion years ago• Biologically induced appearance of dioxygen

in Earth’s atmosphere• Kills anaerobic organisms• First major mass extinction that happened in

history

End-Ediacaran Extinction• 542 Million Years Ago• Mass extinction of Acritarchs• Disappearance of Ediacaran Biota, most

common organisms living in the Ediacaran period

Ordovician-Silurian Extinction• 450-439 Million Years Ago• Second largest mass extinction in Earth’s

history• Dropping of sea level due to the formation of

glaciers• 49% of marine genera went extinct

Late Devonian Extinction• 375-360 Million Years Ago• Caused by widespread anoxia in ocean waters

or global cooling• 50% of all genera went extinct• Marine organisms were affected

Permian-Triassic Extinction• Great Dying• 252 Million Years Ago• Worst mass extinction in Earth’s history• 96% of all marine species went extinct and

70% of all terrestrial species went extinct• Caused by volcanism, asteroid impact or

breaking-up of the supercontinent Pangaea

Triassic-Jurassic Extinction• Late Triassic Extinction• 201.3 Million Years Ago• 34% of all marine genera went extinct• Crocodylomorphs and other land species also

went extinct• Caused by global climate change, asteroid

impact or volcanism

Triassic-Jurassic Extinction

Central Atlantic Magmatic Province

Cretaceous-Tertiary Extinction• K-T Mass Extinction• 65 Million Years Ago• 75% of all land and marine species went

extinct• Famously for killing the dinosaurs• Asteroid impact and volcanism

Cretaceous-Tertiary Extinction

Cretaceous-Tertiary Extinction