Mass Extinction By Joe Baraona

What is Mass Extinction? “The extinction of a large number of species within a relatively short period of geological time, thought to be due to factors such as a catastrophic global event or widespread environmental change that occurs too rapidly for most species to adapt.”

Five Major Mass Extinctions in History Ordovician–Silurian Extinction Event ~440 Million Years Ago Late Devonian Extinction Event ~ 370 Million Years Ago Permian–Triassic Extinction Event ~ 250 Million Years Ago Triassic–Jurassic Extinction Event ~ 205 Million Years Ago Cretaceous–Tertiary Extinction Event ~ 65 Million Years Ago

Five Major Mass Extinctions in History

Ordovician–Silurian Extinction Event Occurred Million Years Ago ~50% of all Marine Species Died Main Species Effected: Brachiopods, Bryozoans, Trilobite, Conodont and Graptolite families. Mainly Caused By Sharp Increase In Extinctions Possible Causes: Elongated Ice Age, Gamma Ray Bursts, Volcanism and Weathering

Late Devonian Extinction Event Occurred 370 million years ago Overall, 19% of all families and 50% of all genera went extinct. Affected primarily marine life Reef building organisms almost completely destroyed Primary cause: Ocean anoxia Possible Causes for Anoxia: Global cooling, oceanic volcanism, meteor impact Extinction caused by speciation rather than extinctions

Permian–Triassic Extinction Event Occurred Million Years Ago Earths most severe extinction “The Great Extinction” 96% of marine species, 70% of terrestrial vertebrate and 83% of all genera die Possible causes of extinction: climate change, impact events, anoxia, volcanism and methane hydrates in the ocean

Triassic–Jurassic Extinction Event Occurred 205 Million Years Ago Affected 20% of all marine families, therapsids and large reptiles At least ½ of all living species died during this time Allowed for the domination of dinosaurs Possible causes for extinction: gradual climate change, asteroid impact and volcanism

Cretaceous–Tertiary Extinction Event Occurred 65.5 million years ago Cause of the extinction of all non avian dinosaurs Allowed for the expansion of birds and mammals Possible reasons for extinction: volcanism or an impact event On March 4, 2010, a panel of 41 scientists agreed that the Chicxulub asteroid impact triggered the mass extinction

Opera - [YouTube - How many asteroids hit Earth?- What Really Killed the Dinosaurs? BBc Documentary] Asteroid Theory Video

-Comet Impact Image -Mass Extinction definition -Ordovician- Silurian Extinction -Devonian Extinction -Permian Triassic Extinction -Triassic Jurassic Extinction -Cretaceous Tertiary Extinction -Graph -Impact Image -Mexico Citations