Context

A recently published paper has come up with a ‘new reason’ behind the first mass extinction, also known as the Late Ordovician mass extinction.

About

What’s the new finding?

• The article notes that the cooling climate likely changed the ocean circulation pattern.
• This caused a disruption in the flow of oxygen-rich water from the shallow seas to deeper oceans, leading to a mass extinction of marine creatures.

What is mass extinction?

• Mass extinctions are defined as any substantial increase in the amount of extinction (lineage termination) suffered by more than one geographically wide-spread higher taxon during a relatively short interval of geologic time, resulting in an at least temporary decline in their standing diversity.

Major mass extinction events in the geological history of Earth:

• Ordovician-Silurian extinction 485 to 444 million years ago: killed about 85% of all species. 
• Late Devonian extinction - 383-359 million years ago: wiped out about 75% of the world’s species.
• Permian-Triassic extinction - 252 million years ago: also known as the Great Dying caused the extinction of over 95% of all species.
• Triassic-Jurassic extinction - 201 million years ago: eliminated about 80% of Earth’s species, including some dinosaurs.
• Cretaceous-Paleogene extinction - 66 million years ago

What’s leading to the extinction?

• destruction and fragmentation of habitats
• direct exploitation like fishing and hunting
• chemical pollution
• invasive species
• human-caused global warming
• Uncontrolled human population
• Overexploitation of resources