LATE ORDOVICIAN MASS EXTINCTION

• Recently, a paper published in the international journal Nature Geoscience has come up with a new reason behind the first mass extinction, also known as the Late Ordovician mass extinction.
• It 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.

Important points:

• A mass extinction event is when species vanish much faster than they are replaced.
• This is usually defined as about 75% of the world’s species being lost in a ‘short’ amount of geological time – less than 2.8 million years.
• The Ordovician mass extinction that occurred about 445 million years ago killed about 85% of all species.
• The Devonian mass extinction (about 375 million years ago) wiped out about 75% of the world’s species.
• The Permian mass extinction (about 250 million years ago) also known as the Great Dying caused the extinction of over 95% of all species.
• The Triassic mass extinction (about 200 million years ago) eliminated about 80% of Earth’s species, including some dinosaurs.
• This Cretaceous mass extinction (about 65 million years ago) is known for wiping out non-avian dinosaurs.

Latest Findings:

• There have been several theories behind each mass extinction and with advances in new technologies, researchers have been uncovering more intricate details about these events.
• For decades, the prevailing school of thought was that volcanism-induced global warming causes the oceans to lose oxygen and thus impact marine habitability, potentially destabilising the entire ecosystem.
• In recent years, mounting evidence points to several episodes in the Earth’s history when oxygen levels also dropped in cooling climates.
• Ordovician climate and marine biogeochemical cycles during that period showed “seafloor and upper-ocean oxygenation in response to ongoing global cooling.”
• This led to deep-sea anoxia affecting ocean circulation.
• Thus, the paper concludes that climate cooling may have led to changes in nutrient cycling, primary producer communities which ultimately drove the Late Ordovician mass extinction.

SOURCE: THE HINDU,THE ECONOMIC TIMES,MINT