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Great Dying

The “Great Dying,” also known as the Permian-Triassic Extinction Event, is the most catastrophic mass extinction in Earth’s history. It occurred around 252 million years ago, marking the boundary between the Permian and Triassic periods, and the end of the Paleozoic and beginning of the Mesozoic Eras. This event completely reshaped the planet’s ecosystems and leaving a lasting impact on Earth’s history.

Causes and Triggers

Several factors likely contributed to the Great Dying, including volcanic activity, climate change, and oceanic disruptions. The Siberian Traps, a massive volcanic province, erupted over an extended period.

The eruption of the Siberian Traps had significant global consequences. The release of greenhouse gases, particularly carbon dioxide and methane, led to a rapid increase in global temperatures. This warming disrupted ecosystems and climate patterns, causing extreme weather events and shifts in ocean circulation.

The volcanic activity also released sulfur dioxide, which reacted with water vapor to form sulfuric acid, leading to acid rain. Additionally, the release of carbon dioxide led to ocean acidification, impacting marine life and disrupting food chains. The combination of these factors resulted in widespread oceanic anoxia (low oxygen levels) and the collapse of marine ecosystems.

Massive Biotic Extinctions

The Great Dying is estimated to have led to the extinction of about 96% of marine species and 70% of terrestrial vertebrate species. Many dominant groups, including trilobites and large amphibians, were severely affected. The loss of biodiversity and collapse of ecosystems had long-lasting effects on Earth’s evolutionary trajectory.

End-Permian Extinction Horizon

The boundary between the Permian and Triassic periods is marked by a distinct layer of sediment known as the “end-Permian extinction horizon.” This layer contains high levels of iridium and other elements associated with the impact of an extraterrestrial object, although the role of an impact event in the extinction remains debated. One hypothesis is that the Siberian Traps began as a result of a large meteorite strike.

Recovery and the Dawn of the Triassic

After the Great Dying, ecosystems took millions of years to recover. During the Triassic period, new species evolved to fill ecological niches left vacant by the extinctions. The composition of life on Earth changed, leading to the emergence of new dominant groups and the eventual rise of dinosaurs, which started in the mid-Triassic and really took off in the Jurassic period.