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What Was the Great Dying?

R. Kayne
R. Kayne

The Great Dying, formally the Permian-Triassic extinction event, refers to the largest mass extinction of life on Earth in all history. It happened 252 million years ago (mya) at the end of the Paleozoic era between the Permian and Triassic periods, long before dinosaurs roamed.

The world looked much different during the Permian period. The continents had been pushed together by the forces of plate tectonics into a single supercontinent known as Pangea that stretched from the North Pole to the South Pole. The surrounding super-ocean of Panthalassa was full of sponges, corals, starfish, clams, sea scorpions and bony fish. Amphibians crawled in the wetlands and insects explored ferns and primitive trees, while therapsids or strange mammal-like reptiles that resembled forerunners to dinosaurs roamed. But in a time span of just 80,000 years, 95% of all life would become extinct.

The formation of Pangea (also spelled Pangaea) likely contributed to the Great Dying.
The formation of Pangea (also spelled Pangaea) likely contributed to the Great Dying.

Different theories exist to explain the Great Dying, but it may have been a combination of events that led to the mass extinction. The formation of Pangea itself choked off cool oceans that had formerly surrounded smaller continents that now lay with much of their land mass lodged in the hot, dry interiors. The average temperature increased steadily over millions of years as the supercontinent formed. Suitable habitats may have been difficult to find and competition for food may have thinned species, if not caused some outright extinctions. Pangea also changed ocean currents, salinity and weather patterns, upsetting the balance of how life had been evolving. However these changes occurred so slowly it is unlikely to have been more than a contributing factor.

Destruction of the Earth's ozone layer may have been behind the Great Dying.
Destruction of the Earth's ozone layer may have been behind the Great Dying.

A major event that did occur at the same time of the Great Dying was the creation of the Siberian Trapps, formed by volcanic eruptions that continued for one million years. The greatest volcanic event in known history, the gases released would have created acid rains, a greenhouse effect, and global warming. The oceanic repercussions from a rise in temperature along with changes in salinity could have resulted in the disruption of thermohaline circulation or global currents. Stagnation would have resulted in oxygen and nutrient depletions, leading to a global loss of marine life.

If the greenhouse effect created by prolonged volcanism raised oceanic temperatures enough, it would have triggered yet another repercussion for which there is scientific evidence: methane hydrate gasification.

Starfish and other sea life lived in the prehistoric ocean Panthalassa.
Starfish and other sea life lived in the prehistoric ocean Panthalassa.

Paul Wignall found that a carbon isotope signature in strata from Greenland dating to the time of the Great Dying indicated a marked increase of carbon-12, unaccountable by standard explanations. Geologist Gerry Dickens suggested that a rise in deep-sea temperatures would have released frozen methane hydrate from the seabeds, freeing catastrophic amounts of methane gas. This would have welled up through the oceans and been released into the atmosphere, accounting for the signature in the strata. Methane gas is yet another powerful greenhouse gas. The volume released would have raised the average temperature again another 9 degrees Fahrenheit (5 degrees Celsius). This would be sufficient to kill most life.

During the Permian period, the continents were pushed together by the forces of plate tectonics.
During the Permian period, the continents were pushed together by the forces of plate tectonics.

Theories with lesser evidence suggest an impact from a comet or meteor, but there is little to no proof of this as a cause of the Great Dying, while there is ample proof of such an impact being responsible for bringing the reign of the dinosaurs to an end some 187 million years later. Another theory suggests that a supernova event within ten parsecs (32.6 light-years) of Earth could have destroyed the protective upper ozone layer for several years. This layer of ozone filters out ultra-violet (UV) radiation from the sun. Without it, UV rays would kill nearly all life on land and in the seas. There is some geological evidence that brief periods of ozone destruction occurred, but the record is inconclusive on this theory.

The Great Dying or Permian-Triassic extinction was the largest known catastrophe in history. However it did clear the way for the next great event that would come 25 million years later: the birth of the dinosaur and the Age of the Reptiles.

Frequently Asked Questions

What was the Great Dying?

The Great Dying, also known as the Permian-Triassic extinction event, was the most severe extinction event in Earth's history. Occurring approximately 252 million years ago, it eradicated about 96% of marine species and 70% of terrestrial vertebrate species. This catastrophic event reshaped life on Earth, paving the way for the rise of dinosaurs.

What caused the Great Dying?

While the exact cause remains a topic of scientific debate, several factors are thought to have contributed to the Great Dying. Volcanic activity leading to climate change, anoxia (lack of oxygen) in the oceans, and potentially asteroid impacts are among the leading theories. These events likely triggered a cascade of environmental changes that proved devastating for life on Earth.

How long did the Great Dying last?

The duration of the Great Dying is estimated to have been relatively rapid in geological terms, spanning roughly 60,000 years. The onset of the extinction event may have been even quicker, with some evidence suggesting a significant portion of the biodiversity loss occurring over a period of just a few thousand years.

What were the ecological impacts of the Great Dying?

The ecological impacts of the Great Dying were profound, with the loss of so many species leading to a complete restructuring of ecosystems. It took millions of years for biodiversity to recover, and the types of species that dominated the planet changed significantly, with many new groups emerging in the Triassic period that followed.

Did any species benefit from the Great Dying?

While the Great Dying was catastrophic for most life forms, some species did benefit in the aftermath. For example, the ancestors of modern mammals and dinosaurs were among the groups that diversified and filled the ecological niches left vacant by the extinction. This set the stage for the eventual dominance of dinosaurs in the Mesozoic era.

What lessons can we learn from the Great Dying?

The Great Dying illustrates the fragility of Earth's biosphere and the potential for rapid environmental changes to cause mass extinctions. It serves as a stark reminder of the interconnectedness of life and the importance of maintaining biodiversity. Understanding past extinction events helps scientists predict and mitigate the impacts of current and future ecological crises.

Discussion Comments

anon258548

Can anyone tell me how Pangea caused the ocean currents to change?

TrogJoe19

While it may be unlikely that a comet caused the great dying, it is nevertheless likely that a comet will one day hit the earth and cause great devastation to our atmosphere, possibly eliminating all life. This has been a topic of fear among many people, especially with seemingly imminent threats of a comet approaching coming from theories in the scientific community. The likelihood of such an event happening in the near future is, however, very slim, and it is even less likely that such a disaster would cause mass extinction.

BioNerd

The incredible events that were necessary to form the earth as it is today are stunning to think about. The Great Rift Valley of Africa was the source of human life, but before that, it was one of the most chaotic places on earth, with massive volcanic eruptions and splitting of the earth. To this day, the hottest places on earth are the drained salt lakes of Tanzania.

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    • The formation of Pangea (also spelled Pangaea) likely contributed to the Great Dying.
      By: designua
      The formation of Pangea (also spelled Pangaea) likely contributed to the Great Dying.
    • Destruction of the Earth's ozone layer may have been behind the Great Dying.
      By: designua
      Destruction of the Earth's ozone layer may have been behind the Great Dying.
    • Starfish and other sea life lived in the prehistoric ocean Panthalassa.
      By: Giuseppe Porzani
      Starfish and other sea life lived in the prehistoric ocean Panthalassa.
    • During the Permian period, the continents were pushed together by the forces of plate tectonics.
      During the Permian period, the continents were pushed together by the forces of plate tectonics.