The Great Dying was the largest known mass extinction in Earth history, occurring about 252 million years ago at the boundary between the Permian and Triassic periods. It wiped out most marine species and many land species, reshaping life on the planet. This event matters because it shows how rapidly climate, oceans, and ecosystems can change when Earth systems are pushed far out of balance.
It also helps explain why later ecosystems had open space for new groups, including the early relatives of dinosaurs.
Key Facts
- The Great Dying occurred about 252 million years ago at the Permian-Triassic boundary.
- About 90% to 96% of marine species and about 70% of land vertebrate species disappeared.
- Major Siberian Traps volcanism released large amounts of CO2, SO2, and other gases.
- Greenhouse warming follows the relation greater atmospheric CO2 = stronger heat trapping.
- Ocean acidification can be represented by CO2 + H2O = H2CO3, forming carbonic acid.
- After the extinction, ecological niches opened and new Triassic groups, including early dinosaur relatives, diversified.
Vocabulary
- Mass extinction
- A mass extinction is a short interval in geologic time when an unusually large percentage of species disappear worldwide.
- Permian-Triassic boundary
- The Permian-Triassic boundary is the rock and time boundary about 252 million years ago marking the end of the Permian Period and start of the Triassic Period.
- Siberian Traps
- The Siberian Traps are vast volcanic rock layers in present-day Russia formed by enormous eruptions near the time of the Great Dying.
- Anoxia
- Anoxia is a condition in which water has little or no dissolved oxygen, making it deadly for many aquatic organisms.
- Ecological niche
- An ecological niche is the role a species plays in its environment, including what it eats, where it lives, and how it interacts with other organisms.
Common Mistakes to Avoid
- Saying dinosaurs died in the Great Dying is wrong because non-avian dinosaurs went extinct much later, about 66 million years ago, while the Great Dying happened about 252 million years ago.
- Blaming only one volcano is misleading because the main volcanic activity involved the enormous Siberian Traps province and its global effects on climate, oceans, and chemistry.
- Thinking extinction happened instantly is wrong because the crisis likely unfolded over thousands to hundreds of thousands of years, which is fast geologically but not a single day.
- Ignoring ocean chemistry gives an incomplete explanation because warming, acidification, and anoxia were major reasons marine ecosystems collapsed.
Practice Questions
- 1 If 95% of marine species went extinct during the Great Dying and there were 20,000 marine species before the event, how many marine species survived?
- 2 The Great Dying occurred about 252 million years ago, and the end-Cretaceous extinction occurred about 66 million years ago. How many million years separate these two extinction events?
- 3 Explain why a mass extinction that removed many dominant Permian species could make it easier for new Triassic groups, including early dinosaur relatives, to diversify.