Mass Extinctions in Earth History
Compare the five major mass extinction events in Earth history (End-Ordovician, Late Devonian, End-Permian, End-Triassic, K-Pg), describe proposed kill mechanisms for each (glaciation, oceanic anoxia, volcanic mega-eruptions, asteroid impact), and explain why mass extinctions, while catastrophic, also open ecological space for subsequent evolutionary radiations
What a learner can do afterwards
- Names all five major mass extinctions in chronological order with approximate dates
- Describes the End-Permian extinction as the most severe and links it to the Siberian Traps volcanic eruption and its atmospheric consequences
- Explains how each mass extinction was followed by an adaptive radiation — e.g. the K-Pg extinction removing non-avian dinosaurs allowed mammals to diversify and eventually produce humans
The lesson
You already know that an asteroid ended the age of the dinosaurs. That event is called the K-Pg extinction. Here is the surprising part: it was not the first mass extinction, and it was not even the worst one. It was the fifth of five giant die-offs in Earth's history.
The worst mass extinction of all happened at the end of the Permian period, about 252 million years ago. Scientists call it the Great Dying. In Siberia, volcanoes erupted for thousands of years, covering an area bigger than the United States in lava. The eruptions pumped so much carbon dioxide into the air that the planet heated up, rain turned acidic, and oxygen disappeared from much of the ocean. Around 96 percent of ocean species died out.
Every mass extinction, even the worst one, eventually led to something new. When a die-off clears out crowded ecosystems, the species that survive get room to spread out and evolve into new forms. You already know this happened after K-Pg: once the non-avian dinosaurs were gone, mammals filled the empty space and, millions of years later, produced humans.
Earth has had five mass extinctions, each caused by a different disaster, and each one cleared space for surviving life to evolve into something new.
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8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.