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What Killed the Dinosaurs?

Introduction | Asteroid Impact | Volcanism | Mammal Competition | Continental Drift | Conclusion

Hypothesis: Volcanism

Did dinosaurs lose their dominance suddenly or gradually? Some scientists think the answer lies locked within the remnants of long-dormant volcanoes.

Massive beds of ancient lava found around the world depict an Earth 65 to 70 million years ago where volcanic eruptions were commonplace.

According to the volcanism hypothesis, this global-scale volcanic activity spewed so much gas, ash, and dust into the atmosphere that it kept sunlight from reaching Earth's surface. Temperature and plant production plummeted, and dinosaurs and many other organisms that were poorly adapted to the harsh conditions perished.

Evidence for the Volcanism Hypothesis

Lava Flows
Immense lava flows cover nearly 200,000 square miles of the Deccan region of India, reaching depths of more than 6,500 feet in places.

Lava flows like these provide evidence of a rash of volcanic activity for at least 500,000 years leading up to the extinction of the dinosaurs.

Rare Metal
The metal iridium, which is similar to platinum, is very rare on Earth's surface but is more common in asteroids and in molten rock deep within the planet.

Some scientists think the presence of high concentrations of iridium at the geological layer associated with the dinosaur extinction could be the result of extremely large-scale volcanic activity.

Fractured Crystals
These crystals, often called "shocked quartz," show a distinctive pattern of fracturing caused by high-energy impacts or explosions.

Although geologists generally acknowledge that a comet or asteroid impact would cause these fractures, some scientists conclude that they could also be the result of volcanic eruptions.

Fossil Record
A gradual decline in the number of dinosaur species would likely mirror an equally gradual cause of their ultimate extinction. Conversely, a sudden "now you see them, now you don't" end to the dinosaurs implies a catastrophic cause. Depending on location and interpretation, the fossil record seems to say different things.

A gradual decline in the number of dinosaur species would likely mirror an equally gradual process like climate change caused by global volcanism.

-> Did dinosaurs lose the struggle against mammals for food and other resources?

Introduction | Asteroid Impact | Volcanism | Mammal Competition | Continental Drift | Conclusion

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