“The Five Mass Extinctions That Changed Life on Earth Forever”

1. Ordovician–Silurian Extinction (≈444 million years ago)

Impact: ~85% of marine species went extinct.

What happened:

• Earth experienced a sudden ice age.

• Massive glaciers formed and sea levels dropped dramatically.

• Shallow seas, where most life existed, disappeared.

Life affected:

• Trilobites

• Brachiopods

• Coral-like organisms

• Many early marine invertebrates

Why it matters:
At the time, most life existed in the oceans. This extinction reorganized marine ecosystems and opened evolutionary space for new species.

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2. Late Devonian Extinction (≈372–359 million years ago)

Impact: ~75% of species disappeared.

What happened:

• Extinction occurred in multiple pulses over millions of years.

• Possible causes include:

  • ocean oxygen loss (anoxia)

  • climate change

  • asteroid impacts

  • volcanic activity

Life affected:

• Coral reef ecosystems collapsed.

• Many armored fish (placoderms) vanished.

Why it matters:
It ended the dominance of early armored fish and helped pave the way for the rise of modern fish lineages and early land vertebrates.

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3. Permian–Triassic Extinction (“The Great Dying”) (≈252 million years ago)

Impact:

• 96% of marine species

• 70% of land vertebrates

This is the largest extinction in Earth’s history.

What happened:

• Massive volcanic eruptions in the Siberian Traps.

• Huge amounts of CO₂ released.

• Global warming, ocean acidification, and oxygen collapse.

Life affected:

• Trilobites disappeared forever.

• Many insect groups died out.

• Forest ecosystems collapsed.

Why it matters:
Life on Earth nearly ended. Recovery took 10 million years.

4. Triassic–Jurassic Extinction (≈201 million years ago)

Impact: ~80% of species went extinct.

What happened:

• Massive volcanic eruptions during the breakup of Pangaea.

• Climate change and CO₂ spikes.

Life affected:

• Many large amphibians vanished.

• Numerous reptile groups disappeared.

Why it matters:
After this extinction, dinosaurs became the dominant animals on land for the next 135 million years.

5. Cretaceous–Paleogene Extinction (≈66 million years ago)

Impact: ~75% of species disappeared.

What happened:

• A 10–12 km asteroid struck Earth near the Yucatán Peninsula.

• The impact created the Chicxulub crater.

• Dust blocked sunlight → global cooling → ecosystem collapse.

Life affected:

• All non-avian dinosaurs

• Many marine reptiles

• Ammonites

Why it matters:
This extinction allowed mammals to rise, eventually leading to the evolution of humans.

The Bigger Picture

These five extinction events reshaped life on Earth:

Some scientists believe Earth may now be entering a Sixth Mass Extinction, driven largely by human activity.