The 6 Mass Extinctions Earth Has Experienced
Earth has experienced five major mass extinctions in its history, with many scientists arguing that we are currently in the midst of a sixth. Here’s a summary of each:
1. Ordovician-Silurian Extinction (c. 443 million years ago)
- Cause: Likely due to a sudden global cooling event followed by a rapid warming period, leading to sea-level changes.
- Impact: Around 85% of marine species were wiped out, including many trilobites, brachiopods, and graptolites.
2. Late Devonian Extinction (c. 375–360 million years ago)
- Cause: Possibly triggered by volcanic activity, climate change, or a drop in oxygen levels in the oceans.
- Impact: Around 75% of species vanished, particularly affecting marine life, including reef-building organisms.
3. Permian-Triassic Extinction ("The Great Dying") (c. 252 million years ago)
- Cause: Massive volcanic eruptions (Siberian Traps), climate shifts, and ocean acidification.
- Impact: The worst mass extinction, wiping out 96% of marine species and 70% of terrestrial species, including early reptiles and amphibians.
4. Triassic-Jurassic Extinction (c. 201 million years ago)
- Cause: Linked to massive volcanic eruptions (Central Atlantic Magmatic Province), leading to global warming and ocean acidification.
- Impact: Around 80% of species went extinct, allowing dinosaurs to become the dominant land animals.
5. Cretaceous-Paleogene (K-Pg) Extinction (c. 66 million years ago)
- Cause: A massive asteroid impact (Chicxulub crater, Mexico) and volcanic activity (Deccan Traps).
- Impact: About 75% of all species were lost, including all non-avian dinosaurs, paving the way for mammalian dominance.
6. The Sixth Mass Extinction (Holocene/Anthropocene) (Ongoing)
- Cause: Human activities—deforestation, habitat destruction, pollution, climate change, and overexploitation of species.
- Impact: Species extinction rates are estimated to be 100–1,000 times higher than natural background rates. Many scientists warn we are in the early stages of a mass extinction event.
This current extinction is unique because it is driven entirely by one species—humans— rather than natural disasters or cosmic events.