The Ordovician-Silurian extinction event was the first of the so-called Big Five mass extinctions in Earth's history, occurring about 444 million years ago. It affected mainly marine life, since animals had not yet moved widely onto land, and it eliminated a large share of marine species, particularly brachiopods, trilobites, graptolites and corals. It happened in two pulses and is generally linked to climate change: a short, intense glaciation in the southern supercontinent Gondwana lowered sea levels and cooled the oceans, followed by a warming that reduced oxygen in deeper waters. The causes of the cooling are still debated. Life recovered over millions of years during the Silurian, as new groups diversified.
Before and after
- from about 3.92 billion years ago to 3.85 billion years agoNectarian
- from about 2.4 billion years ago to 2.1 billion years agoHuronian glaciation
- from about 1.8 billion years ago to 800 million years agoBoring Billion
- about 543 million years agoCambrian explosion
- about 444 million years agoOrdovician–Silurian extinction event
- from about 380 million years ago to 280 million years agoVariscan orogeny
- about 375 million years agoFish with limbs begin to walk: tetrapods evolve
- about 372 million years agoLate Devonian extinction
- about 252 million years agoPermian-Triassic mass extinction
More in Evolution & life
- about 66 million years agoCretaceous-Paleogene mass extinction
- from c. 3,300 BCE to 600 BCEBronze Age
- from 3rd millennium BCE to 2nd millenniumMaya civilization
- from 13th century BCE to 6th centuryAncient Greece
- from 1200 to 1523Aztec
- 24 November 1974Discovery of Lucy
The era
This moment belongs to the Paleozoic (539 million years ago to 252 million years ago), from the first animals to the first forests.