1. Ordovician-Silurian Extinction: Occurred around 444 million years ago, marking the end of the Ordovician period and the beginning of the Silurian period. This extinction event wiped out approximately 85% of marine species, including many brachiopods, trilobites, and graptolites. The cause is believed to be related to a sudden drop in sea levels and changes in ocean chemistry.
2. Devonian Extinction: Took place around 374 million years ago, separating the Devonian period from the Carboniferous period. This event resulted in the extinction of around 75% of marine species, including many fish species, brachiopods, and corals. The cause is thought to be a combination of factors such as climate change, sea-level fluctuations, and volcanic activity.
3. Permian-Triassic Extinction: Often referred to as "The Great Dying," this extinction occurred around 252 million years ago, marking the transition from the Permian period to the Triassic period. It was the most severe extinction event in Earth's history, wiping out approximately 96% of all marine species and 70% of terrestrial vertebrate species. The cause is believed to be a combination of factors such as massive volcanic eruptions, climate change, and an impact from an extraterrestrial object.
4. Triassic-Jurassic Extinction: This extinction event took place around 201 million years ago, separating the Triassic period from the Jurassic period. It resulted in the extinction of around 75% of marine species, including many marine reptiles, and a significant decline in terrestrial vertebrate diversity. The cause is thought to be a combination of volcanic activity and climate change.
5. Cretaceous-Paleogene Extinction: Often known as the "K-Pg Extinction Event," this occurred approximately 66 million years ago, marking the end of the Cretaceous period and the beginning of the Paleogene period. It is most famous for the extinction of the dinosaurs (except for birds) but also led to the disappearance of many other marine and terrestrial species, including ammonites, marine reptiles, and numerous plant species. The cause is widely attributed to the impact of a large asteroid or comet, combined with volcanic activity and climate change.
These mass extinctions have played crucial roles in shaping the evolution of life on Earth, leading to the rise and fall of various species and ecological communities throughout geological history.