From time to time, life on Earth has endured untold misery. Catastrophic events have wiped out billions of lives from the face of this planet. For some species, these catastrophes meant complete annihilation. For others, only the strongest lived and learned to adapt. The Ordovician-Silurian Mass Extinction is one such event. It is considered to the planet Earth’s second-most devastating extinction event, ranking second after the Great Dying. Let us today learn 25 interesting Ordovician-Silurian Mass Extinction facts and find out what really happened and who suffered.
Interesting Ordovician-Silurian Mass Extinction Facts: 1-13
1. The Ordovician-Silurian Mass Extinction was the second largest mass extinction that took place on earth. The largest was the Great Dying.
2. This event is sometimes referred to as Ordovician Extinction or End-Ordovician Extinction.
3. This extinction event took place during the Hirnantian Age of Ordovician Period and the subsequent Rhuddanian Age of the Silurian Period.
4. The Hirnantian Age lasted from 445.6 m.y.a. to 443.7 m.y.a. while the Rhuddanian Age lasted from 443.7 m.y.a. to 439 m.y.a. Please note that m.y.a. stands for ‘Million Years Ago’.
5. According to experts, this extinction event took place in two phases that were separated by a million years.
6. As far as the severity of the event was concerned, it wiped out over 60% of marine invertebrate life forms. The most interesting thing to know about the Ordovician Period is that there were no land-based animals during that period. All life forms were confined to the oceans.
7. Most badly hit were the bryozoan and brachiopod families. About two-thirds of these families went extinct.
8. In particular, corals, bryozoans, echinoderms, bivalves and brachiopods were most affected.
9. Scientists have for long argued that the mass extinction was caused by an ice age when one of the four supercontinents – Gondwana moved to the South Pole.
10. As large ice sheets formed over the Gondwana, the oceans were drained out of water. Ocean levels dropped by 70 to 100 meters.
11. This fall in ocean levels mostly affected the life forms that lived in shallow waters such as the bryozoans and the corals.
12. The condition lasted for about a million years during which the global temperatures dropped. Life forms that were adapted to warm environmental conditions perished gradually.
13. After 1 million years of ice age came the interglacial period (relatively warmer period with higher global temperatures). It was during this interglacial period that the ice sheets released water.