The Ordovician-Silurian Extinction Event was a mass extinction brought about, not only by the Ordovician glaciation, but a combination of "reduced shelf and platform habitable space, diminishing temperatures and perturbation of the ocean stratification and circulation systems "(Gradstein, 2012). The life that was slowly starting to develop on land was cut short by the freezing temperatures and ice age. Wiping out at least half of the marine animal life on Earth, this is the second largest mass extinction of all time ("Ordovician period and").
At the close of the devastating end to the Cambrian Period, due to a multitude of changes to the environment, the Ordovician Period began with the appearance of "an extraordinarily wide range of 'Cambrian-, Paleozoic and Modern-type' biotas" (Webby, 2004). The event was the greatest increase in marine diversity in Earth's history, replacing those organisms that didn't survive the Cambrian. Earth was finally healing.
The Ordovician-Silurian Extinction Event
The Great Ordovician Biodiversification Event
Major Events
Fun Facts!
By: Katherine Clough
Organisms
References
What Did The Earth Look Like?
ORDOVICIAN PERIOD
Beginning 488.3 million years ago and ending 447.3 million years ago, the Ordovician Period lasted for almost 45 million years!
Gradstein, Felix M., et al. “Chapter 20 - The Ordovician Period.” The Geologic Time Scale 2012, Elsevier, Oxford, 2012, pp. 489–518, ebookcentral.proquest.com/lib/ucf/reader.action?docID=980015&ppg=519&pq-origsite=primo. “Ordovician Facts For Kids.” Kiddle, Kiddle Encyclopedia,26 July 2023, kids.kiddle.co/Ordovician. “Ordovician Period and Facts.” National Geographic,National Geographic Society, 3 May 2021, nationalgeographic.com/science/article/ordovician#:~:text=For%20the%20most%20part%20the,Africa%20at%20the%20supercontinent’s%20center. “Ordovician Period-485.4 to 443.8 MYA.” National Park Service, National Park Service U.S. Department of the Interior, 28 Apr. 2023, nps.gov/articles/000/ordovician-period.htm#:~:text=Movement%20of%20life%20onto%20land,the%20ocean%20(Rogers%201993). Webby, Barry, et al. The Great Ordovician Biodiversification Event. Columbia University Press, 2004, ProQuest Ebook Central, ebookcentral.proquest.com/lib/ucf/reader.action?docID=908991.
Works Cited
- Named by Charles Lapworth in 1879, because fossils during this time period were different from that of the Cambrian and Silurian ("Ordovician Period For")
- Named after a Welsh tribe, the Ordovices ("Ordovician Period For")
- The major landmass, Gondwana, included what is known today as Africa, South America, Antarctica, and Australia
- The mountain-building that eventually led to the formation of the Appalachian Mountains begain in Mid-Ordovician time ("Ordovician Period-485.4")
Fun Facts!
Evidence that primitive plants, called lycophytes, first started to grow on land during the Ordovician Period exists "in the form of dispersed microfossils: spores and phytodebris" (Webby, 2004). In order to have colonized the land as they did, the first plants are speculated to have been nonvascular (bryophytelike) and confined to somewhat damp environments. Their arrival, in combination with other environmental conditions, is theorized to have led to the mass extinction event that ended the Ordovician.
Plant Life
Ordovocian Period Organisms
Animal Life
The Ordovician Period gave rise to a thriving variety of marine life, and the first animals and plant life to appear on land. With the Great Ordovician Biodiversification Event, organisms evolved to replace those that died off at the end of the Cambrian, such as nautiloid cephalopods, bryozoans (moss animals), and conodonts. Nautiloids were a type of tentacled mollusk that were efficient swimmers who used their tentacles to grasp prey. The few fossils of conodonts suggest that "they were finned, eel-like creatures with large eyes for locating prey ("Ordovician Period and"). According to the fossil record, the first true fish, ostracoderms, jawless and possessing bony plates, and coral reefs evolved during this time. In the Late Ordovician, hard-bodied arthropods, such as the horseshoe crab, were the first form of animal life to leave the ocean and step on land ("Ordovician Period and").
Overview
Moving Continents
As depicted above, the continents during the Ordovician Period started to come together to form new landmasses and islands, and, therefore, new isolated habitats. Much of the landmasses we know today were submerged, subjecting the Earth to extreme evaporation rates that "produced an increased cloudiness with a feedback to reduce incoming insolation" (Webby, 2004). This phenomena contributed greatly to the greenhouse state of the Earth; a world without polar icecaps due to its "warm climate with wide-tropical and warm temperature marine-belts" (Webby, 2004).
What Did The Earth Look Like?
Many of the specific conditions of the Ordovician Period of the Paleozoic era are highly speculated and in need of greater investigation. It is confirmed, however, that the Earth, then, is very different from how we know it today.Some of the accepted prevailing conditions, at least, before the Ordovician-Silurian Extinction event, include:
- high levels of greenhouse gases in the atmosphere (carbon dioxide)
- increase in oxygen levels in the oceans
- "Periods of increased volacinity" (Webby, 2004)
- "A sluggish surface and deep ocean circulation, due to the overall greenhouse state" (Webby, 2004)
- Warm and wet climate with sea levels about 600 meters above those of today ("Ordovician Period and")
