Ordovician Period
485.4 – 443.8 million years ago · Paleozoic Era
The Ordovician saw one of the biggest bursts of biodiversity in Earth history, the Great Ordovician Biodiversification Event. Marine life multiplied into reefs, shellfish and early fish, while the first plants began to colonize land.
At a glance
- Began
- 485.4 Ma
- Ended
- 443.8 Ma
- Duration
- 41.6 million years
- Era
- Paleozoic
- Climate state
- Transitional (warm with glacial episodes)
- Land above sea level (PaleoDEM)
- ~20.8%
- Dinosaurs on our map
- 0
The world in the Ordovician
Open the interactive map at 460 Ma → Elevation view
What Earth was like
Gondwana drifted south until North Africa sat over the South Pole. The smaller continents Laurentia, Baltica and Siberia remained near the equator, separated by the Iapetus Ocean, which slowly began to close. Sea levels were among the highest of the whole Phanerozoic.
Climate
For most of the period the climate was warm, but it cooled toward the end. A short, intense ice age in the Late Ordovician built ice sheets across Gondwana, locking up water and draining the shallow seas.
Life
Brachiopods, bryozoans, crinoids, nautiloids and trilobites flourished, and the first coral reefs formed. Jawless fish swam in the seas. On land, the earliest liverwort-like plants left spores behind, the first step toward green continents.
Dinosaurs of the Ordovician
There were no dinosaurs yet. The first dinosaurs appear in the Late Triassic, around 233 million years ago.
How it ended
The end-Ordovician mass extinction, one of the "Big Five", wiped out roughly 85% of marine species in two pulses tied to the glaciation and the sea-level crash that came with it.
Key facts
- The end-Ordovician extinction was the second largest in Earth history by share of species lost.
- The Sahara holds glacial deposits from the Ordovician ice age.
- Fossil spores show plants reached land around 470 million years ago.
Data: land and sea
Across the Ordovician, an average of 20.8% of Earth’s surface stood above reconstructed sea level (range 20.2–21.9%). Today the same model gives 31.8%.
Where this data comes from
- Continent positions: GPlates Web Service, Merdith et al. (2021) full-plate model, used for 250–540 Ma.
- Elevation and shorelines: PALEOMAP PaleoDEMs, Scotese & Wright (2018), doi:10.5281/zenodo.5460860, CC BY 4.0.
- Period boundaries: ICS International Chronostratigraphic Chart (2023/09).
These are scientific reconstructions, not observations. Uncertainty grows the further back in time you go. About & data sources
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