Late Ordovician glaciation

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The Late Ordovician glaciation happened about 440–460 million years ago. It also called the Hirnantian glaciation. Its centre was the Sahara region in late Ordovician, about 440–460 mya (million years ago).

It was probably the cause of the Ordovician-Silurian extinction event.[1] Evidence of this glaciation can be seen in places such as Morocco, South Africa, Libya, and Wyoming (which at the time were near together).

More evidence is got from isotopic data. During the Late Ordovician, tropical ocean temperatures were about 5 °C cooler than present day. This would have been a major cause of the glaciation.[2]

The Late Ordovician had a major mass extinction of nearly 61% of marine life.[3] Estimates of peak ice sheet volume range from 50 to 250 million cubic kilometers, and its duration from 35 million to less than 1 million years. There were also two peaks of glaciation.[2] Glaciation of the Northern Hemisphere was slight because most of the land was in the Southern Hemisphere.

Sources[change | change source]

  1. Delabroye, A.; Vecoli, M. (2010). "The end-Ordovician glaciation and the Hirnantian Stage: a global review and questions about the Late Ordovician event stratigraphy". Earth-Science Reviews. 98 (3–4): 269–282. Bibcode:2010ESRv...98..269D. doi:10.1016/j.earscirev.2009.10.010.
  2. 2.0 2.1 Finnegan, S. (2011). "The magnitude and duration of the Late Ordovician-Early Silurian glaciation" (PDF). Science. 331 (6019): 903–906. Bibcode:2011Sci...331..903F. doi:10.1126/science.1200803. PMID 21273448.
  3. Sheehan, Peter M (1 May 2001). "The Late Ordovician Mass Extinction". Annual Review of Earth and Planetary Sciences. 29 (1): 331–364. Bibcode:2001AREPS..29..331S. doi:10.1146/annurev.earth.29.1.331.