Late Ordovician Glaciation and Mass Extinction
c. 445 Million years ago · Prehistoric
Approximately 445 million years ago, with Gondwana positioned over the South Pole, accelerated CO₂ drawdown from volcanic rock weathering and organic carbon burial drove Earth from greenhouse to icehouse conditions. Continental ice sheets formed, sea levels dropped roughly 100 meters, and two extinction pulses eliminated approximately 85% of marine species. The first pulse resulted from rapid cooling; the second, shorter pulse from rapid warming caused anoxic water to flood continental shelves. Recent geochronological work establishes that the rate of temperature change, not its magnitude alone, controlled extinction intensity.
Locations
Geographic South Pole
Topics
Gondwanaglaciationmarine extinctionmass extinctionocean anoxia
Connected Events — 6 Connections
Gondwana's position over the South Pole enabled ice sheet formation; continental drift would later assemble Gondwana into the supercontinent Pangaea Formation of Pangaea
The Ordovician extinction devastated the marine biodiversity that had flourished since the Cambrian Explosion roughly 90 million years earlier Cambrian Explosion
The Ordovician glaciation was Earth's first major ice age since the Snowball Earth episodes roughly 230 million years earlier, though far less severe in extent Snowball Earth Episodes: Global Glaciations
The Ordovician extinction was the second-largest mass extinction in Earth's history, surpassed only by the Permian-Triassic die-off 193 million years later Permian-Triassic Extinction: The End-Permian Die-Off
Plate tectonics positioned Gondwana over the South Pole and drove the Taconic orogeny whose weathering drew down atmospheric CO₂, triggering the glaciation Onset of Plate Tectonics on Earth
Both events were driven by CO₂ drawdown and glacial intensification, though separated by 140 million years and affecting entirely different ecosystems Carboniferous Rainforest Collapse
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