The story
From roughly 330 to 260 million years ago, glaciers repeatedly spread across Gondwana, which then lay over the South Pole, and covered much of what is now Africa, South America, India, Australia and Antarctica. Glacial deposits such as the Dwyka tillite in South Africa and the Talchir deposits in India record it. Alfred Wegener later used these deposits, which match across oceans, as evidence for continental drift.
The ice age arose partly from the rise of forests. Coal swamps buried enormous quantities of plant carbon, pulling carbon dioxide out of the air and cooling the planet, an idea developed by Robert Berner. Atmospheric carbon dioxide fell to levels close to today's, and oxygen rose. Ice sheets grew and shrank in cycles of tens of thousands to hundreds of thousands of years, moving sea level by 100 metres or more. This pattern, repeated in cyclothems, layered sequences of coal, limestone and shale in Europe and North America, helped build the coal beds. The ice age waned in the Permian as warming and drying spread across Pangaea.
Why it mattered
- The ice age's rhythm of rising and falling seas produced the cyclothems that hold much of the world's coal.
- Its glacial rocks, matching across Africa, India and South America, became key evidence for continental drift.
- The cooling and drying that ended it reshaped land ecosystems, including the Carboniferous rainforest collapse.
Sources
- Timing, Duration and Character of Glaciation During the Late Paleozoic Ice Age AAPG Search and Discovery
- Orbital and CO2 forcing of Late Paleozoic continental ice sheets Penn State
Community notes
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