A neoproterozoic snowball earth

@article{Hoffman1998ANS,
  title={A neoproterozoic snowball earth},
  author={Hoffman and Kaufman and Halverson and Schrag},
  journal={Science},
  year={1998},
  volume={281 5381},
  pages={
          1342-6
        }
}
Negative carbon isotope anomalies in carbonate rocks bracketing Neoproterozoic glacial deposits in Namibia, combined with estimates of thermal subsidence history, suggest that biological productivity in the surface ocean collapsed for millions of years. This collapse can be explained by a global glaciation (that is, a snowball Earth), which ended abruptly when subaerial volcanic outgassing raised atmospheric carbon dioxide to about 350 times the modern level. The rapid termination would have… 
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