Sturtian glaciation
| Proterozoic snowball periods | ||||||
| −750 — – −725 — – −700 — – −675 — – −650 — – −625 — – −600 — – −575 — – −550 — – −525 — | ||||||
| 
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The Sturtian glaciation was a worldwide glaciation during the Cryogenian Period when the Earth experienced repeated large-scale glaciations. As of January 2023, the Sturtian glaciation is thought to have lasted from c. 717 Ma to c. 660 Ma, a time span of approximately 57 million years. It is hypothesised to have been a Snowball Earth event, or contrastingly multiple regional glaciations, and is the longest and most severe known glacial event preserved in the geologic record after the much earlier Huronian glaciation.