EARTH × CLIMATE

The Eruptions That Froze the World

~720 to 717 million years ago

Proterozoic · Neoproterozoic · Cryogenian

Magma forced its way through the crust of what was then equatorial Canada, on a scale matched only a handful of times in the geological record; Siberia and South China erupted in the same interval. Uranium and lead in the intruded rock date the episode between 719.9 and 718.6 million years ago. Between 0.9 and 1.6 million years later, ice reached sea level near the equator.

Why it matters

Volcanoes are how the planet warms itself: they exhale carbon dioxide. This episode appears to have done the reverse, and slowly. The eruptions may have raised highlands in the wet equatorial belt, and fresh basalt weathering in the rain pulls carbon dioxide out of the air faster than almost any other rock. Take enough of it out and the ice, which reflects sunlight away, does the rest.

Dating & uncertainty

Uranium and lead dating of the Franklin sills gives 719.86 ± 0.21 to 718.61 ± 0.30 Ma, 0.9 to 1.6 million years before the ice. The dating is tight; the causal chain is not. Whether fresh basalt weathering or sulfate aerosols in the stratosphere did the cooling has been simulated, never watched.

Sources

1. Pu et al. (2022), Science Advances · Emplacement of the Franklin large igneous province and initiation of the Sturtian Snowball Earth
2. Lu et al. (2022), Earth and Planetary Science Letters · Widespread magmatic provinces at the onset of the Sturtian snowball Earth
3. Minsky et al. (2025), Journal of Geophysical Research: Planets · Neoproterozoic Snowball Earth initiation from silicate weathering of a large igneous province

Earth history as one day

20:11:373 h 48 min before midnight

if Earth’s 4.54 billion years were compressed into a single day