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 the record matches only a handful of times, with Siberia and South China erupting in the same interval. Uranium and lead in the intruded rock date the episode between 719.9 and 718.6 million years ago. Nine hundred thousand to a million and a half years later, ice reached sea level at the equator.

Why it matters

Volcanoes are how the planet warms itself: they exhale carbon dioxide. This one appears to have done the reverse, and slowly. The erupted basalt 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 by itself.

Dating & uncertainty

Uranium and lead dating of the Franklin sills gives 719.86 ± 0.21 to 718.61 ± 0.30 Ma, one to two 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