China-sized lava eruption may have frozen Earth 717 million years ago

This latest study and another published in Science Advances last year have provided more precise dates, indicating that the volcanic eruptions preceded the Snowball Earth event by 1 to 2 million years.  

Significantly, the time lag points to a specific mechanism by which the volcanic activity triggered the ice age: weathering. This process extracts carbon dioxide (CO2) from the atmosphere as a planetary thermostat.

This timing rules out an alternative explanation involving the release of sulfur-rich gases, which form aerosols, blocking sunlight and lowering the planet's temperature.

The findings underscore the influential role of weathering in driving shifts in Earth's climate, showcasing the intricate connection between different components of the planet, from rocks to the atmosphere, explains Galen Halverson, co-author of the EPSL study and a sedimentary geologist at McGill University. 

"Nothing can be understood in isolation," he emphasized in a Science article.

The Franklin LIP formed a vast volcanic highland that likely endured intense weathering due to its exposure to wind and water, further supporting the weathering-trigger hypothesis.

Dating using Zircon crystals

To reach these timely conclusions, the team utilized trace amounts of uranium and lead trapped in tiny zircon crystals. They discovered that the Franklin LIP formed in about 2 million years, significantly faster than previously thought.

The main volcanic activity occurred 1 to 2 million years before Snowball Earth, as revealed by the analysis of rocks carried by glaciers and deposited in the ocean.

While these findings offer a compelling explanation for one of Earth's ancient ice ages, some uncertainties remain. Notably, the exact timing of the global glaciation is still a topic of debate among researchers. 

The possibility of other factors amplifying the weathering effect during the Franklin LIP eruptions is also being explored. Snowball Earth events after 650 million years, which lacked preceding volcanic eruptions, remain enigmatic. 

Still, Linda Sohl, a paleoclimatologist at Columbia University, not involved in the study, suggests weathering may have been a key factor during these events, too, as earlier Snowball Earth glaciation exposed fresh rock.

“At the very least, a revisit with weathering models seems in order...The snowball glaciations are such fascinating events that are going to keep all of us quite busy for years to come," she concluded. 

The complete study was published in Earth and Planetary Science Letters and can be found here.

Study abstract:

The Franklin igneous event (ca. 718 Ma) emplaced basalts and mafic intrusions across Arctic Laurentia just prior to the onset of the ca. 717–661 Ma Sturtian Snowball Earth event. Given the close association in time between these two events, it has been widely argued that the Franklin event contributed to the initiation of global glaciation. However, a lack of accurate high-precision geochronology has hampered establishing the timeframe of Franklin magmatism and discerning its precise temporal and possible causative relationship to glaciation. Here we present new high-precision U-Pb CA-ID TIMS zircon ages for two dykes and two sills from Baffin Island, Canada, and Avannaata, northwestern Greenland, related to the Franklin event. Combined with field relationships showing that the dykes crosscut the sills, these four dates indicate magmatic activity over Myr at ca. 718 Ma, immediately prior to Sturtian glaciation, which we estimate to have initiated at 717.19 +0.26/−0.33 Ma. Our results are consistent with recent high precision U-Pb CA-ID TIMS age estimates for the Franklin magmatic activity in the central and western parts of the province. Combining our new dates with the other high precision CA-ID-TIMS ages yields a duration for the Franklin event of Myr which is shorter than the previous estimates but somewhat longer than that for typical Phanerozoic large igneous events.