[DLS] Robin Wordsworth (Harvard)

“New Leads in a Cold Case: Triggers and Dynamics of Neoproterozoic Snowball Earth”

The Neoproterozoic low-latitude glaciations are some of the most iconic events in Earth’s entire geologic record, but their interpretation remain contested. Were these glaciations Snowballs, Slushballs, or something else? What caused them to occur in a narrow window ca. 700 million years ago and not before or after? What was their effect on the emergence and diversification of complex life? Here I present some of our latest ideas on this topic. First, I show based on Monte Carlo carbon cycle modeling that weathering of the Franklin Large Igneous Province (LIP) was the most likely trigger of the first glaciation, the Sturtian. Earth may have been uniquely sensitive to LIP-induced weathering in the Neoproterozoic, because the response of climate to weathering perturbations depends on both background CO₂ levels and the biological carbon cycle. Model results also indicate Franklin LIP weathering could have pushed Earth into a limit cycle regime involving repeated Snowball events. Sturtian deposits from a Snowball limit cycle rather than a single event can explain the anomalously long duration (~56 My) of the glaciation. Multiple Snowballs imply Sturtian syn-glacial sediments, potentially resolving the Snowball vs. Slushball controversy. Finally, limit cycling removes the requirement for global ocean anoxia throughout most of the Sturtian and its immediate aftermath. This new view of the Cryogenian has significant implications for the survival and evolution of complex life, as well as the habitability of Earth-like exoplanets.

EAPS Department Lecture Series —

Weekly talks aimed to bring together the entire EAPS community, given by leading thinkers in the areas of geology, geophysics, geobiology, geochemistry, atmospheric science, oceanography, climatology, and planetary science. Runs concurrently with class 12.S501.

Contact: eapsinfo@mit.edu