A recent study led by planetary scientist Trent Thomas from the University of Washington, published in Geology, investigates the varying durations of two Cryogenian Snowball Earth events that occurred between 720 and 635 million years ago. One glaciation lasted 56 million years, while the other spanned just 4 million years. The study examines how differences in the carbon cycle could explain this 14-fold disparity.
Snowball Earth conditions arise when ice sheets expand from the poles towards the equator, reflecting sunlight and further cooling the planet. Despite this frozen state, volcanic emissions continue adding carbon dioxide (CO2) to the atmosphere. Eventually, this buildup can end the glaciation abruptly, ushering in warmer climates.
Thomas and his team developed a computer model to explore whether variations in seafloor weathering might account for the differing glaciation durations. Their simulations suggest that changes in seafloor weathering efficiency—rather than volcanism or continental weathering—likely dictated the length of these Snowball events. Enhanced seafloor weathering during the longer glaciation effectively drew down volcanic CO2, maintaining icy conditions, while slower weathering during the shorter event allowed CO2 to accumulate, ending the glaciation sooner.
The study posits that seafloor porosity, influenced by factors like sulfate content in seawater, could have affected weathering rates. This research highlights a previously underestimated role of seafloor processes in regulating Earth’s ancient climate, pointing to new research avenues about the carbon cycle’s deep-time dynamics.