Snowball Events Timed for Advanced Life | News of the Day

Join Hugh Ross in this breaking News of the Day episode of Stars, Cells, and God. Hugh describes the first accurate dating of the beginning and end of the Sturtian snowball event—which covered over 80% of Earth’s surface with thick ice—and how this precise timing made advanced life possible. Previous attempts to date the Sturtian snowball event were based on five or less detrital zircons. Geologists recovered more than 2,000 detrital zircons from the Port Askaig Formation in Scotland, where advancing and retreating glaciers had not eroded away the historical record of the Sturtian. In the words of lead author Elias J. Rugen, “by some miracle the transition can be seen.” Uranium-lead isotope measurements of the zircons yielded radiometric dates for when the sedimentary layers in the Port Askaig Formation transitioned from warm tropical to cold glacial conditions and back again. The uranium-lead derived ages showed that the Sturtian snowball event lasted from 720 to 663 million years ago. The Sturtian event dramatically reduced carbon dioxide and dramatically increased oxygen in Earth’s atmosphere. If the Sturtian event had occurred any earlier, then the Sun would have been too dim to prevent Earth from being permanently covered with ice. On the other hand, if the Sturtian event had occurred any later, then the brighter Sun would have shortened the duration and limited the ice coverage, resulting in too little oxygen and too much carbon dioxide in Earth’s atmosphere, ruling out the possibility of advanced life. Links and Resources: Glacially Influenced Provenance and Sturtian Affinity Revealed by Detrital Zircon U–Pb Ages from Sandstones in the Port Askaig Formation, Dalradian Supergroup Hugh Ross, Designed to the Core, 218–220.