Colorado College Professor of Geology Paul Myrow is the lead author on the article “Rapid Sea Level Rise in the Aftermath of a Neoproterozoic Snowball Earth,” published in the journal Science in early May. He co-authored the article with Ryan Ewing ’98, who was a CC geology student and is now an associate professor of geology and geophysics at the University of Texas A&M. A third researcher on the paper is Michael Lamb, professor at California Institute of Technology.
The team of researchers discovered geological evidence in Southern Australia supporting what is known as the Snowball Earth hypothesis, which concerns episodes in Earth history when the entire surface was encased in ice. The paper estimates the rate of sea level rise during rapid melting at the end of a Snowball Earth glaciation.
“There were two such events toward the end of the Precambrian Eon, in an interval between approximately 717 and 635 million years ago. These events profoundly altered Earth’s atmosphere, oceans, and biosphere, and may have had a profound effect on the evolution of life, in part because the Earth shifted from an icehouse to an extreme greenhouse climate,” says Myrow.
The Snowball Earth era ended with cataclysmic melting of the ice sheets, which raised sea levels radically. Myrow says they calculate an estimated rate of sea level rise of about 28 centimeters a year, which is 100 times the present-day rate.
“One prediction of the Snowball Earth model is that the thick ice sheets that covered both oceans and land would have melted very quickly — a few thousand years — generating a vast amount of meltwater that would have been delivered to the ocean, raising sea level by more than 1,000 meters,” he says.
The team, which traveled to Australia's Adelaide Rift Complex and Stuart Shelf in 2014, used the size and shape of preserved ripples, created in the sand bed of the ancient oceans, to determine the oceanographic conditions, including approximate water depths. Not only was the rate of sea level rise 100 times greater than present-day rates, the proposed rate of sea level rise is also five times greater than the highest rates recorded for the last ice age (Pleistocene) deglaciation, Myrow says.
“Sea-level rise of this magnitude is a strong confirmation of a major tenet of the Snowball Earth hypothesis, namely rapid deglaciation during the early transition from icehouse to hyper-greenhouse conditions. It also likely represents the largest possible rate of sea level rise for any time in Earth history,” he says. “That is a reminder that Earth systems can change dramatically over geologically relatively short time scales.”
Myrow notes that an added benefit of the project was working with his former student Ewing, with whom he has kept in touch over the years. Ewing, who received his Ph.D. from the University of Texas, Austin, is a leading scientist in the field of sedimentology and has worked extensively on the interpretation of Martian data.