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What It Means

Jerry-Full-Res

Jerry Mitrovica adjusts field measurements of fossil beaches to account for changes Earth has undergone since the sea retreated in the Pliocene, around 3 million years ago. The Pliomax team needs field data collected at many sites from around the world before they can estimate Pliocene sea level with a high degree of confidence.

Photo by Simon Wermuller von Elgg

Previous researchers have produced widely varying estimates of sea level during the Pliocene, ranging from about 16 feet to 130 feet above present sea level. The Pliomax team hopes to narrow that range considerably.  After several years of research, they’ve identified and measured the elevation of Pliocene era beaches on three continents, some of them 90 feet above present sea level. But, so far, the team isn’t ready to propose a new estimate of Pliocene sea level.

Making adjustments to field measurements of the present elevation of Pliocene beaches has proven difficult as the team has identified many new influences that need to be corrected for. Many of the forces that cause land to rise and fall in time are still poorly studied. Estimating the effects on sea level of the changing sizes and shapes of the polar ice sheets has required creating highly detailed estimates of how the ice ages evolved. More fieldwork will give this research group the data they need to refine their understanding of the motion of the Earth’s crust through time. The Pliomax team continues looking for new Pliocene sites to study. They also collaborate with and encourage other researchers around the world to contribute measurements. They hope that as data accumulates and as they develop new techniques for correcting measurements the most accurate estimates of Pliocene Sea level will emerge.