Science graph of the week: 5.3 million years of sea level change on a cliff

It is not often that we think about deep time. Fortunate enough to live a century, people flit across the surface of the earth like ephemera, our own epoch a wink in a planetary history that is largely hidden from everyday consciousness.

Every now and then, however, this story strikes through to the present day. And when it does, it’s often a story carved in stone: the fossils Darwin found on a mountaintop, the sandstone formations that made the science of the 18th century a reality.

And that’s the kind of story that is told in the cliffs of Punta di Maita, Italy (photo below). Each band is a layer of sediment on the ocean floor that accumulated long ago over 21,000-year orbital cycles and was eventually forced into its current formation by tectonic activity. They have been made more macroscopic over time – and when microscopic fossils in the layers were analyzed by researchers at the Australian National University, they told a climatic history that goes back 5.3 million years.

Like in a nature study of the 17th glacier. The result: 5.3 million years of deep sea temperature trends – shown graphically in the picture above – which extend the deep sea record by several million years and indicate that the current Ice Age began 200,000 years earlier than traditionally assumed.

Aside from this finding, the new method could lay a foundation for a more precise understanding of historical climate patterns and their relationship to sea level. With climate change looming, this could prove very useful in our own precarious times.

Layers of sediment in the cliffs of Punta di Maiata, Italy.

Image: Rohling et al./Natur

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