Zoe Shipton on Geological Cliffs

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"Most people look at a cliff and just see a pile of rocks. But when I look at a cliff I see millions of years of geological time." says Zoe Shipton, Professor of Geology at Strathclyde University. "In cliffs made up of sedimentary rocks, each layer of rock contains clues to how that layer was laid down millions of years ago, and what has happened to it since. We can read those layers like pages in a book". Trying to unpick the geological story of the earth, though, is far from simple - after all "the Earth is nearly 13,000 km across. Geologists are approximately 1.6 m tall, trying to unpick the story of a complicated 4D puzzle - ie one varying in space and changing in time. But we are doing this to decipher the history of a planet that is 100,000,000,000,000,000,000,000 times larger than we are". Undaunted, she takes three cliffs - the Book Cliffs in central Utah, the Grand Canyon and Nanga Parbat in the Himalayas - to explain how geologists decipher the clues left in the rocks. But rocks are subject to the weather, and so to study them in their natural habitat geologists use underground rock laboratories. To extend the depths to which we can observe the Earth even further, geologists use geophysical tools such as seismic surveys. But because we can't produce signals strong enough to penetrate into the very centre of the Earth, geologists use natural signals as well. Listening to earthquakes from the other side of the planet provides information that can be used to map the topography at the outside of the Earth's core. "With modern technology we are learning to read the complete atlas of Earth's history." Written and presented by Zoe Shipton, with readings by David Acton. Additional sound recordings by Chris Watson. Producer: Sarah Blunt