How Do We Know That the Earth's Magnetic Poles Have Flipped? – Christmas Lectures with James Jackson

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Pumice rocks contain small amounts of iron oxide, which is magnetized in the direction of the Earth’s magnetic field as it cools. Comparing rocks of different ages reveals the magnetic history of our planet. Watch Full Lecture Two: James Jackson’s 1995 Christmas Lecture “Planet Earth: An Explorer’s Guide” on the Inner Workings of Planet Earth, Second Lecture. “Secrets of the Depths” from which this clip originated is about the central role of plate tectonics in the structure of our oceans and continents. Watch the full series: Christmas Lectures is a popular children’s science show that airs every year on the BBC. This means that some common features are disabled in this video, such as comments, cards, and endings. The Ri is on Twitter: and Facebook: and Tumblr: Our Editorial Policy: Subscribe to Videos. Latest Science: