Torgeir Andersen on Ultrahigh-Pressure Metamorphism

<p>Continental crust is buoyant, which is why continents stand high above the ocean floor. Yet rocks in western Norway contain microscopic grains of coesite, a form of quartz that forms only under pressures found about 100 km down. A slab of continent was dragged deep into the mantle, and then came back up. </p><p>In this episode, Torgeir Andersen, Professor Emeritus at the University of Oslo, explains how the rocks of Norway&#39;s Western Gneiss Region made that round trip some 400 million years ago, and why a few isolated diamond-bearing pods may record local overpressure rather than even greater depth.</p><p>For podcast illustrations and to learn more about Geology Bites, go to geologybites.com.</p><p></p>