Episode 61: Soft as a Rock: Tectonic Stretching of the Earth's Crust
REPEAT. Geological fieldwork is unlocking details of the creation of the Basin and Range Province in which Tucson sits. The Basin turns out to be an exceptional natural laboratory for studying what happens when the earth's crust undergoes profound hyper-stretching. Hyper-stretching can cause parts of the crust that were buried 10 to 15km deep to be brought to the earth's surface. Ancient rocks are abundant in the sky islands bordering Tucson, in our canyons and mountains, indicating that Southern Arizona was a high elevation plateau before the stretching began. 30 million years ago we could have rafted from a Southern Arizona 'plateau highlands' to what is now Utah! But then, earthquake-by-earthquake, from 25 million years ago to just a moment (5 million years) ago, the plateau sank. This discovery has radically undone the perception that major mountain systems result only from tectonic shortening and buckling of the earth's crust. Today, hyper-stretching like that in our region is happening in Greece, offering a new laboratory for study of this phenomenon in action. In this episode: George Davis, Regents Professor in Geosciences and Provost Emeritus at the U of A; Leslie Tolbert, Ph.D., Regents' Professor in the University of Arizona's Neuroscience Department