This week, we’re looking at the explosive geology of volcanoes, and how they shape our world both physically and politically. We’ll speak to climate researcher Nicholas Klingaman, about his book The Year Without Summer: 1816 and the Volcano That Darkened the World and Changed History. And we’re joined by geologist Jacob Lowenstern, Scientist-in-Charge of the Yellowstone Volcano Observatory, about the massive volcano that drives the geologic activity of the Yellowstone Caldera.