“The impact of a Yellowstone eruption is terrifying to comprehend,” says Professor McGuire. “Magma would be flung 50 kilometers into the atmosphere. Within a thousand kilometers virtually all life would be killed by falling ash, lava flows, and the sheer explosive force of the eruption. One thousand cubic kilometers of lava would pour out of the volcano, enough to coat the whole of the USA with a layer 5 inches thick. The explosion would be the loudest noise heard by man for 75,000 years.”