We know very little about the processes that lead to a reeruption of supervolcanoes such as the mostly underwater Kikai caldera in Japan (pictured) and are therefore ill-equipped to make predictions. Credit: Nobukazu Seama Scientists have discovered that the magma reservoir tied to the largest volcanic eruption of the Holocene is filling again. The finding, led by Kobe University researchers studying Japan's Kikai caldera, offers new insight into how massive caldera systems such as Yellowstone