Dormant volcanoes are those with a history of activity but currently show no signs of erupting. They are like a ticking time bomb. Because they don’t erupt frequently, people often settle on their fertile slopes, forgetting the danger. Mount Vesuvius, which destroyed Pompeii, was dormant for a long period before its catastrophic eruption in 79 AD. Geologists monitor these sites for “ground deformation” or “micro-earthquakes,” which indicate that magma is moving back into the chamber and the “sleeping” giant might be getting ready to wake up.