Waking up is, in the sage words of Sum 41, hard to do. The experience leaves many of us temporarily irritable, such that many of us choose to leave certain loved ones alone until they’ve had time to completely reach a conscious state. Volcanoes are not entirely dissimilar. After lying dormant for decades or more, they can wake up violently—and the best case scenario for people in the vicinity is to get out of their way. But while the alarm clock can give you a good idea of when a human may wake up, a volcano's wake up schedule remains frustratingly and frighteningly cryptic.
Campi Flegrei is a caldera—a collapsed volcanic crater—near Naples, Italy that formed 39,000 years ago in the biggest eruption in Europe’s last 200,000 years. It now sports fields of gaseous vents indicating that the volcano is still alive below the surface. The volcano has been closely monitored—for good reason—and its activity in recent decades has given geologists a lot to study.
In the 1950s, the surface above the caldera began swelling, rising by a total of more than 3 meters since. In 1983 and 1984, its pace quickened, and a flurry of shallow earthquakes and other activity made for a worrying change. That was the end of it, though, and Campi Flegrei slumbered quietly until 2005. Since then, the surface has risen another 0.4 meters, the pace accelerating slowly.