Today not only Catania but also other towns and villages on the slopes of the volcano remain at risk – at least ten such settlements were obliterated in 1669 – and local inhabitants never know when the next eruption may arrive. The most significant recent blast occurred on May 12, 2011, when the authorities had to close Catania airport after a thick layer of ash blanketed its runway. While this was a minor incident compared to the 1669 eruption, it may be a sign of things to come. Mount Etna may yet vent her latent fury on Catania’s population of almost 300,000.
8. Hilo – Mauna Loa
Mauna Loa is an absolute behemoth, the largest volcano on the planet in terms of sheer volume. Even though it has lain quiet, like a sleeping giant, since 1984, danger is still present for those who live in its vicinity. The city of Hilo, home to more than 43,000 people, is actually built on top of old lava flows from the 19th century – so clearly the rivers of molten rock have the capacity to reach it again. Indeed, after an eruption in 1935 planes dropped bombs in the path of lava –which travelled 24 kilometers (15 mi) in just three hours – to divert it away from Hilo. The 1984 eruption also produced fast-moving lava flows that threatened Hilo, stopping just 4 km (2.5 mi) from the city limits.