evidence: A crackling burst cut through the air on June 17, 1923, as Mount Etna—one of the world’s most active volcanoes—unleashed a mighty eruption. After burbling and shaking that fateful day, the peak convulsed, emitting an uproar like "the discharge of a thousand massed guns," according to a dispatch from Rome to the Australian Mercury newspaper the next day. [...] While this eruption—and most others at Etna since—haven’t caused many deaths, the volcano is capable of intense destruction. During Etna’s most damaging eruption, in 1669, lava flowed from the peak for months, stretching more than ten miles away and entombing villages and fields that lay in its path. [...] No matter the magmatic source, Etna’s recent explosive vim and vigor—with more paroxysms in the last 25 years than the preceding 300—has made one thing clear: The volcano has much more firepower in store. "The activity at the moment is absolutely huge," Murray says. "And it looks as if the eruption rate is still going to climb."