Mount Etna is at it again. The Sicilian volcano has been relatively still for two years, but reawakened this week to put on a spectacular show.

Etna has been active almost continuously for thousands of years, and, as a result of those layers and layers of historic lava flows, it’s the largest and highest volcano in Italy. It is also among the best-studied volcanoes in the world. Historical documentation of eruptions date as far back as 1500 BC; today, it is studied with arrays of high-tech sensors that keep track of earthquakes, emissions, and more.

Eruptions are common but rarely pose a major threat to nearby residents. A million people live within 20 miles of the volcano, where they can get spectacular glimpses of great eruptions in relative safety — even in large eruption lava flows unlikely to reach inhabited areas. However, eruptions of ash can affect air quality and interrupt air travel.

Etna hasn’t seen a major blow-up since 2002. That’s rare — the volcano has seen a large spew at least once a decade since the 1970s. You might say that a large eruption is due, except that volcanos don’t work that way. Unlike earthquakes along a fault, where tension builds and builds until it is released, volcanic activity can wax and wane, and the magmatic plumbing underneath is complicated and not always well understood. Volcanologists deal in forecasts and risk levels, rather than predictions. Even though Etna has put on a fairly good show this week, the risk level remains moderate.

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But putting on a spectacular and safe performance is part of Etna’s appeal. The volcano is a popular spot for tourists hoping to spot some explosive magma with their own eyes. Those who were there Monday night got lucky — the eruptions occurred at night and under clear skies.

Photos via EtnaMiky/YouTube