Mount Etna, by far the largest of Italy’s three active volcanoes, has erupted spectacularly overnight, sending a fountain of lava rocketing 1 kilometer (0.6 miles) into the sky, accompanied by both a tremendous, 3-kilometer-high (1.9 miles) ash plume and iridescent, volcanic lightning.
Although this eruption was relatively short lived, it marks the first time that the fiery mountain, sometimes called the Roof of the Mediterranean, has erupted in this way for almost two years.
Lava bubbles and broils at the Voragine crater. Marco Restivo/Demotix/Corbis
The Voragine crater of the Sicilian stratovolcano, a vast edifice 3,329 meters (10,922 feet) high and covering an area of 1,190 square kilometers (459 square miles), burst into life last night. By this morning, the mountain had calmed down, with only a small, white plume of ash effusing from the crater. Although lava had been oozing sporadically from this crater all year, most of the volcanic activity was centered on the New Southeast Crater.
Inarguably, the most spectacular feature of last night’s eruption was the volcanic lightning that seemed to emanate from the dark plume of ash. Although not particularly rare, it is a highly unpredictable phenomenon that is difficult to capture on camera. There is some debate as to what causes it, but most volcanologists think that it’s something to do with the positive charge much of the fresh ejecta has when it’s launched skywards.
Incredible timelapse of Mount #Etna's eruption last night, first in 2 years. https://t.co/RGzlQVjHSz pic.twitter.com/l456OF1Njh
— Alejandro Alvarez (@aletweetsnews) December 4, 2015
As the sky begins to build up a region of positively charged debris, a zone of negative charge forms behind it. A lightning strike from the sky downwards is nature’s way of sorting out this charge imbalance. This, however, is only one type of volcanic lightning: some emerges from the volcanic vent itself as lava spews out of it. The second type is far more mysterious, and scientists still cannot be sure how it forms, although it is likely due to particles impacting each other, causing some to become highly charged.
Overnight eruption of Mount #Etna, from MSG Infrared @eumetsat_users pic.twitter.com/6ceHDpIPid
— Dan Lindsey (@DanLindsey77) December 3, 2015
The area around the crater has been somewhat restless for the last few weeks, with small, explosive slugs of gas breaching the volcanic vent. These little slugs of gas, formed when thousands of smaller gas bubbles coalesce within the magma making its way to the surface, fling blobs and bombs of lava into the sky, which then spatter down across the landscape. This type of mildly explosive activity is called “Strombolian,” named after another Sicilian volcano that incidentally inspired Tolkien’s Mount Doom in the "Lord of the Rings" books.
This activity, while rather beautiful to look at, isn’t dangerous – although as a precautionary measure, the nearest airport was shut down. Mount Etna has been erupting on and off for around 2.5 million years, its source magma being forced up from the depths by the complex collision of the Eurasian and African tectonic plates. Even during its calmer times, its vast magma supply is never too far from the surface; any piece of wood or paper that is left resting on the otherworldly surface will rapidly ignite and burst into flames.