ROME—Mount Etna has roared back to spectacular action after a few months of relative quiet, sending up a 7.5-mile high volcanic ash cloud over eastern Sicily. The lava flow from Etna, one of Europe’s most active volcanoes, was centered around the crater on the mountain’s southeast slope, Italy’s National Institute of Geophysics and Vulcanology said Monday. There were no immediate reports of injuries or property damage on the inhabited towns ringing the slopes of the volcano, which is popular with hikers, skiers, and other tourists. By Monday afternoon, the lava flow from the crater had stopped, the institute said. But earlier in the day, while the volcanic cloud was pouring out of Etna, the institute issued a warning for aircraft in the area. The towering cloud, visible for kilometers, was the latest impressive show of Etna’s power this month. Earlier in February, a particularly powerful eruption sent bolts of lightning …