Mount Etna, Europe’s most active volcano, erupted on Sunday, spewing ash on Catania, eastern Sicily’s largest city, and forcing a shutdown of the city’s airport.Italy’s National Institute of Geophysics and Volcanology, which closely monitors Etna with instrumentation on the slopes, noted that cloud cover on a rainy day was impeding views of the eruption, which often serves up a spectacular display of flaming lava during the volcano’s not infrequent eruptions.AP