Mount Etna, Europe's most active volcano, erupted on Monday, sending a large cloud of smoke and ash high into the air. Catania airport was put on alert, but flights were not immediately affected, and the ash cloud stopped by the afternoon. The eruption happened because part of the southeast crater fell in, creating hot lava flows, but it didn't put nearby people in danger. The top of Mount Etna was closed to tourists as a safety measure, but the lava stayed in its natural area. People in nearby towns and villages felt the eruption, and it caused a lot of discussion on social media. Even with the disruption, Etna is still a popular place for tourists because it is very tall and has a large surface area.