This was the first flank eruption since 2008–09   On 3 December 2015, an eruption occurred which climaxed between 03:20 and 04:10 local time. The Voragine crater exhibited a lava fountain which reached in height, with an ash plume which reached in height. The activity continued on the following days, with an ash plume that reached in height that forced Catania airport to shut down for a few hours. Volcanic gas emissions from this volcano are measured by a Multi-Component Gas Analyzer System, which detects pre-eruptive degassing of rising magmas, improving prediction of volcanic activity. An eruption on 16 March 2017 injured 10 people, including a BBC News television crew, after magma exploded upon contact with snow. An eruption on 24 December 2018, following a dyke intrusion at shallow depth, spewed ash into the air, forcing the closure of airspace around Mount Etna. Two days later, a magnitude 4.9 earthquake shook the nearby city of Catania, damaging buildings and injuring four people. The Global Volcanism Program has assigned a volcanic explosivity index (VEI) to all of Mount Etna's eruptions since January 1955:  In the 1970s Etna erupted smoke rings, one of the first captured events of this type, which are extremely rare. This happened again in 2000. Video footage of 8 June 2000 event was captured by naturalist filmmaker Geoff Mackley. Another event occurred on 11 April 2013. The borders of ten municipalities (Adrano, Biancavilla, Belpasso, Bronte (from two sides), Castiglione di Sicilia, Maletto, Nicolosi, Randazzo, Sant'Alfio, Zafferana Etnea) meet on the summit of Mount Etna, making this point one of elevenfold complexity. Etna is one of Sicily's main tourist attractions, with thousands of visitors every year. The most common route is through the road leading to Sapienza Refuge ski area, lying at the south of the crater at elevation of 1910 m. From the Refuge, a cableway runs uphill to an elevation of 2500 m, from where the crater area at 2920 m is accessible. Ferrovia Circumetnea – Round-Etna railway – is a narrow-gauge railway constructed between 1889 and 1895. It runs around the volcano in a 110-km long semi-circle starting in Catania and ending in Riposto 28 km north of Catania.