The three volcanoes ( most notably Arsia Mons ) also all have collapse features and rifts, from which flank eruptions issued, that transect them along the same northeast-southwest trend.
12.
A 1922 eruption on the southwestern flank produced a lava flow that reached the Atlantic coast, and a lava flow from a 1999 south-flank eruption stopped only 200 m ( 660 ft ) from the sea, cutting the coastal highway.
13.
The eruption continued at a slowly diminishing rate for 417 days, until 6 July 2009, making this the longest flank eruption of Etna since the 1991 1993 eruption that lasted 473 days . Previous eruptions, in 2001, 2002 2003, and 2004 2005 had lasted 3 weeks, 3 months, and 6 months, respectively.
