"When did Mt. St. Helens last erupt"@en . . "The last eruption of Mt St Helens was on March 8, 2005. This was a small eruption that released a a 36,000-foot (11,000 m) plume of steam and ash."@en . "The last eruption of Mt St Helens was on March 8, 2005. This was a small eruption that released a a 36,000-foot (11,000 m) plume of steam and ash."@en . .