Mt. St. Helens Top of Volcano Blown Off In Blast! 18/04/82. 60 people were killed today when Mt. St Helens blew its top Mt. St Helens erupted two years ago today in a blast that caused the volcano to be reduced by 451 metres (1313 feet). The volcano is south-western Washington and is part of the Cascade Range. Mt. St Helens had been dormant since 1859 and has let off its first blast since then today. The volcano killed all life in an area of 180 sq. cm(70 sq. miles) including at least 60 people! The ash and dust spread much farther than this, of course. Today it is continuing to emit to emit dust and ash at intervals.