Simplify the following text for a Grade 9 native English-speaking person.
Original: Mount St. Helens showed significant activity on March 8 , 2005 , when a 36000 f plume of steam and ash emergedâ '' visible from Seattle .
Simplified: Mount St. Helens showed important new activity on March 8 , 2005 , when a 36,000-foot ( 11,000 m ) plume of steam and ash came from the volcano .