When Mt. Saint Helens erupted what was the ecological impact on the area?

Answer 1

it was global
check this site

http://www.olywa.net/radu/valerie/StHelens.html

Answer 2

I was there before and several times after. It was like an atomic bomb went off. Trees were knocked down for miles and everything was covered with ash. Since there is a history of volcanic eruptions, there is no long term impact to the area. It will recover.

Answer 3

From Wikipedia:
"Pyroclastic-flow material passed up the moving avalanche and spread outward, devastating a fan-shaped area 23 miles (37 km) across and 19 miles (30 km) long. In all, about 230 square miles (600 km2) of forest were knocked down within an 8-mile (13 km) inner-fan area, and extreme heat killed trees miles beyond the blow-down zone."

There simply was no ecology in this area after the eruption. Life had to creep back in over a period of years.

"During the nine hours of vigorous eruptive activity, about 540 million tons of ash fell over an area of more than 22,000 mile2 (60,000 km2). "
The total volume of the ash before its compaction by rainfall was about 0.3 mile3 (1.3 km3)."

The ash fall obscured the Sun at midday in Spokane, WA, over 300 miles away. Plants covered by the ash died, as well as animals that inhaled it for any period of time.

Answer 4

Killed almost every thing.