What led to the eruption of May 1980?

Reader

I assume you are asking about Mount St. Helens. >From the end of March, through April and into May, the north slope of the volcano continued to bulge. After the end of eight weeks, the north slope had bulged a few hundred meters and was very unstable. A large earthquake on the morning of May 18 caused the unstable north slope to collapse as a landslide. That landslide caused an immediate release of pressure on the magma residing beneath the volcano. The reduced pressure caused gas to come out of the magma, and propelled the catastrophic eruption of May 18, 1980.

Sincerely,
John Dvorak

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