The most explosive volcanic eruptions are striking not just for their vivid pyrotechnic displays, or for the huge clouds of ash they spew into the air. Often, the aftermath is just as jarring—the miles upon miles of ash that blanket the earth, extinguishing the life that grew there and suppressing any that was to come. But nothing is forever. Take Mount St. Helens, whose gargantuan eruption 40 years ago—the deadliest in U.S. history—completely destroyed the top of the mountain. An earthquake first jolted the volcano into activity, causing the largest…
