"Beginning in mid-March 1980, a series of earth tremors and steam explosions at Washington's Mount Saint Helens suggested that the volcano—dormant since 1857—was on the verge of erupting. Then, on May 18, the entire north side of the mountain exploded in a cloud of ash, rock, and fiery gases that collapsed a good part of it and carried debris for many miles. About 60 people were killed, and millions of tons of ash blanketed much of the American northwest. How far did the ash eventually spread?"