In fact, in the past half-millennium, Mount St. Helens has erupted on multiple occasions. Most of these incidents came with little fanfare, however. And between 1857 and the late 20th century, the stratovolcano even sat entirely inactive – until the year 1980, that is, when the enormous peak came back to life with a vengeance.
Seismographs began detecting activity around Mount St. Helens in mid-March of that year. Said small quakes suggested that magma may have been starting to shift beneath its surface once again. And sure enough, on March 20 a 4.2-magnitude earthquake on Mount St. Helens’ north side confirmed suspicions that the volcano had indeed awoken from its slumber.
For the next several weeks, those in the Seattle area watched as Mount St. Helens’ warnings grew more and more aggressive. On March 27, for instance, heat from underlying magma created violent blasts of steam – the result of groundwater that had suddenly spiked in temperature. And the power of these explosions formed a 250-foot crater and sent ash flying 7,000 feet into the air.