Mount St. Helens in southwestern Washington state appears to sit quietly. Its horseshoe-shaped crater curves gently, as if to embrace the countryside below it. But don’t be fooled. Scientists say there’s action going on underfoot.
Since the beginning of 2016, seismographs have picked up activity. From two to seven kilometers below the Earth’s surface, small earthquakes rumble, one closely followed by another. Geologists call these “earthquake swarms.” They’re a sign that St. Helens is not truly dormant. Down deep, melted rock is likely flowing into open spaces inside the mountain. The volcano is recharging its magma stores.
Once, Mount St. Helens was a picturesque pointed cone rising above the timbered terrain. Locals called it the “Mount Fuji of America.” But on May 18, 1980, the volcano blew its top—literally. A full 1,300 feet of mountaintop exploded when the eruption happened. It blew outward and crumbled away in the following avalanche. Over time, multiple smaller eruptions have formed a lava dome inside the remaining crater. Ice now covers it again. The blackened base of the mountain is slowly being renewed with green as vegetative life creeps back up it.
But the rumblings beneath the decapitated mountain suggest that recovery may be interrupted in the future. So volcanologists monitor the volcano constantly. They say another eruption is almost certain—but will it measure up to the catastrophic event of 1980?
In March of 1980, young volcanologist David Johnston was studying Mount St. Helens from a ridge six miles north. After several small earthquake swarms, Johnston saw fissures in the ice at the summit. Over the next two days, two craters opened near the top. Steam gushed from the craters, which merged together into one large hole at the end of March.
Johnston warned the United States Geological Survey (USGS) headquarters in Vancouver. The USGS encouraged residents, campers, visitors, and timber companies to evacuate the area for miles around the mountain. Most people heeded the warnings and moved to safety. Johnston stayed, fully knowing the risk to his life. On May 18, he radioed Vancouver as a 5.1 magnitude earthquake hit: “This is it! This is it!”
Moments later, the north side of Mount St. Helens ruptured. A lateral blast of hot air obliterated everything in its path for six full miles—including the station where Johnston worked. For another six miles out, every tree was laid flat. The blast was the most devastating volcanic eruption in U.S. history, destroying 250 homes and claiming 57 lives.
