A glass jar sits on my shelf amongst other relics. I know precisely how old the contents are: 39 years old today.

On May 18, 1980, triggered by an earthquake, the side of Mt. St Helens collapsed in a landslide–the largest ever recorded.  The magma that had been building below over several months, causing a huge bulge on the north face, suddenly exploded both sideways and up–15 miles up– at the same time. Ash–like the ash in my jar–would be deposited in 11 US states and two Canadian provinces

The eruption was not unexpected. The mountain, silent since the last century, had awakened with earthquakes and vents of steam, and the gradual building of pressure on the north face.  Residents had been warned to evacuate; most had, but Harry Truman, an elderly man who kept an inn on the shores of formerly-pristine Spirit Lake, had refused, and was one of 57 people directly killed by the eruption.  Another was US Geological Services volcanologist David Johnston.  His last words, “Vancouver! Vancouver! This is it! This is it!” as he watched the eruption unfold from a ridge six miles away, were conveyed via radio before the rapidly-moving blast overwhelmed him.  His body was never found, but the ridge where his camp was situated was renamed in his honour.

The eruption of Mt. St. Helens was the most deadly volcanic eruption in recorded history in the continental United States, but its Volcanic Explosivity Index rating was only a 4, ejecting .25 cubic kilometres of material, similar to that of Eyjafjallajökull in Iceland in 2010. Each step of the VEI increases in intensity approximately tenfold The eruption of Vesuvius in 79 AD had a VEI of 5, ejecting 3.3 cubic kilometres–but compare that to that of Toba, with its VEI of 8, which ejected 2800 cubic kilometres of debris.   It was what is known as a Plinian eruption–that is, the same type of eruption as Vesuvius in 79 AD, as described by Pliny the Younger. Such eruptions include an ash cloud that reaches the stratosphere, and may generate pyroclastic flows.  St. Helens certainly did, as lava melted snow and earth into huge surges of boiling mud and debris that clogged the Toutle River.  Over a billion dollars in damages was caused by the eruption, most by the floods and mudslides, but also due to the effects of the ash, which clogged machinery.

The sideways eruption of St. Helens was particularly unusual, being described as similar to that of popping the top off of a champagne bottle turned sideways. The mountain was reduced in height by over 1300 feet, and the once near-perfect cone was replaced by a massive, lopsided crater as the mountain collapsed into the emptied magma chamber. The resulting blast zone was described as a moonscape by visiting President Jimmy Carter, who toured the area not long after. Spirit Lake had completely disappeared, and geologists searching for landmarks were quickly confused.

Thirty-nine years later, however, Spirit Lake is back–shallower than it was, but teeming with life.  The pioneer plants of the early years after the eruption gradually began to give way to trees.  Still, some areas close to the mountain are still quite devastated.  St. Helens has erupted as recently as 11 years ago, and is still considered active.  It’s now part of a national park, and continuously monitored.

Slideshow of before and after photos

The eruption of Mt. St. Helens has particular resonance for me, not only because I remember it, but because I wrote my very first high school term paper on it.  This is where I began to understand how to put together a longer researched essay and how to look at a variety of different sources to be able to tell a story.  Hopefully someday I’ll get to see the mountain in person.

The jar of ash?  Oddly enough, it came from a garage sale.  The label is hand lettered, in masking tape, with the date it was collected–July, 1980.  How that came to be found in a garage sale in suburban Columbus a few years later shall remain a mystery.