Happy Birthday !
Twenty-five years ago on May 18, Mt. St. Helens exploded. When the mountain first came to back to life in mid-March of 1980, I was certain it would erupt. Then, as the mechanics of geology progressed, we saw things that many had guessed would happen and some that were so surprising, not even the geologists guessed they would happen. A short list includes: The growing bulge on the north flank of the mountain; The small almost slight earthquakes that were occurring daily; The overwhelming explosion and the globe encircling ash cloud.
Never had such an eruption been recorded although ancient stories come through in legends of local native peoples. Almost every one involved expected a lava type eruption, where the mountain would open and begin to spew lava, much like we are used to seeing with the Hawaiian volcanos. But the growing bulge had not been previously seen or experienced. While the newly described Harmonic tremors were unknown, they were properly diagnosed as lava moving deep within the mountain. No one could be sure what that really meant. However, in the moments following a 5.1 earthquake, we found out. The huge extended bulge collapsed and slid from the mountain into Spirit Lake. The released sulfur dioxide gas blew the top twelve hundred feet of Mt. St. Helens forty thousand feet into the skies. And the impact woke me from a sound sleep.
We at that time lived in eastern Washington, a hundred miles and more from Mt. St. Helens, and yet in just a few minutes the sound of that explosion shook the house and brought me out of bed looking for thunder clouds. Then a couple of hours later the ash began to fall. The sky turned yellow and the clouds took on the appearance of giant polyps, heavy and sagging. The ashfall brought most of Eastern Washington to a halt. The interstate was shut down as well as towns and cities across the area. Street lights came on in the middle of the day and visibility dropped to fractions of a mile.
We were told that the explosion had the force of nineteen atomic bombs. I guess that is as good a way to describe the force and resulting devastation. I personally believe that it distracts from the true forces involved, but, We Modern People, find it easier to correlate such an abstract power. One of the things that was never seen before was the pyroclastic flow that was simultaneously unleashed with that explosion. The sudden expansion of all that gas rushed northward and flattened over three hundred square miles of timber. I mean timber! Logs three feet in diameter, trees a hundred feet tall, were laid flat in a blink. Their needles and branches vaporized and carried with the gas cloud. For thirteen miles from the crater huge trees were laid flat in the direction of the blast. Yup, it was quite the thing.
The lahar (mudflow)* that swept down the Toutle River destroyed everything in its path and filled the Columbia River with debris and ash. When the area was opened to visitors the following year, we went to see what happened. Nothing was growing. The only trees standing were on the leeward side of ridges and even they had been stripped of leaves and branches. The whole area was gray and barren. It was a monochromatic landscape covered in ash, void of everything, except for devastation.
Never, before had such a thing actually been witnessed and since studied. There have been many other surprises since that eruption. The regeneration of the forest, the return of animal life, including insects and fish. The ash is still there, now compacted down and still that grainy gray color. Yes time has moved on and some things that since happened were expected. For one, the rebuilding of the mountain with a new lava dome and general quiet of those things that led to the initial eruption. Then last fall events started to happen again.
There is something that most people, even here in the northwest, aren't aware of. The biggest is that Mt. St. Helens has been in a continual state of eruption since October 6 of 04. Yup. There is a new lava dome that is even now growing at a rate of six inches a day. The amount of lava being extruded from the mountain has been portrayed as the equivalent of the volume of a swimming pool per minute! This is a study in geology, of the mechanics that govern our planet. What will happen next? I don't know. It will be curious to see and interesting to live through. So let the celebration begin.
If you are at all curious about this active volcano and would like to learn more-click here-
|* A lahar is a mudflow made up of ash and water, usually melted snow
or glaciers, that is sent down a river or canyon at high speeds. They
are actually quite common and the west slope of Mount Rainer spreading
out toward Tacoma and Olympia is layered with them.
*Also called debris flows
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