18 May, 2010

Happy 30th Anniversary, Mount Saint Helens

30 years ago today, I was a five year-old child watching as reporters somberly announced that Mount St. Helens had blown herself apart. It looked painful, so I made her a get well card. Kids, eh? She was my introduction to the power of volcanoes. Horrifying and enthralling, really, when you live with a volcano rather like her framed in your back window. She's responsible for both my fear and fascination. And she continues to teach me about the vagaries of plate tectonics, the power of subduction zones to create as they destroy, and that one must seize the opportunity to enjoy what's there today because it might blow the hell up tomorrow.

One of the most interesting things about her is that incredible lateral blast that took all the vulcanologists by surprise. In retrospect, it's obvious that enormous bulge in her north flank meant trouble, but at the time, few people realized volcanoes would blow anywhere but up.

Note how distorted her profile had become. She'd gone from America's Fuji to something ominous. Less than a month later, that north face came down, and the mountain blew out. These two videos capture the eruption wonderfully.

And here she stands today, a far different mountain than she had been:

Mount St. Helens, May 14th, 2007
The USGS put together a fantastic report on her past, present and future eruptions, should you like to know more about the science behind her. Join me after the jump if you'd like to take a personal journey with me.

Monday, May 14th, 2007. Almost 27 years to the day since I watched in awe as Mt. St. Helens blew with incomprehensible force, I'm finally visiting the volcano that has haunted most of my life. Nothing has prepared me for seeing a live volcano. My experience to now has been with long-dormant and extinct ones that still managed to dominate my nightmares despite being no threat. But if there's one thing I've always been good at, it's running into the teeth of terror. After all, there's always the option of running away again. And if I panic, or the mountain chooses today to erupt, no problemo. We brought the fast car.

First view of Mount St.Helens, from the main visitor's center. "Thank you for not exploding."

 The author at the Buried A-Frame. As you're driving down Spirit Lake Highway, you'll come across this visceral example of what a lahar can do. The poor owners were only three days from moving in when mudflows from the volcano buried a good part of their house and raised the parking lot by five feet. 

Note to self: do not build home within blast range of active volcano. Especially don't build across the street from a river conveniently situated to channel a lahar straight to my door... 
Toutle River

History: the North Fork of the Toutle River. On May 18th, 1980, this river was a churning mass of super-heated mud. The eruption melted glaciers and snowfields; meltwater mixed with ash, landslide debris, rock, downed trees, and everything else, and roared down the river valley like a volcanic tsunami, obliterating everything in its path. Houses, roads, and bridges vanished under hundreds of feet of boiling hot muddy debris.

Toutle River, May 1980. Courtesy of FAS

You can still see the ravages: while it's a beautiful mountain stream here, there are several places along the way where the banks are fields of ash, and you catch a glimpse of the devastation. In this little spot, just down the street from the A-Frame, you can see log piles and ash banks, and it seems that every stone in the stream is volcanic. The trees are just a patch on the scars. Standing here, with the water rushing and roaring over the rough river bed, warm sun beating down and fine volcanic sands soft against your feet, you can feel echoes of the catastrophe of two and a half decades ago.
Log jams and volcanic ash banks, Toutle River

Driving up the road, very nearly everything's green, luxuriant, and doesn't prepare you for what's to come. The volcano peeks out between the firs. Signs tell you when these forests were planted, some of them quite soon after the 1980 eruption. The whole thing looks very peaceful and lovely. It's hard to believe that it was all a moonscape not so long ago. 

 And then you're entering the blast zone. Trees get shorter, bald hills begin poking through the greenery, and you get a taste of what's to come.

The valley of death. It's hard not to think of Tennyson's poem when you're staring into the throat of an active volcano. From the Johnston Ridge Observatory, you're staring directly into the explosion: the whole north face of St. Helens blew out laterally. Thirty years ago, standing here meant obliteration. Today, it's an unparalleled view.

 You're gazing into the maw of an actively erupting volcano. Mount St. Helens was in continuous eruption from 2004 to 2008, busily building her dome. Those aren't clouds you see inside the crater - that's steam.  But she's probably not going to blow in our faces.  Thanks to USGS geologist John Pallister, who allowed himself to be dropped off in the crater by helicopter to grab some samples from a dome rock the size of the Eiffel Tower as it was emerging, we know that the current eruption is gas-poor.  He compared his samples to bits of lava from 1980 (big boom) and 1983 (dome-building lava flows), and discovered that St. Helens is running out of gas.  Those bizarre solid spines of lava that grew and crumbled sometimes at the rate of 16 feet a day contained just enough gas to push them to the surface before going flat.  Sure, there were a few ash-and-steam eruptions, especially in the first two weeks after she woke up that September in 2004, but it'll be a while before we see anything quite as spectacular as 1980.  She has to fuel up first.

That's not to say the 2004-2008 eruption wasn't fascinating in its own right.  Scientists at the Cascades Volcano Observatory hadn't ever seen anything quite like it: enormous spines the size of skyscrapers grinding their way up to the surface, accompanied by a bizarre, repetitive seismic signature they came to call "drumbeats."  It may not be as visually stunning as a full-blown Plinian eruption, but watch this USGS video and then try telling me it isn't teh awesome:

 "Drumbeat" Seismicity, March 2005, courtesy USGS

Can't do it, can you?

Today, the volcano is fairly quiet, but one look at the parking lot at Johnston Ridge Observatory says all that needs be said about volcanic activity at St. Helens.  Those little burn marks in a practically-new parking lot make me reconsider the wisdom of coming here in the convertible.  On the one hand, fast car = rapid getaway in the event of eruption.  On the other hand, convertible = flammable cloth top.  I can only imagine explaining that one to the insurance company.

A trail loops around the Observatory; there are times when it seems it will lead you straight into the caldera.  Signs abound explaining what to do in the event of an ashfall.  They're silent on what you should do in the event of a blast - perhaps because, if St. Helens decides to erupt in earnest again, there's absolutely nothing that will save you this close in. 
It's the pyroclastic flows, y'see.  She spat out several of them - by one count, a total of 17 - on May 18th, 1980. They roared down the mountain at speeds in excess of 60 miles per hour.  Searing-hot gasses in the ash cloud keep particles suspended, while bigger chunks go along for the ride: the whole behaves like a liquid, flowing in a flood of scalding debris.  Two weeks after the eruption, when geologists could get out there to take readings, the flows were still measuring 570 to 785 degrees Fahrenheit.  Their heat caused  phreatic eruptions where they hit water and caused it to flash to steam.  And least you think those were just little spats, some of them blew ash and steam over a mile high.  This stuff didn't cool fast - a phreatic blast took place just two days shy of the first anniversary of the eruption.  That's some serious heat trapped there.  

Splintered stumps are all that's left of the old growth forest that covered the slopes. It will likely be lifetimes before nature reclaims the blast zone. For now, it's still a desert. On the day of the eruption, old-growth trees blew down, snapped off like twigs by the force of the blastwave. 230 square miles of trees became instant logs.  Nothing clear-cuts like a volcano blowing out laterally. 

For fifteen miles, in the path of the initial blast, trees experienced a cloud of ash and gas traveling at speeds ranging from 220 to 670 miles per hour.  Within five miles of the volcano, where the blast hit hardest, old growth trees on slopes facing St. Helens became nothing more than splinters riding the wave.  Further out, trees lay dead on the ground; the ones sheltered behind ridges still stood, but they were just upright sticks, shorn of branches.  Trees that had survived the blast and the pyroclastic flows were fortunate if they stood on ridges, but the ones in valleys got annihilated by lahars, which either buried them or carried their stripped bodies along to wreak havoc downstream.  Spirit Lake, where it wasn't buried in mudflows, was choked with dead trees. 

Wildlife, needless to say, didn't make it out: everybody there now is an immigrant.  People too close to the volcano or in the path of the mudflows lost their lives as well.  At Johnston Ridge Observatory, a semi-circular granite monument bears their names.  Some of those names were familiar to me after reading Marian T. Place's book about the eruption:

Reid Blackburn, a photographer for the Columbian, who died at Coldwater I when he could have been having a seafood dinner with his bride, Fay.  He was looking for the shot of his career, and might have had it were it not for that lateral blast.

Harry Truman, a feisty old gentleman who lived on the shores of Spirit Lake with dozens of cats and an assortment of memorabilia.  He was buried in one of the many lahars, cats and all, exactly where he wanted to be. 

David Johnston, a geologist for the USGS.  He was directly across from the ominous bulge on the north face, buried under the pyroclastic flow unleashed by the lateral blast.  He had time for one final transmission before he was obliterated: "Vancouver, Vancouver, this is it!"    

Coldwater Ridge overlooks Spirit Lake (and the remnants thereof).  In this place, the three of them are united.  Walking out here, after having spent my young life reading about them, is a deeply moving experience. 

Reid's widow, Fay, said of St. Helens, “To me, she’s beautiful. She hasn’t lost her beauty just because she doesn’t have her cap on. She didn’t mean to kill Reid.”  Standing out here, one doesn't hold grudges.  It's beautiful, serene, and terribly fragile.  What you're boating in today could be so much boiling mud tomorrow.  The forested ridge you're standing on could become an ash field in an instant.  But that's the thrill of volcanic landscapes: their beauty is ephemeral, and change is constant, yet they look eternal. 

On our way out, we pause for a final goodbye.

I'll be back.  And I'm taking special note of the helicopter, there, just in case.

Happy anniversary, love.  


Cujo359 said...

My most vivid memory of that eruption was watching a video produced by a reporter who was trapped in the dust cloud. He was trying to find a safe place until the air cleared up. I was in what was then the Southcenter Mall, perhaps a hundred miles away, when I saw that video. People 100 miles to the east, meanwhile, were trying to get enough dust out of their cars' air cleaners so they could get home.

What Mt. St. Helens taught me is that if you assume you're safe, you're as wrong as the guy who stayed home with his cats when he should have evacuated. That's true no matter where you live. Be as prepared as you can, and make your governments be prepared as well.

Karen said...

There's a book called Volcano Cowboys, by I-forget-who, that provides the inside story on the USGS response to various eruptions including Mt. St. Helens. It's definitely worth a read.

David Johnston knew he was too close, but he took up the observation post anyway. He died for his beloved science.

Alan said...

Very nice article, I really enjoyed reading it. I was born a month before, on Vancouver Island, when St. Helens blew. Mom says the weather got really cold and nasty at the time and have always had a fascination with the eruption since. I hope one day to have a rum and coke over at Spirit Lake and pour one for Mr. Truman and the other victims in remembrance.