Do you need book suggestions for that person-interested-in-geology? Do you need to know what to get people in order to turn them into rock fanatics? I’ve got ye covered over at Rosetta Stones! Enjoy, my darlings.
Dec 12 2013
Ah, winter. Ah, week-of-sub-zero-temperatures. You know, we’re used to chill in Seattle, but we’re not used to day after day after day after etc. of freezing cold. The moderating influence of the nearby ocean generally keeps us from being uber-icy. But then comes a cold snap, and it seems like the whole place freezes solid.
But the neat thing is, in places, our wet ground stays sorta warm, while the air is sub-freezing. And magic happens. Needle ice!
There it was, rearing out of the ground, tall and bold after having grown for several days. This is up against one of the buildings, at the edge of the lawn, under the rhodies, where the ground has a chance to stay warm and this stuff’s reasonably protected.
Dec 11 2013
A few seconds after the beginning of the directed blast, life within roughly ten kilometers (6.2 miles) of Mount St. Helens within the blast zone was about to be extinguished.
“Directed blasts,” Rick Hoblitt, Dan Miller, and James Vallance wrote in their 1981 paper on the blast deposits, “typically devastate large areas… and kill essentially all above-ground life within these areas.” Human and animal, arthropod and avian, tree, bush and flower, all perished. Between its kinetic and heat energy, the directed blast released the equivalent of 24 megatons of energy in a few short moments. This is one megaton short of the theoretical yield of the largest hydrogen bombs the United States ever created; the first nuclear bombs to destroy a city were only 15 and 21 kilotons, respectively – orders of magnitude smaller. Instruments measuring the blast saw “amplitude variations comparable to those caused by detonation of nuclear devices in the 1-10 mt [megaton] range.”
Dec 10 2013
I was going to save this photo for when I’d had time to go back through my recording of the ranger talk and recall what it was the ranger said about it – iron staining? Bacteria? They don’t know? But some of you wanted a larger image of Mount St. Helens’s lovely red waterfall, and so a larger image you shall have right now. Because I love you:
And because I love you very, very much, thee shall have an image of the red waterfall with Mount Adams peeking over it.
Eventually, I’ll have a whole big missive about that red waterfall prepared for you. Eventually.
Dec 09 2013
The cryptodome growing within Mount St. Helens sowed the seeds of its own destruction. Had it been a small thing, it might have become a younger sibling to Goat Rocks. Pacific Northwesterners might have seen a few displays of volcanic fireworks, another dome added to the edifice, and a return to serenity. It hardly would have made the news.
But this dome, unlike Goat Rocks, kept growing, there beneath the surface. It set groundwater steaming. The hydrothermal system driven by its heat caused some pretty spectacular phreatic eruptions. It severely over-steepened the volcano’s north flank.
And it kept growing, right up until the end, when an earthquake on the morning of May 18th, 1980, brought the whole thing down.
This is a story of seconds. A lot can happen in a few seconds. A whole mountain can change.
Before 8:32:11 am Pacific Daylight Time, the cryptodome had been following the usual trajectory of masses of magma hanging about under a volcano’s skin. The hot dacite was cooling down toward the point where liquids become solids. Various minerals were crystallizing as the magma cooled; toward the outside, where fresh dacite met old volcanic products and water circulated through the hydrothermal system, things had cooled a bit more than in the interior, and probably formed something of a dense crust with only minor, if any, vesicles. Other bits of the dome might have been a little more bubbly, with gasses forming more vesicles than at the relatively solid outer edges. But everything was under pressure – 175 bars of it – and so most gasses would have been dissolved within the melt. Even the water heated by the magma hadn’t boiled. Under that much pressure, it couldn’t get steamy.
This all sounds very quiet and happy, but gasses, including water vapor, that are under pressure are being forcibly confined to a small volume. They’re the kind of things that normally take up quite a bit of space. Give them an opportunity, and they’ll proceed to do so rather emphatically.
Opportunity rang at 8:32:11 am PDT in the form of a magnitude 5.1 earthquake. It took about ten seconds for the unstable north face to begin sliding. Old rock, debris, domes, dirt, and glaciers careened down the mountainside, leaving a scarp 700 meters (2,297 feet) high, 1 kilometer (3,281 feet) wide, and just 20° off from vertical. All of that stuff had been keeping the lid on the cryptodome and its hydrothermal system. Now the pressure was off. And all of those gasses that had been kept down were now free to get out.
They didn’t go immediately. It took almost twenty seconds for the blast to begin after all that volatile material found itself freed. It’s possible the cryptodome and its hydrothermal system weren’t yet completely exposed, and expanding gasses might have been working their way through the remains of the north flank towards freedom. But there are also some complicated fluid dynamics to contend with. Even if the cryptodome had been instantly not-crypto, the blast would have taken some time – upwards of at least ten seconds – to form. A rarefaction (expansion) wave had to propagate, water needed to flash to steam, and dissolved gasses begin exsolving (coming out of solution), before an expansion wave involving more than one phase got round to propelling vapor and bits of volcano out.
This is all a complicated (yet greatly simplified) way of saying: water flashing to steam and gasses released from confinement blew the cryptodome apart.
There’s still some debate over whether the magmatic gasses within the cryptodome or the steam in the hydrothermal system caused the blast. The fact that so much of the dacite cryptodome got blown out suggests that its own gasses were major contributors. Regardless of which set of volatiles got things moving, once steam, magmatic gasses, bits of dome, and appreciable chunks of Mount St. Helens not stripped off by the landslide blasted through the base of the landslide scarp while more erupted from the top. Mind you, the landslide scarp wasn’t an immobile feature: it was slip-sliding down as block #2, leaving plenty of room for the expanding gasses to escape – sideways.
This is not usual behavior at volcanoes. But gasses that have been confined to a small space want to be in a large one, and they are not big on protocol. If a landslide leaves an exit in the side of a mountain, a lateral blast is the way they’ll go. Things were merely sonic to begin with, but as the blast reached the open air, it expanded supersonically. Fragments of old rock, hot chunks of the dome, and debris picked up on the way formed a roiling, boiling, dark gray cloud. Going up, gravity worked against it; going down, what was left of the ground interfered – but laterally, it found its way clear. It expanded more than 90° around the vent and sped down the mountain at speeds exceeding 600 km/h (373mph). In the valleys of the North and South forks of the Toutle River, the atmosphere was about to decide the fate of people who had, only seconds before, been enjoying a beautiful May morning.
Lipman, Peter W., and Mullineaux, Donal R., Editors (1981): The 1980 Eruptions of Mount St. Helens, Washington. U.S. Geological Survey Professional Paper 1250.
Special thanks to Helena Mallonee of Liberty, Equality, and Geology for use of her photo; and Lockwood DeWitt of Outside the Interzone for an excellent description of what the gasses were up to before and during the blast.
Previously published at Scientific American/Rosetta Stones.
Dec 08 2013
So last week saw us treated to Elan Gale’s made-up saga, in which a woman annoyed people and he, Bwave Hewo, descended from the dizzying heights of being responsible for shit-sandwich television such as The Bachelor and proceeded to demonstrate how he believes that bullying sick women will make our social ills go away. Also, he seemed to have some idea he was doing the staff being bawled out by his imaginary woman a favor.
This is wrong on so very many levels.
Firstly: The fact he did this as a little light entertainment/publicity stunt on a holiday weekend shows he’s a first-rate shithead – as if we couldn’t already guess that from his teevee programs.
Secondly, as a thought problem, it sends the message that in these situations, asshole behavior + even more asshole behavior = harmony. This math does not work in the world outside Mr. Gale’s head.
Thirdly, Mr. Gale has set a terrible example for his followers, who now believe it’s heroic to be a misogynistic asshole to random women in unflattering pants and medical masks. His situation may be fiction, but life often imitates art (or piss-poor versions thereof), and we humans do take lessons and morals from stories. So do expect an uptick in asshole behavior from onlookers in all sorts of tense situations, plus much tweeting about what Bwave, Bwave Hewoes they are. Thanks to you, Mr. Gale, the world has just become that much more measurably worse.
Fourthly, even his stated objective fails: he claims to want to make things better by punishing a woman for being an asshole to staff. And I’m sure most of us agree that it would be nice not to reward assholes. However, as a person who has worked in all manner of retail, customer service, and technical support fields, I can tell you that having one asshole customer poked and prodded and annoyed by another asshole customer only makes the situation far worse for the poor staff member caught in the shit-flinging. More shit is sailing, and the original asshole now has a hemorrhoid. How happy is your asshole when it’s got one of those? How much more miserable does it make you? Yeah.
Put it like this: if I were a zookeeper being harassed by a rather irritated tiger at feeding time, the last damn thing I need is some dumbshit in the audience deciding that what would really help the situation is to start pelting it with rocks. One or both of us is likely to get mauled, the poor tiger will feel completely justified as well as infinitely put out, and there’s no way the situation’s going to end happily for anyone except those who like their visits to the zoo to include bloody chunks of flesh being flung every which way.
So, fans of the Elan Gale method of making service people’s lives better: don’t. Just don’t. Sit down, shut the fuck up, and let the professional (helpful hint: this is not you) handle the situation. If this isn’t exciting enough for you, please go find a therapist who can explore the reasons why you may be such a terrible person and help you modify your behavior to become less of one.
And if you really want to help? Try gently defusing the original asshole. Or wait until that asshole has departed, and give the staff member some sympathy.
Now let us have some songs that rather perfectly describe Mr. Gale and his ilk.
Dec 07 2013
A serene terror loomed outside my schoolroom windows.
I went to school at the foot of a mountain made of dacite, the same kind of magma that blew Mount St. Helens apart. If I’d known that then, I probably would have had to change schools. I’d seen the eruption on television and read about the destruction in Marian T. Place’s excellent book. I already spent an inordinate amount of classroom time watching Elden for the slightest sign of steam, and that was back when I thought it was a shield volcano and the school would merely be buried in streams of red flowing lava, just like unfortunate structures in Iceland or Hawaii. I’d probably have come undone if I’d thought it would explode. I had a volcano phobia.
Dec 05 2013
Part V of our Mount St. Helens field trip guide is up. Go for the views, stay for the super-awesome topo maps with lights showing various bits of the eruption!
Dec 04 2013
One of the most surprising aspects of the May 18th eruption of Mount St. Helens was the devastating lateral blast that ravaged such a large area. We’ll be spending the next few posts on that subject. It’s a complicated aspect of a very complex eruption, so before we dive in, let’s have a look at historic lateral blasts, what we knew before the whole side of Mount St. Helens blew out, and some of what we learned from her.
Lateral blasts weren’t completely unknown before 1980. In 1888, Bandai-san in Japan experienced a catastrophic eruption that removed 1.5 cubic kilometers (.36 cubic miles) of its summit. Its former Fuji-like summit was reduced to a shattered remnant – much like another volcano we’ve become intimate with. Imperial University of Tokyo geologists Seikei Sekiya and Y. Kikuchi thought the deposits left at base of Bandai-san’s north slope were the result of a landslide; Soviet volcanologist G. S. Gorshkov put them down to a directed blast. Could it have been both? Mount St. Helens tipped us off to the possibility that such blasts were very much related to landsliding: an earthquake knocks an unstable slope loose, the resulting landslide depressurizes a magma chamber (and/or hydrothermal system?) beneath, and boom.
Dec 03 2013
Aw, yeah, it’s the return of the UFDs! I’ve been extremely lax. Also, the birds were buggers this summer. So I’m reaching into the past for a few likely candidates.
I’ll start us easy, with some serene little water birds. I quite like these. They’re tiny, and they’ve got that pretty green streak in their wings.
I see these round here a lot. I suspect I know what they are, and they’ve got to be dead easy, but they’re cute, so why not?
These little delights were at a pond on North Creek last winter, along with about ten billion other water birds. They don’t seem to mind ice a bit.
Right. There’s a little something for ye. Let me know what we’ve got!