My Carpet: A Fable

Your carpet is old and disgusting. It’s worn and torn, stained and strained. It’s filled with the remains of hairball-hurfing episodes, and smells distressingly of elderly cat urine. Babies break out in a dermatologist-defying rash whenever they crawl over it. The miasma arising from it may be causing a new sort of breathing disorder. Its indeterminate orangey-gray hue with the super-villain-creating toxic-sludge colored spots drains your happiness right out, and is probably contributing to your family’s assorted mood disorders.

“Aftermath” by A National Acrobat on Flickr

But you shouldn’t replace it. Nossir. Yes, you are suffering; yes, you could buy a new carpet and a college education with the money you are spending on doctor’s bills and air fresheners. But a person must have principles. It’s very silly and selfish of you to want a new carpet when there are people in other countries who endure the agony of living on dirt floors. No new carpet for you until everyone in the world has a carpet!

How dare you complain about what the dog did to the carpet while you were away when some people don’t even have a dog, much less a carpet?!

You are a terrible, selfish person, and every decent person should shun you. You are diluting the meaning of carpet-deprivation. You should be ashamed.

Please excuse me now – there’s a sale on carpet at Home Depot, and I’ve got to go. Well, of course, I won’t tolerate the occasional stain on my own carpet, and that color is so last year. What, why are you calling me a hypocrite? I don’t complain to the world about how awful my carpet is!

 

(Inspired by this bit o’ nonsense, which stands in for all of the “Dear Muslima” and “But there are starving children in Africa!” nonsense.)

Prelude to a Catastrophe: “Something Dramatic”

The earthquake activity at Mount St. Helens had built to a crescendo. When a volcano shakes this hard, it almost always spells trouble: magma rising, an eruption imminent. You can’t know exactly what they are going to do, and when, and to what degree. But you suspect. You prepare as best you can.

On March 27th, the USGS issued a Hazards Watch, informing public officials of the dangers St. Helens might pose. After a week of increasing shakes, there was little doubt in any scientist’s mind that “something dramatic” was about to happen. By 11:20am Pacific Standard Time, something dramatic had.

Summit area of Mount St. Helens. Aerial view on the afternoon of March 27 looking east, showing newly formed crater, swath of dark new ash mainly to southeast of new crater, an east-west fault across middle of summit area, and an uplift or bulge on upper north flank of the volcano. Photo by David Frank. Skamania County, Washington. March 27, 1980. Portion of Figure 6, U.S. Geological Survey Professional paper 1250.

Summit area of Mount St. Helens. Aerial view on the afternoon of March 27 looking east, showing newly formed crater, swath of dark new ash mainly to southeast of new crater, an east-west fault across middle of summit area, and an uplift or bulge on upper north flank of the volcano. Photo by David Frank. Skamania County, Washington. March 27, 1980. Portion of Figure 6, U.S. Geological Survey Professional paper 1250.

It must have been eerie for the observer in the Army National Guard plane who first saw the gaping hole in her formerly-pristine summit. A dark gray streak of ash stained the snow, following the winds to the southeast. The deep snow had cracked. She was awake. And it wouldn’t be long before she let folks know she was feeling feisty.

At 12:36pm, a boom echoed through the wilderness near the volcano. Portland reporter Mike Beard, flying above her, saw ash roiling “like smoke out of a chimney” through the clouds.

Phreatic explosion from Mount St. Helens. This image is from a later eruption, but is similar to what Mike Beard would have seen on March 27th. USGS photo courtesy of Dan Miller.

When volcanoes erupt, many people think lava. Lots of lava. And that is true for some volcanoes, like the lovely shields that make Hawaii such an interesting place to live. But a volcano like St. Helens doesn’t start with lava. She begins by clearing her throat, so to speak, gargling a bit, putting on a small performance before the main event. In her case, thick, sticky dacite, a type of magma rather rich in silica, was making its laborious way up toward the surface. Dacite has a tendency to form domes. It also has a distressing tendency to blow up. But the rising dacite hadn’t reached the surface just yet: it had just gotten close enough that its heat flashed water to steam. The result was a phreatic (steam) eruption, strong enough to break and pulverize summit rock and blow a hole in the top. Steam and ash gave Mike Beard a jolly good show, and made a racket. But no lava. Not yet.

Still. The phreatic eruptions caused some pretty dramatic changes.

Oblique aerial photographs of the Mount St. Helens summit area showing historic thermal areas. Distance from False Summit to summit about 600 m. Viewed from north, thermal area A, near The Boot, is covered by snow, but its location corresponds to shallow dimple in snow surface. Photo by D. Frank. Skamania County, Washington. March 24, 1980. Portion of Figure 149-A, U.S. Geological Survey Professional paper 1250.

Three days before, all had been serene snowfields. Cascades volcanoes tend to look like ice cream cones, with their steep rounded shapes and their deep white coats. Mount St. Helens, for all the seismic excitement, was still a perfect example of the type.

Nothing would ever be the same again.

Oblique aerial photograph of summit of Mount St. Helens, looking south. Location of thermal area A indicated. Note that the new fractures cross ice and rock areas with no apparent change of style, indicating the fractures are deep seated. Photo by D. Frank. Skamania County, Washington. March 27, 1980. Portion of Figure 150, U.S. Geological Survey Professional paper 1250.

Compare the two photos above. They’re the same area. They hardly look it.

The afternoon that had started with a bang continued on a sustained dramatic note. At 2:00pm, seismologists at the University of Washington watched their equipment register a hefty magnitude 4.7 earthquake, the second-strongest of the swarm. They couldn’t see events on the mountain, but others witnessed a gigantic black plume unfurling to a respectable 2,134 meters (7,000 feet). Earthquakes during the eruption happened at such a frequency that seismologists had trouble telling them apart on the graphs. David Gibney, an aerial spotter for the United States Forest Service, saw fractures open and close, the north flank break and rise, as he flew over in the hours after that first eruption. Think of that: a mountain, hurling ash and steam, cracking and breaking beneath your gaze. Something dramatic, indeed.

At the end of that opening sequence, Mount St. Helens sported a crater 61-76 meters (200-250 feet) across nestled within the old, ice-choked summit crater. The summit had been cracked like an egg, split open by an eastward-trending fracture that slashed her flanks from northwest to northeast, a gash measuring nearly 1524 meters (5,000 feet) in length. Other fractures ran alongside it. They defined the south side of an uplifted block, possibly already pushing outward, on her north flank.

The Bulge had been born.

View from the NW, March 30, 1980, showing the summit graben, the north-side bulge, and an on-going steam eruption. Note the dark gray pulverized rock falling on the south side of the mountain. Annotations: north and west sides of the mountain are marked; a curved arrow shows the continuing movement of the the north side bulge; dotted lines show the approximate edges of the summit graben; double-headed arrow illustrates extension across the graben. Image courtesy USGS, annotations and caption by Lockwood DeWitt.

Previous: Prelude to a Catastrophe: “The Unusual Character of the Seismic Activity Became Clear.”

Next: Prelude to a Catastrophe: “Pale-blue Flames.”

References:

Klimasauskas, E. and Topinka, L. (2000-2010): Mount St. Helens, Washington, Precursors to the May 18, 1980 Eruption. Cascades Volcano Observatory website, USGS (last accessed June 13th, 2012).

Korsec, M.A., Rigby, J.G., and Stoffel, K.L. (1980): The 1980 Eruption of Mount St. Helens, Washington. Department of Natural Resources Information Circular 71. (PDF)

Lipman, Peter W., and Mullineaux, Donal R., Editors (1981): The 1980 Eruptions of Mount St. Helens, Washington. U.S. Geological Survey Professional Paper 1250.

 

Originally published at Scientific American/Rosetta Stones.

What’s New at Rosetta Stones, Plus You Could Be a Rock Star in the Kitchen!

For those of you who rely on ETEV to keep you up to speed on happenings at RS, here’s a little list.

We’ve had a sing-song. If any of you are inspired to share your own favorite geologically-themed songs, you may do so at any time. I plan to keep the Tuesday Tune thing going for a while.

Figured it was time to republish The Seduction of Subduction, complete with many fresh new photos.

And for the Mount St. Helens aficionados, here’s how it changed everything.

As a special bonus for ETEV readers only, this is a super-awesome video I found whilst perusing geology songs on YouTube.

I may have to set up a geology kitchen, because that looks delicious.

Prelude to a Catastrophe: “The Unusual Character of the Seismic Activity Became Clear”

This is the trouble with beginnings: the beginning is often subtle, and unrecognizable at the time. It’s only in retrospect that we can go back, look at sequences of events until we find a place to stab a finger down and say, “Here. Here is where it began. This is the time, the place, the event.” Even then, it’s usually only a beginning. There are many places to put the finger, many events to choose.

It began with earthquakes.

Mount St. Helens from Spirit Lake. Skamania County, Washington. August, 1975. Image courtesy Donal Mullineaux, USGS.

Mount St. Helens had always been more seismically noisy than her siblings. Studies in the early 1970s found two types of earthquake: typically “volcanic” quakes high on the mountain, and classically tectonic quakes a few kilometers beneath to the northeast and southwest. Further studies revealed the earthquakes with “volcanic” signatures to be glaciers grating down the mountain. None of this was unusual for an ice-covered volcano in a tectonically feisty area.

The moving finger moves on through the 1970s, reaches March of 1980, hovers and stops. Here. March 16th.

It was just a small uptick in earthquake counts around the volcano. No one pointed to it that day, when the count went up to 13; or on the 17th, 18th or 19th, when the counts had reached 34 per day. Although that daily total nearly equaled the number of earthquakes located near Mount St. Helens for the entire previous five years, it was too early to cry eruption. Loggers were busy building roads: the recorded seismicity could merely be a result of their blasts. No cause for concern. No beginning, until in the midst of the action, prior records are scrutinized in light of certain knowledge, and the moving finger can point with confidence. Here.

There is another beginning.

Seismogram of moderate earthquake recorded on the afternoon of March 20 at station SHW. Image Courtesy USGS.

3:47pm Pacific Standard Time, March 20th, 1980. This earthquake is strong, shallow, unlike any of the others. It shakes the ground around the volcano hard enough for people to notice. In Seattle, Washington, a joint group from the University of Washington and the United States Geological Survey, studying seismicity around the mountain in search of geothermal resources, see their instruments record a magnitude 4.2. They don’t know what’s beginning, but they suspect. By the next day, they’re installing new seismometers on and around the mountain. Mount St. Helens is too dangerous to take chances. They need to know.

US Forest Service officials and the UW/USGS seismic research group geophysicists contact Dan Miller, Donal Mullineaux and Dwight Crandell at the USGS Volcanic Hazards Project to report the increase in earthquake activity and seek advice. The three of them had studied the volcano extensively and published a paper in 1978 that outlined her hazards and predicted she would erupt again, possibly as early as the end of the century. This large earthquake and the ongoing aftershocks could be an indication of eruptions to come. Experts in her behavior would be essential.

Seismogram, station SHW, March 21 to March 23, 1980. Frequent earthquakes are being recorded, and the counts are increasing. Image courtesy USGS.

On March 22nd, another magnitude 4 earthquake rattled the mountain, and by the 23rd, it was apparent that the seismometers weren’t recording an aftershock sequence. Earthquakes averaged 15 per hour, the rate was increasing, and though most of the magnitudes remained low – less than 2% reached magnitude 3 or higher – the sheer vigor of the activity made it clear to geologists that they were in the midst of an earthquake swarm unlike anything ever seen in the Cascade Range. And that swarm could be volcanic in origin.

Officials and scientists reacted fast once they identified the sequence as a swarm. As four earthquakes of magnitude 4 or higher, one reaching 4.7, rocked the mountain on March 24th, Pacific Power and Light workers lowered Swift Reservoir to accommodate possible mudflows predicted by Miller, Mullineaux and Crandell’s 1978 hazards paper. The seismology lab at the University of Washington moved to a 24-hour schedule, while seismologists and USFS officials advised the public that staying away from Mount St. Helens would be very wise indeed. Miller, Mullineaux and Crandell obtained data from the National Weather Service and NOAA’s Air Resource Laboratories that would allow them to plot out areas that could be affected by ash fall in the case of an eruption: these predictions would be updated daily. Hazard maps were generated and distributed, allowing officials to plan operations around the mountain during the next six days.

And a plane took to the skies to inspect the mountain for changes.

Oblique aerial photographs of the Mount St. Helens summit area showing historic thermal areas. Distance from False Summit to summit about 600 m. Viewed from southwest, thermal area B appears as a cluster of snow-free patches of ground. Photo by D. Frank. Skamania County, Washington. March 24, 1980. Portion of Figure 149-B, U.S. Geological Survey Professional paper 1250. Image courtesy USGS.

Nothing. No major changes other than a few avalanches, no deformation or fracturing. The historic thermal areas hadn’t heated up. Everything appeared quite normal, despite the rumblings below. The old girl was definitely up to something, but you’d never know it from her serene exterior.

The moving finger, flitting restlessly between events of increasing interest, stabs down on March 25th with a decisive thump. Here. Here’s where it begins getting dramatic.

Within a single hour, five earthquakes larger than magnitude four rock the volcano, and before the day is done, the total of magnitude 4+ quakes reaches 25. The poor seismic station on the western flank can’t keep up. It’s saturated with quakes by early afternoon. Little ones are drowned out by larger; the graph, usually full of discrete wobbles, is nearly solid black. As the FAA restricts airspace over the mountain, scientists and photographers flying over the summit during peak seismic activity see new fractures cracking glaciers; rockfalls and avalanches cascade down the slopes. Photographer Bud Kimball tells the USGS he’s spotted a considerable crack in the snow at the summit. Things are obviously getting intense.

An Emergency Coordination center is set up in Vancouver, WA, and the USFS, fearing avalanches could reach as far as Spirit Lake, close the information center there. They restrict access to the volcano above the treeline, and close several forest roads to keep the public out of harm’s way. Donal Mullineaux flies to Vancouver as intense earthquake activity continues through the night. Events have progressed so far that one of the three men who are most intimately familiar with St. Helens’s propensity for violence needs to be on-site to assess the situation.

Seismogram from stations SHW and CPW, for March 24 to 25, 1980. Earthquake activity has increased dramatically, saturating the records. Image courtesy USGS.

Mullineaux outlined her potential dangers in a March 26th meeting for government representatives and private industries affected by her antics. He explained the types of eruptions they might expect, and outlined what their result could be. His warnings prompted the USFS and county officials to close off areas of St. Helens beyond her flanks. As they worked to assess hazards and protect the public, earthquakes continued, including seven larger than magnitude 4. Those earthquakes were worryingly shallow: less than 5 kilometers (3 miles) beneath the volcano. Seismologist Stephen Malone and his team looked at the totals: 10 earthquakes of magnitude 2.6 or higher between March 20th and 11:00am PST, 174 between the 25th and the 26th. They would later state in a paper on their work, “We did not see how this activity could continue without something dramatic happening.”

Neither could any other geologist. With that exponential increase in earthquake activity, they take swift action. On the morning of March 27th, the USGS issues a Hazards Watch. The Army National Guard flies a reconnaissance mission over the volcano: at 11:20am PST, they spot a hole with a gray streak in the ice cap near the summit.

At 12:36pm, a loud boom echoes over the ridges and valleys near the volcano.

The moving finger stops. Here. Here is where Mount St. Helens proved all the scientists suspecting an eruption 100% correct.

Here is where her explosive phase begins.

Mount St. Helens’ eruption, first crater, from the north. USGS Photograph taken on March 27, 1980, by David Frank.

Previous: Prelude to a Catastrophe: “One of the Most Active and Most Explosive Volcanoes in the Cascade Range.”

Next: Prelude to a Catastrophe: “Something Dramatic.”

References:

Klimasauskas, E. and Topinka, L. (2000-2010): Mount St. Helens, Washington, Precursors to the May 18, 1980 Eruption. Cascades Volcano Observatory website, USGS (last accessed June 13th, 2012).

Korsec, M.A., Rigby, J.G., and Stoffel, K.L. (1980): The 1980 Eruption of Mount St. Helens, Washington. Department of Natural Resources Information Circular 71. (PDF)

Lipman, Peter W., and Mullineaux, Donal R., Editors (1981): The 1980 Eruptions of Mount St. Helens, Washington. U.S. Geological Survey Professional Paper 1250.

 

Originally published at Scientific American/Rosetta Stones.

Prelude to a Catastrophe: “One of the Most Active and Most Explosive Volcanoes in the Cascade Range”

Imagine being an extraterrestrial geologist in geostationary orbit above the Pacific Northwest in the 1970s. You’re the first explorers to reach Earth (underpants-thieving aliens aside), and you haven’t got a lot of data on this little blue marble. But your own planet has plate tectonics, so you’re familiar with the landforms caused by the process.

You have a look through your sensors, and see a conga line of volcanoes weaving up the continent.

Map of the Cascadia Volcanic Arc by NASA. Image courtesy Wikipedia Commons.

Now, your image wouldn’t be labeled, of course. But you can see a trench offshore, and a zig-zaggy ridge, so you can sketch in some very small oceanic plates busily subducting beneath the continent. The line of coastal mountains and that volcanic arc, less than a hundred miles from the sea, would have given the game away even if you didn’t have super-cool sensors that can see beneath the sea. You know there’s an active subduction zone here.

You run further scans. Some of the volcanoes in that arc are fairly young, and have been active in the recent past. You do a quick north-to-south sweep, and notice Mt. Baker still steaming away. Glacier Peak has a 300 year-old coating of ash. Mount Rainier is riddled with hydrothermal anomalies, cooking itself from the inside: it’s so rotten you can see evidence of mudflows barely over a decade old. Mt. Adams doesn’t seem to have erupted for the past few thousand years, but hydrogen sulfide fumaroles puff away atop it. And, a short jog to the south, Mt. Hood has also got active fumaroles. Any of these volcanoes could erupt at any time. The cities you see, located in the shadows of these restless mountains, had better watch out.

But it’s one volcano in particular that’s caught your eye (or eyestalk): just to the west of Mt. Adams, the most symmetrical of the lot. It’s not the tallest, but it’s the youngest. The others are hundreds of thousands, all the way up to a million, years old. Mount St. Helens is a barely-adolescent 40,000. And it’s been extremely active.

Computer-generated vertical view of Mount St. Helens, from photos taken August 5, 1972. Data were filtered by averaging pixel values over areas.  Image courtesy USGS.

You zoom in for a closer look. You see evidence of lahars, pyroclastic flows, ash falls, and lava flows. And you notice a dedicated geologist, scrambling over the outcrops. You don a disguise and beam down to chat him up. His name is Dwight “Rocky” Crandell, and he’s been doing an exhaustive study on Mount St. Helens’s eruptive history. It’s almost complete. And he’s concerned: this young volcano has been quite the firecracker. It’s likely to erupt before the end of this century, he tells you. Being close to population centers, it could cause quite a mess. So it’s important to understand its past behavior in order to assess the risks it poses.

You sit with him for hours, and learn more than you could have possibly hoped. By the end of your discussion, you know this volcano’s history intimately. And you’re intrigued. You can’t help but to be. Dr. Crandell has an infectious passion for geology, and Mount St. Helens is just the kind of volcano that repays that interest in spades.

Mount St. Helens’ sunset before 1980. The peak’s symmetric cone earned it the title of the “Fuji of North America.” USFS photo courtesy of Jim Hughes.

You learn there are two parts to this seemingly single mountain. Dr. Crandell divides it into Old Mount St. Helens, which was built mostly of volcanic domes and short, thick lava flows between 40,000 and 2,500 years ago, and the modern cone that was active as little as a century and a quarter before. He and other geologists, working diligently for many years, have divided her eruptive history into a number of stages and periods. When he’s finished describing them, you have one good English word to describe her: explosive.

You give a précis of what you’ve learned to your team of intrepid explorers when you return to your ship.

First, you tell them, your suspicions of a subduction zone have been confirmed. Earth scientists only recently discovered plate tectonics, but they’ve done an excellent job figuring it out. Just off the coast near Mount St. Helens, a small plate they’ve named the Juan de Fuca is subducting beneath the North American continent. And this has given birth to a very lively chain of volcanoes called the Cascades.

Mount St. Helens was born during the Ape Canyon Eruptive Stage, beginning before 40,000 years ago, and going on until about thirty-six thousand. It was an explosive birth: Dr. Crandell found plenty of pyroclastic flow deposits and a lahar. Ash clouds left blankets of tephra so thick that even tens of thousands of years later, the layers can be recognized – they’re called tephra set C. Both lithic (pulverized stone) and pumiceous (made of pumice) ash blasted out of the baby volcano. One or more lava domes and flows emerged.

After a noisy introduction to the world, Mount St. Helens fell silent. Then the Cougar Eruptive Stage began about 20,000 years ago, and lasted for around two thousand years. During this episode, she produced plenty of dacite eruptions. Pumiceous pyroclastic flows, the eruption of tephra sets K and M, lahars, and debris avalanches kept things hot. She filled the Lewis River Valley over a hundred meters (over 328 feet) deep – the deposits might have piled up to 115 meters (337 feet). A high-silica andesite lava flow joined the excitement. By the time she was done, she’d grown to 1,825 meters (5987.5 feet). Not bad for a youngster!

She slept for around 5,000 years. The Swift Creek Eruptive Stage, beginning around 13,000 years ago, produced more explosive eruptions. Tephra sets S and J blasted out of the mountain during this time. Lithic and pumiceous pyroclastic flows roared down her slopes and into her valleys. Lahars buried streams in mud and rock. Dacite domes pushed their slow, thick way to the surface. By the end, about 10,000 years ago, fans of rocky debris flanked those domes.

Five and a half thousand years of quiet followed. Then she began her Spirit Lake Eruptive Stage, which is still ongoing. Deposits are abundant enough to begin dividing her antics into periods. And during this time, things changed.

The Spirit Lake Eruptive Stage began with the Smith Creek Eruptive Period, which followed the familiar pattern: energetic eruptions spreading tephra all over the place (tephra set Y in this case). Pyroclastic flows. Lahars. Domes. The only thing really different about this time was the amount of pumiceous tephra she erupted: only the Ape Canyon Eruptive Stage could match it.

Mount St. Helens napped for a brief three hundred years, then woke up 3,600 years ago for her Pine Creek Eruptive Period. This explosive episode produced several pyroclastic flows, tephra set P, and several domes. Dr. Crandell found a remnant of a dome of that age at 2,200 meters (7,218 feet), so she’d attained quite a respectable height. She was still basically a mound of domes and piles of debris. Folks back then might not have been calling her symmetrical.

She took another three hundred year nap before the Castle Creek Eruptive Period, which began 2,200 years ago and marked a change in her style. She mixed it up, starting with dacite eruptions (her old favorite), followed by some andesitic activity that produced ash clouds and a lava flow. After that andesitic interval, she returned to her tried-and-truce dacite style, producing her patented air-fall tephra, pyroclastic flows, and likely a dome. She switched back to andesite for a bit, then really mixed it up with some respectable basalt flows. By the end, she had produced tephra set B, and boasted some very nice lava tubes within her basalts. She’d become a true stratovolcano, attained nearly her full height, and begun to assume her classic symmetrical shape.

Ape Cave, Mount St. Helens. This is a lava tube formed in basalt flows of Castle Creek age. Image credit Dan..

Silence fell for about six hundred years. Then, around 850 AD, she began her Sugar Bowl Eruptive Period and emitted her first lateral blast while building Sugar Bowl Dome. Dacite blocks up to 30 centimeters (nearly 12 inches) in diameter were hurled as far as 4.5 kilometers (2.8 miles). Pyroclastic flows and lahars roared down her flanks. She deposited tephra set D, along with a warning: sometimes, she didn’t blow straight up. This brief episode ended within fifty years, but she didn’t stay quiet for long.

In 1480, the Kalama Eruptive Period began with explosive eruptions. In 100 years, she deposited tephra sets W and X, built domes, and released andesitic lava flows that all combined to build her to her pre-1980 shape. All she needed was a few finishing touches.

She put those on during the Goat Rocks Eruptive Period, which lasted from 1800 to 1857. Explosive eruptions of pumice, an andesite lava flow, and the emergence of Goat Rocks Dome, accompanied by hot avalanches and lahars, completed her picture-perfect shape. She also gave a traveling artist something to paint home about.

Aerial view from southeast of lower part of "Floating Island" lava flow from Mount St. Helens. Skamania County, Washington. September 28, 1979. This flow was part of the Goat Rocks period. Image credit USGS.

And that was it, as far as hard-working geologists could determine: a history as complete as erosion and repeated explosive activity would allow. Before you left him, Dr. Crandell had impressed upon you the certainty that Mount St. Helens would erupt again. And you knew from 40,000 years of her habits that she liked going off with a bang. So, while you continued your surveys of Earth, you periodically returned to her, just to check. Other volcanoes erupted around the world, but Mount St. Helens slept on. You began to believe she might not erupt before your survey mission was done.

And then, in mid-March, earthquake counts began to rise. At first, it didn’t seem like much, just a spike in the background tectonic activity one expects in a subduction zone studded with restless volcanoes. But then came March 20th. At 3:47 pm Pacific Standard Time, the earth rumbled and shook with the force of a magnitude 4.1 earthquake. It was just a smidge to the northwest of the summit. It was very, very shallow. And it wasn’t like anything seismologists (or we imaginary extraterrestrials) had ever seen round her before.

Seismogram of moderate earthquake recorded on the afternoon of March 20, 1980, at station SHW.  Image credit USGS

Geologists and seismologists looked at that earthquake trace, and knew: this could be it.

Previous: Prelude to a Catastrophe: “The Current Quiet Interval Will Not Last…”

Next: Prelude to a Catastrophe: “The Unusual Character of the Seismic Activity Became Clear.”

References:

Crandell, Dwight R. (1987): Deposits of Pre-1980 Pyroclastic Flows and Lahars from Mount St. Helens Volcano, Washington. USGS Professional Paper 1444.

 

Originally published at Scientific American/Rosetta Stones.

The Field Trip Continues at Last! Fun Times at Coldwater Lake

I know, I know, I’ve been an absolute space cadet these last few weeks. Rather odd combo of sewing projects, Apple product releases, and a touch o’ depression, y’see. My brain’s been a bit on the quiet side. It’s really hard to jolt the bugger into useful work when all it wants to do is figure out the next phase of extreme bag mayhem. I apologize for the lack of adequate content around here, and also in advance for all of the eyeballs I’m going to damage the next time I see you in person. I’ll post pictures when the bag is done so that you may be forewarned. Bring sunglasses.

Anyway. Never mind all that. There’s finally a new stop in our Mount St. Helens field trip! We’ve made it to Coldwater Lake, and it’s lovely. Go enjoy a very young body of water, born on May 18th, 1980.

Look, I’ll even give you a preview of it from Coldwater Ridge:

Mount St. Helens and Coldwater Lake from the Coldwater Ridge Visitor's Center. There's a mighty fine delta, if you know where to look. Hooray for hydrogeology!

Mount St. Helens and Coldwater Lake from the Coldwater Ridge Visitor’s Center. There’s a mighty fine delta, if you know where to look. Hooray for hydrogeology!

How yummy is that?

At Last, The Perfect Snark for the “Criticism Murderer Mah Freeze Peaches !” Contingent

You patrons of our fine Freethought Blogs establishments have undoubtedly run into the ridiculous folk who whine and howl about how we killed their free speech with nasty criticism. There’s one such meltdown just this week, which promised to be at least mildly entertaining – until The Denver Atheist took his ball and sulked home, thus infringing upon my right to pursue happiness at his expense.

Still. Must admire his ability to stick a flounce for over twelve hours, a skill which is vanishingly rare amongst those who cry about how meeeaaaannnn we are and say they’re really really leaving and they totally mean it this time. No, seriously, they’re outta here. This time – no, this time – well, definitely this time, they are so leaving because we are soooooo mean and awful that they’ll never be back again. Except for all those times they come back to tell us how mean we are and how right they are before leaving again for reals this time…

Our Freeze Peach Warrierz are nothing if not obsessively devoted to their causes, especially the cause of giving the rest of us headaches from chronic eye-rolling.

And really, what do you say to people stupid enough to argue that we are Taking Away All the Freeze Peaches by exercising our own?

The fine folks at Wonkette, who have some Freeze Peach Crusaderz of their own, have decided to turn a mirror shined with premium snark upon the doughty brigades:

But aren’t we free to write say what we want in this country? We are writing what we think is best for our blog and are not forcing our beliefs on anyone else. Why would you write a comment that disagrees, “sanwin?” Haven’t you ever hear of something called “freedom of speech”? Stop oppressing us with your words, which make it impossible for us to do freedom! This is Amercia!

I shall engrave this paragraph upon something gleaming and durable, with a blank space for the name, and present it to each intrepid Freeze Peach Warriur who comes round crying about how Criticism Equals Tyrrany. Because, really, such behavior thaws mah peaches right out. Sheesh.

Great Moments in Horseback Archery: Shoulda Had a Bigger Shield

One thing you should never do, if you’re the leader of a company of equestrian experts, is allow the Viking announcing events direct the audience to choose your shield. Given a choice between large, medium, and comically microscopic, you can imagine what everybody chose.

The Viking's assistant holds up a shield for the audience's inspection, as Alan looks on.

The Viking’s assistant holds up a shield for the audience’s inspection, as Alan looks on.

No, not that one.

Alan graciously accepts the infinitesimal shield the audience has chosen by popular acclaim. We're such evil barstards...

Alan graciously accepts the infinitesimal shield the audience has chosen by popular acclaim. We’re such evil barstards…

Yepper. That’s the one. You’ll have to look closely – it’s that wee silver thing that looks like a mini flying saucer.

Alan was very gracious about it.

Now, firing arrows from horseback is rather difficult. You’re steering something that’s got a mind of its own with your knees. You’re trying to draw your bow with a rather large head and neck in the way, and believe me when I say that even a canter is quite bouncy and prone to throwing off your aim. No surprise that Laurie missed her first shot.

However. She only missed once…

She draws.

Laurie aims at Alan.

Laurie aims at Alan.

She shoots! She scores!

You can see the arrow has left the bow. Note that Alan is holding the shield in a wise place - wise until you realize the thing's designed like a bulls-eye...

You can see the arrow has left the bow. Note that Alan is holding the shield in a wise place – wise until you realize the thing’s designed like a bulls-eye…

Oh, my, did she ever not miss this time round.

An enlarged version of the above, showing where Alan has bravely taken the shot.

An enlarged version of the above, showing where Alan has bravely taken the shot.

If you’re having trouble seeing the arrow, click through for a larger version and pay especial attention to where the shield is.

Well, needless to say, Alan demonstrated that even in full plate armor with a small but thick shield, taking an arrow to the crown jewels isn’t the best experience.

Alan crumples as Laurie rides to victory.

Alan crumples as Laurie rides to victory.

Mind you, I think he was playing it up for dramatic purposes. These were, after all, blunt arrows. And he did have quite a lot of steel on.

Laurie wasn’t done with him yet, though. In the video that follows, the maniacal laughter is courtesy our Viking announcer. It’s not quite right, is it?

However, you can see Alan recover quickly, and in a future video, you’ll see him hamming it up thoroughly, and so a good time was had by all.

And once again, my little point-and-shoot got the shot.  Thing’s almost as awesome as the Free Lancers.

Great Moments in Jousting

Sharpen your eyes and don’t look away: you’re about to see a very unusual moment in jousting.

Did you see the tips crack against each other and come flying apart? That was bloody amazing is what that was. Amazing enough I spent all night fighting with various video editing programs to put together something that would at least attempt to do it justice. Just imagine being there…

Anyway. Thee shall have some lovely photos of the two heavy horses – these animals weren’t bred for slim lines and elegance, they were selected for strength and endurance. It takes a lot of power to haul around knights in full plate armor.

The lighter heavy horse strutting its stuff in the lists.

The lighter heavy horse strutting its stuff in the lists.

Still beautiful, aren’t they?

The Palamino Jouster poses prettily.

The Palamino Jouster poses prettily.

Check out the hooves on these animals – they can cause the ground to tremble as if there’s an earthquake in the offing.

Nice conformance, that horse. Don't let it step on you under any circumstances.

Nice conformance, that horse. Don’t let it step on you under any circumstances.

I want one of each, please.

Anyway. Yes. I’ll be working on the trebuchet montage soon, probably over the weekend – it’s a lot of stuff to work with. In the meantime, I promise I’ll have the occasional new bit of substantive commentary, plus many more horsies. Wait until you see what happened during the archery exhibition. Poor dude shoulda had a bigger shield…

Broughtcha Horsies

I told you I would, didn’t I? Oh, I’ll have far, far more, but this should whet your appetites.

I love the fact they had miniature horse carriages this year. Awesome! Many, many women demonstrating mad skillz in medieval equine martial arts – yet moar awesome. And I discovered that standing beside one of the speakers means I don’t have to fiddle with audio. That’s conveniently provided. Heh.

Alas, there will be no portraits of moi with horsies – we had to rush back home to watch over Luna, who just got out of surgery. Not that you’d know it from the way she was all over the house playing with absolutely everything, at least until the vaccines kicked in and made her drowsy. I hope my hysterectomy goes as well when I finally manage to convince someone to give me one.

Everyone give a big round of applause, including shouts, whistles, and various assorted noisemakers, to our own Trebuchet, who owned the competition once again. There’s a reason we call him Trebuchet, people.

Pumpkin hurling on the way. There’s an air cannon, even. I just have to cut together a nice montage out of all the raw footage, and you shall have pumpkins being chunked. Plus many horsies.

The Faire continues today for those who are in the area and want to go have a great time.