Kiss Your Ash Goodbye: The Yellowstone Supervolcano, Part I, A Vulcanology Primer By Stephanie Osborn

Kiss Your Ash Goodbye: The Yellowstone Supervolcano, Part I, A Vulcanology Primer

By Stephanie Osborn

Excerpted from Kiss Your Ash Goodbye: The Yellowstone Supervolcano, © 2018

Images in this article are public domain unless otherwise noted.

What is a supervolcano?

“The term ‘supervolcano’ implies a volcanic center that has had an eruption of magnitude 8 on the Volcanic Explosivity Index (VEI), meaning the measured deposits for that eruption is greater than 1,000 cubic kilometers (240 cubic miles).” ~U.S. Geological Survey

That said, often volcanic eruptions with a slightly lesser VEI of 7 are also considered supervolcanic. This is because the VEI does not take density of ejecta into account. Magma chemical composition varies, depending upon the source of the melt. This can produce lava with varying densities.

Crater Lake, in Mount Mazama, with Wizard Island cinder cone.

What is the Volcanic Explosivity Index?

It is a means of ranking a volcanic eruption, similar to the Richter or moment magnitude scales for earthquakes. According to the U.S. Geological Survey, “The Volcanic Explosivity Index (VEI) is a relative measure of the explosiveness of volcanic eruptions. It was devised by Chris Newhall of the United States Geological Survey and Stephen Self at the University of Hawaii in 1982.” It categorizes eruption characteristics, such as volume of ejecta, eruption cloud height, etc. Again quoting the USGS, “The scale is open-ended with the largest volcanic eruptions in history (super-eruptions) given magnitude 8.” Since it is open-ended, some geologists do estimate that a very small number of eruptions in geologic history may have reached a 9, though such a rating is currently unofficial.


VEI Ejecta vol


Type Description ~Freq. Plume Troposphere Stratosphere
0 <104 m3 Hawaiian Effusive continuous <10m negligible none
1 >104 m3 Strombolian/


Gentle daily 100m-1km minor none
2 >106 m3 Vulcanian/ Sub-Plinian Explosive every 2 weeks 1-5km moderate none
3 >107 m3 Peléan/ Sub-Plinian Catastrophic 3mo. 3-15km substantial possible
4 >0.1km3 Peléan/ Sub-Plinian Cataclysmic 18mo. >10km substantial definite
5 > 1km3 Peléan/ Plinian Paroxysmic 12yrs. >10km substantial significant
6 >10km3 Ultra-Plinian Colossal 50-100yrs. >20km substantial substantial
7 >100km3 Ultra-Plinian Super-Colossal 500-1000yrs. >20km substantial substantial
8 >1000km3 Ultra-Plinian Mega-Colossal >50,000yrs. >20km vast vast

The Volcanic Explosivity Index.

Are all supervolcanoes explosive?


There are supervolcanoes known as “traps” which tend to be nonexplosive. These are typically long cracks — sometimes fields of parallel cracks — from which vast quantities of lava (“flood basalts”) flow over the surrounding terrain. The term refers to the step-like terrain common to such features. One of the best known in the geological community were the Deccan Traps. This eruption occurred some 60 million years ago in the Deccan Plateau region of what is now India. The residual lava beds originally may have covered some 580,000sq.mi. (1.5million km²) — more than 2x the size of Texas. Multiple flows over time covered the area in ~6,600ft (2,000m) thick basalts. It is one of the largest volcanic features on Earth.

How strong is a supervolcano?

That depends on the type of supervolcano and your definition of “strong.” There are two types of supervolcano:

1) Megacalderas, or “massive eruptions”:

These are cliff-edged craters, usually (though not always) NOT surrounded by a mountain, where the violence of the eruption emptied the magma chamber. The overburden collapsed into the chamber, leaving a sinkhole-like depression.


Lake Toba — the lake IS the caldera.

2) Traps, or Large Igneous Provinces:

As already mentioned, these are huge regions of lava flow resulting from flood basalt eruptions, often hundreds or thousands of square miles with volumes on order of millions of cubic miles. The lavas are normally laid down in sequential eruptions over millions of years.


Siberian Traps lava flow. Image credit Benjamin Black via USGS.

While traps are considered supervolcanoes, usually it is the megacaldera which is being referenced, due to its violence.

What is the difference between traps and megacalderas?

Traps tend to be effusive and megacalderas tend to be eruptive. This is not always true but usually is. The difference lies in the chemistry of the melt.

Effusive flows tend to have thin, runny lava (low viscosity), usually basaltic in composition. Dissolved gases escape quickly. This produces dramatic lava fountains and swift flows. Example: Kilauea.

Eruptive flows tend to have thick, viscous lava (high viscosity), usually granitic in composition. Dissolved gases are held in the melt.  Pressure builds, and an eruption ensues when the containment (volcanic vent/neck/chamber) fails. Example: Mt. St. Helens.

If the melt chemistry changes for any reason, a trap can become eruptive, or a megacaldera can become effusive, at least temporarily.

How strong is a supervolcano? (Take two)

When Mt. St. Helens erupted, it released thermal energy equivalent to approximately 24 megatons (MT). 7 MT of this was expended in the blast alone. The St. Helens eruption was a VEI 5.

As previously mentioned, the Volcano Explosivity Index is logarithmic. A supervolcano eruption is VEI 7-8. This is 2-3 orders of magnitude stronger than St. Helens. A supervolcano, therefore, would release an estimated 2,400-24,000 MT (2.4-24 gigatons (GT)) of thermal energy. If we scale the blast size up proportionally, this would result in a blast equivalent to approximately 700 MT to 7 GT.

How many supervolcanoes exist?

That depends on who you talk to, and what criteria they are using. Some say as few as half a dozen, others as many as 20 or more.

Keep in mind, there may also be ocean-floor volcanos of which we’re unaware.

A Partial List of Known Active/Dormant Supervolcanoes Currently In Existence

  • Aira Caldera/Sakurajima, Kagoshima, Japan
  • Baekdu Mountain, China/North Korea border
  • Campi Flegri/Phlegraean Fields, Naples, Italy
  • Cerro Galan Caldera, Catamarca province, Argentina
  • Kurile Lake/Kurilskoye Lake, Kamchatka, Russia
  • La Pacana, Zapaleri tripoint, Chile/Bolivia/Argentina
  • Lake Toba, North Sumatra, Indonesia
  • Long Valley Caldera, Mammoth Mountain, California, USA (south of Mono Lake)
  • Macauley Island, New Zealand
  • Mount Aso, Kumamoto Prefecture, Japan
  • Tambora, Sumbawa, Indonesia
  • Taupo Caldera, North Island, New Zealand
  • Thera/Santorini, Santorini, Greece
  • Valles Caldera, Santa Fe, New Mexico, USA
  • Yellowstone Caldera, Yellowstone National Park, Wyoming, USA


To obtain a copy of Kiss Your Ash Goodbye: The Yellowstone Supervolcano by Stephanie Osborn, go to: Kiss Your Ash Goodbye.


153 thoughts on “Kiss Your Ash Goodbye: The Yellowstone Supervolcano, Part I, A Vulcanology Primer By Stephanie Osborn

  1. I highly recommend a trip to Lassen National Volcanic Monument for anyone who is lightly interested in vulcanology. The visitor center has a lot of good basic information, and all four of the main types of volcano (shield, cinder cone, lava domes, and composite/stratovolcanos) are present in the park.

    Plus it is very pretty, fairly easily accessible, and you can hit the major features in one day and head off to a city to stay in a hotel if you desire. (That city would be Redding, so… maybe not right this moment.)

    1. Red Bluff is also possible, and closer to Bumpass Hell, the most accessible field of mudpots and such in the park. Take SR 36 from Red Bluff to get there.

      1. I like a loop, from south (Red Bluff) to north (west) end (Redding.) When we went a few years back, it was visitor’s center, the sulfur springs, Bumpass Hell (with a 6-year-old, a 4-year-old, and me carrying the baby in a front pack WHILE wearing a skirt), then driving to an interpretive trail, then taking photographs on the way out. I’d like to go camping there; I’ve heard Manzanita Lake is quite nice.

        1. I liked the loop when I was living in Silly Valley. The eastern section of the park has some easy backpacking, though (last time I was there) it was a longish way from SR 44 to Butte Lake campground on a so-so gravel road. Once there, you could hike to Snag Lake. Clockwise got you through a forest, while widdershins set you alongside a cinder cone near the trail head. South of Snag is Juniper lake, and I gather there’s another way into the park from the SE.

          Not sure if any of these have avoided the fires; Susanville got a nasty one, and Cali’s been on a roll with respect to screwing up parkland this year. [sigh].

  2. Bought the book this weekend, and I’ve already finished it and left a 5 star review. This is the kind of science writing we need for the schools.

    1. Alas, milady Steph partakes in forbidden thought just by associating with the white Mormon male, Sarah A. Hoyt, so chances are, the screeching harpies would drown it out.

      1. A Boy Named Sarah? Is that the sequel to Johnny Cash’s, “A Boy Named Sue?” Why am I the last one to find these things out? Skepticism, or am I just an ignorant hick?

            1. Well, they are considered among the highest authorities in modern SF . . .

          1. I thought the proper descriptive was “great”? (My scale is “nice,” “great,” “fantastic-but-those-must-hurt,” and “mouth-open-in-amazement-followed-by-close-your-mouth-fool-they-cannot-be-real”.)

            Um. Interesting thing I just found out about Firefox. “fantastic-but-those-must-hurt” is in the default spellcheck dictionary. Code geeks, what can I say?

            1. That specific phrase isn’t in the spellcheck dictionary, it just breaks up any hyphenated series of words at the hyphens and looks up each word in the dictionary. E.g., try typing this-is-a-mispelled-example and you’ll see a red squiggly under the misspelled word “mispelled”, but not the other words in that hyphenated phrase.

              1. Hmm. I obviously can’t reproduce the squiggly here, but all of “mouth-open-in-amazement-followed-by-close-your-mouth-fool-they-cannot-be-real” has one. The other does not.

                Just to be sure, copy-paste and edit, being in a caffeine-deprived state: mouth open in amazement followed by close your mouth fool they cannot be real. Nope, not a single squiggle.

                I stick to the original hypothesis here, speaking as one who still has a few issues of his early computer magazines laying around.

              1. Back in the winter I ended up on a 10-day round of amoxicillin. Started improving; halfway through, I plateau’ed and started getting worse. Doc had to add a z-pack ON TOP OF the amox, and it was several months before I had anything like enough breath to talk for more than about a sentence without panting.

                I’ve had crud and rattling in my chest ever since, to varying degrees, so I’m not sure it all cleared out properly. If it goes to getting worse, I will probably have to take more antibiotics.

      1. FWIW, I was informed last fall by a radio host who interviewed me that his HS/college instructor friend intended to use my New Madrid fault system ebook as a textbook in his classes on same. I was pleased.

          1. Well, he said, anyway. Whether they followed through, I couldn’t say. The guy may have just been schmoozing. I haven’t seen signs of large sales at the beginnings of quarters or anything.

  3. I’ve always known Yellowstone was a super volcano. Been there a lot. It is difficult to visualize as it is so big, & even on a clear crisp day it is difficult to see the ring of “mountains” (edge of the caldera) from the last eruption.

    Did not know there were 2 more in the US. Wow. Plus we have Crater Lake, although it is suppose to be 100% done.

    That much force is … well wow.

    I witnessed, from the backside, the main & subsequent eruptions of Mount St. Helens. We were in Longview, WA. The drive Columbia Heights Road takes you high enough that we had a direct line of sight to the backside of the main eruption, including all the lightening spawned, from about 30 or 40 miles away. If forest hadn’t been in the way, we’d been able to see the mud flow threaten the I-5 bridge from there, but no.

    Even then the magnitude of destruction was (personally) under estimated until I saw it years later when they opened the National Park.

    1. The recognition of Yellowstone as a supervolcano is actually relatively recent, and occurred during my lifetime. The research took place in the 60s-70s, and was confirmed by space-based imagery. If you think about it, it makes sense why it wasn’t recognized before; it’s so blasted BIG, and instead of a mountain, you have a depression.

      1. In the late ’60x, I went with my folks to the Southwest. We were from the Chicago(spit)–totally a word in 21st century–and didn’t know a butte from a cinder cone. When we were at Bandelier, beyond a trip to the Los Alamos museum, Dad took us for a drive to see the Jemez Mountains volcano. Couldn’t find it, though my 15 year old self had a sense of something odd. “Folks, that great big round valley we drove through? That was the caldera.”

        I’m in lava-blob spitting distance from what’s left of Mount Mazama. We have a very good selection of obsidian and pumice, and I have a great respect for volcanos. Pele and Vulcan, I’d appreciate it if you took a break for a millennia or two.

      2. Yes. Recognized when I was a child, mid-teens.

        Just means that good ole continental USA has 3 natural ways to really mess up our neighbors & the world. Not to mention what it would do to us, but of coarse it would be our fault …

        1. In my case, that would have been about the time they were figuring it out.

          And no, we have more than 3. That’s only the number of currently-capable-of-erupting, VEI 8s that we have. There are other supervolcanos in the CONUS.

    2. When I was in 5th grade my teacher had one of her friends come talk to us about Mt. St. Helens. He had been climbing one of the nearby mountains (can’t remember which one) when St. Helens erupted. He brought a bunch of the photos he had taken with him, several of which had been published in Time (it was one of the big national magazines anyway, but I think it was Time). First hand account of being that close to that eruption was very interesting. Even in ND we got about half an inch of ash on the ground.

      1. He should be glad he was on the other side, then. (I assume he was on the south side, since the thing blew out to the north, more or less.) Still and all, I bet the hike out was unpleasant. It didn’t take many minutes for the ash to start falling over the entire area.

      2. For as close as we were we didn’t see any air blown ash until the following August, when the wind blew our way. We didn’t feel or hear a thing. My folk heard the blast sitting in their boat off of the coast down in Winchester Bay.

        We missed the ash falling on Mt Rainier (where everyone on the mountain had to be “rescued”), where we’d been the day before, intending to tarp camp. BUT, I forgotten the leash for my German Shepard. She was off leash trained so we were fine when we were up & likely would have been okay at night. Was not willing to take the risk with my baby, so we headed home rather than set up camp Saturday night. Got home, didn’t unpack at oh-god-thirty-AM. Next morning the dog got us up to go out, so I was getting breakfast started, while hubby went out to unpack. He came running back in “Turn. Everything. Off. Something. Has. Happened. With. The. Mountain!!!!” Bit of understatement.

        We don’t have pictures of the actual event, but boy do we have piles of slides of the ash & storms from the backside.

        1. Which means he saw it as it was happening, or shortly thereafter. It was Sunday, May 18, 1980, and the quake that caused the slope failure was just past 8:30am local time.

          1. Were those the picture series of the slide going?

            We didn’t see anything until about 9AM (we didn’t get home until 3 AM).

            We saw ash, just didn’t get any on the ground until August 1980.

            Side note. Did see logs as they were pulled out of the woods. Probably the last single to triple log loads anyone will ever see again. Cooked 12 or more inches into the outside cylinder. Everyone pulled out their wood tree id books because we were digging into the uncooked sections to get what we needed for species id. Everything looked the same.

            1. We were living in Longview, Mint Valley section of town. The section behind the dikes. We actually packed up the animals & what we could & left town until we were called back to work. If that new Spirit Lake Dam had gone … may not have seen any ash when she blew, but mud flows ran all the way to the Columbia between Longview & Kelso, even the flows weren’t or barely over ran the river banks by then.

              FYI. When we bought, we bought above the flood plain, by a lot.

              1. I remember the eruption myself, though I’m in the Southeast. I followed the events pretty closely. And when I visited, my friends took me across the Columbia and up the highway that runs along the Toutle River. You could see the remnants of debris flows in places along the river, and there were huge cuts of ash deposit along the river’s banks. And all of the bridges — ALL of the bridges — across the river had structure and architecture less than 20 years old, at the time of my visit…which was like the day before the 20th anniversary of the eruption. (We made sure NOT to come ON the anniversary, and thus escaped the crowds.)

                1. So yeah, I know about the lahar down the river, and how they had to keep dredging the Columbia to keep the shipping channel open, and all that.
                  *shakes head*

                  And that was a scant VEI 5.

                  1. We worked for a 3rd party not-for-profit log scaling outfit. Got called Monday for layoffs (got paid for 2 weeks) were off about a month. There were 20 contracts at the Weyerhauser sort/ship yard. Given what happened to the sort yard up the Toutle & the condition of the Columbia, logs weren’t moving.

                    We decamped to Eugene & Bend for about 10 days (where our folks were).

                2. I remember driving across the plains the next spring and seeing ash from Mt St Helens starting almost as soon as I crossed the Mississippi.

            2. Yes, the quake triggered slope failure and the whole thing went, around 8:32am and some seconds, if memory serves. When the slope slid away, it effectively sabered the cork from the champagne bottle, as it were, and the pressure blew out the side as a result.

              So you saw it probably less than half an hour after it blew.

              I talked with several of the park rangers when I went to the observatory on Johnston Ridge, just about the 20th anniversary of the blast, and all indications are that the blast/pyroclastic flow hit Mach, coming across the intervening valley. They said there was a scant 10-15 seconds of carrier signal on David Johnston’s broadcast (“Vancouver! Vancouver! This is it! This is it!”) after he stopped talking, before even the carrier signal fell dead.

              They never found his body, or any remains at all, really. The entire face of the ridge (which had no name until then, but was named after him) was scoured clean of all vegetation, all soil, and even some of the bedrock. There were a couple of twisted, charred stumps that I recall, near the top of the ridge, and the backside of the ridge was littered with little bitty splinters of wood.

              They showed a film to us in a special theater in the observatory, and they played the audio of his call, and what I remember is that there was one additional “This is it!” past what everyone is used to hearing. Only his voice broke partway through, so it sounded to me more like, “This is…it…” and if I had to guess, I think that’s when he realized he was going to die.

              I climbed up to the top of the ridge and looked — I think it was roughly north, away from the volcano at any rate, and the next ridge looked about the same — scoured of vegetation. The ridge past that, every tree had been laid flat, with the tops pointing away from the volcano, loosely following the contours of the slope; no leaves, no branches, just charred black trunks. The ridge past THAT still held vertical trunks, but that’s all they were. Charred black fingers pointing into the sky, stripped of foliage and branches. They told me that that was because the speed of the pyroclastic flow was dropping with each successive ridge, and to a lesser extent, the heat — the trees were no longer blowing up.

              And I can readily believe that identifying trees as to species would be difficult, in the aftermath of all that.

              1. We went sometime between ’85 & ’88, after we were in Eugene, & after they’d opened the monument to the public.

                Even tho we saw the huge ash cloud, saw the bridges shut down due to the mud flow, scaled & id’d logs out of the blast zone. Had the education to intellectually visualize what had to have happened to the vegetation on the ground. Seeing the results at the ground was … well … Wow.

                1. Yeah, I know. Tell me about it. For all my study, all my research and education, you can’t know until you see it for yourself.

                  Then try to realize that a supervolcano eruption would be at least 3 orders of magnitude worse/more powerful.

                  And that it would put to shame the most powerful nuke the human race has ever managed to build and detonate.

                  It makes me feel…very small.

              2. Wow. I’ve only been on the Mt. St. Helens road once—I’m referring to the one that has interpretive centers all along, and none of them are the same. I’d like to go up that road again as an adult, but I’d likely have some kids along. (All of my kids have been to Lassen, and the oldest has been to Mt. St. Helens.)

                Side note: There ought to be a Volcano Path as a National Parks thing. Sort of like “collect the stamps”. Include Lassen, Crater Lake, Mt. St. Helens, and Rainier—and if they ever get a public access road in, Sutter Buttes as an example of a long-extinct volcano with no activity at all.

                1. I like the volcano trail idea, but seriously, it would be hard to know where to end it. I think I mentioned here (though it might have been on Facebook) that I have a mosaic photographic 360deg panorama from the top of a cinder cone near Bend OR. There are fifty some-odd mountain peaks visible in that panorama — and every one of them is a Cascade volcano. I was with a friend who lives in the Willamette Valley, and the whole region around her house is volcanic in nature. Heck, go out her back door, cross the horse pasture, wade the creek (excuse me, it’s a river out there), and have a look at the petrified log trapped in the lava flow, at the base of the volcanic neck comprised of columnar basalt. We sat on the lava-flow of a river bank, dangled our feet in the water, and sipped mint juleps while talking about the terrain. I’ve ridden her horses on trail rides over the Three Sisters. I saw more volcanoes on one trip to visit (and I’ve been several times) than I ever expected to see in my life.

                  That said, I’ve seen, lessee…
                  St. Helens
                  Three-Fingered Jack
                  Black Butte
                  Three Sisters
                  Broken Top
                  Pilot Butte (that’s the cinder cone from which I did the panorama)
                  Lava Butte (that’s the cinder cone from which I did the panorama)
                  Mazama/Crater Lake/Wizard Island/Scott

                  and a few others whose names escape me, and a bunch more that had no names to my knowledge.

                  1. …Yes, whenever I’m out there, I try to visit as many volcanic areas as I can. Had I not gone into astronomy/astrophysics, I would have become a geologist, and my principal interests were seismology/vulcanology. Ostensibly I have an undergrad minor and a grad subspecialty in geology, but practically I had more credits than was required for the minor, and the only thing that kept me from picking it up as an additional degree was the realization that I needed to get on with it and finish my education to start making an actual living doing all this stuff.

                  2. Heck you drive through lava fields on Hwy 126, Lake Cutoff out of Eugene, not to mention Old McKenzie Hwy 242 into Sisters.

                    I know of two lava tubes, one off Hwy 97 is huge & a tourist attraction not far from the High Desert Museum south of Bend. The other one is off 126 after hwy 20 meets up with 126 out of Corvallis, but it collapsed close to the entrance & now is blocked a few feet in.

                    Dee Wright Observatory made out of the basalt lava flow is up on the more level section of Hwy 242 just east of Scott Lake turn off. On a clear day you can see North to Mt St Helens. Don’t remember how far south you can see. You can see a dozen(s) (ish) of cinder cones & volcanic mountains of which all are marked on a disk at the top, plus out all the slit windows on the center section.

                    Newberry National Crater has Obsidian mounds & cliffs. Obsidian Falls is on the PCT South of hwy 242. The trail head access to the PCT for the falls is essentially Scott Lake. FYI. It is a steep trail climb & last time we were there (coming DOWN) the trail was a scramble over downed trees.

                    Waldo Lake trails, the trails off of 242 in both wildernesses, you wear boots, you put booties on your dog. Sharp lava rocks or sand (not so hard on feet) dominate the trails.

                    And none of this counts the basalt type cliffs you can find on the Oregon Coast along Hwy 101, or rather that Hwy 101 is carved on the side of.

                    Guess you can tell I’m local, and I grew up here, sort of take it for granted. Still not an expert. Spent my childhood more on the N. Umpqua while dad & grandpa fished. Or Eagle Creek while they hunted (NE corner – Baker). But the section of the PCT trail to hwy 242 to hwy 126 & north were favorite week long backpack hikes both just hubby & self & later with son’s troop. Plus we drove those roads between Eugene & La Pine then Bend where my in-laws lived, a lot.

                    1. My friends took me through several lava fields on various visits, but I couldn’t tell you which ones. One was off a major highway and a forest had grown up through it. I think that was near where we had a snowball fight in, like, June-ish, so it would have had some altitude.

                      My friends lived somewhere in the Eugene to Corvallis area. It was rural (because horses), and I forget the town that was their mailing address. He died some years back rather unexpectedly, and she’s been mostly incommunicado since. I’m pretty sure they were east of I-5 though. And I can’t find what I did with their mailing address.

                  3. That’s why I figure you limit the “stamp points” to National Parks/Monuments, and just do a representative sample of types. (Active with all types for Lassen, inactive super volcano with lake for Crater Lake, active most recently for Mt. St. Helens, and hasn’t blown yet for Rainier.)(Sutter Buttes isn’t National, but it also doesn’t have an access point yet.) I didn’t mean “trail” literally, since the Pacific Crest Trail pretty much covers the Cascades.

                    1. Hey. Roads are Trails. They just aren’t no-motor-vehicle Trails.

                      The PCT sections that don’t allow “wheels”, still allow feet as well as horse transportation.

                      Yes. PCT travels the base of a lot of the cascade range volcanoes. Most the others are visible from somewhere along the trail.

    3. Well, where it gets interesting is that a fan asked me in my biweekly Facebook Live Q&A how much bigger the KT impactor would have to be to reach Yellowstone supervolcano energy levels. After performing a few quick calculations, I informed him he had it backwards: how much bigger would, say, the La Garita supereruption need to be to reach Chixulub impact energy levels…Yellowstone wasn’t even in the picture…

      *Finds a nice big rock and hides*

      1. 😉 🙂

        My favorite T-Shirt that came out after the eruption was one depicting all the known volcanoes from the Canadian border down to at least Mt Lassen & Shasta. With Mt St Helens singing “Come on Boys & Girls … A one & a two & a Three … Lets Go!!!”

        😉 😉

  4. Adding “https://” (without the quote marks) at the beginning of the book link in this post’s page source should fix the link.

  5. I love poking around the volcanic areas all over the U.S.
    Even have a beautiful ring dike at Mt Ossipee, and a partial one at Mt Pawtuckaway in New Hampshire.

      1. I now once again live at the bottom of an ancient ocean, although I used to live on a glacial moraine.

        Volcanoes we don’t got. Except there were Precambrian ones up in northeast Ohio in “the Grenville Mountains”, and there’s maybe a giant extinct volcano circle on the SW Ohio-SE Indiana border.

        There are ancient ash beds of bentonite clay, too, but they came from ancient volcanoes in other states.

        1. We managed to find both. Our area had volcanoes going through the seabed, so what we consider our “soil” is X quantity of pumice over Y quantity of shale. In the hollows, there can be 5′ of pumice, while on the ridges, an inch or 6 at most. All this is seasoned with a sprinkling of obsidian, ranging from 2″ diameter balls to “I don’t have the equipment to try to find out”.

        2. The Grenville Orogeny was a mountain-buiilding period during the formation of the Rodinia supercontinent, which you might remember from Rock and Roll: The New Madrid Fault Zone. Rather a widespread event, with evidence on multiple continents — it is known as the Dalslandian Orogeny in Europe, and the Kibaran Orogeny in Africa. The Grenville runs from Labrador in Canada, diagonally across the North American craton into Mexico, almost to the Gulf of Baja, with additional pieces showing up along the Bay of Campeche.

            1. Rodinia, actually. As the continental plates came together, a subduction zone formed. This probably resulted in significant seismic activity and possible tsunamis, and did result in volcanism of the type now being seen in the Cascade Range (and was thus responsible for the volcanoes mentioned by another commenter). The Grenville Orogeny created what we could think of as Appalachians 1.0, some of which can still be found today in the Long Range Mountains in Newfoundland, parts of the Adirondacks, the Canadian Shield, and the massifs of the Blue Ridge Province of the mid-Atlantic states region.

              And the breakup of Rodinia resulted in numerous failed rift systems, including the older Keweenawan Rift, and the Reelfoot Rift, both of which nearly tore the North American craton in two, and the latter formed possibly the most dangerous fault zone in North America: The New Madrid seismic zone. This, coupled with the associated Wabash Valley seismic zone and the Southern Oklahoma Aulacogen, which is a similar rift formed at the same time and for the same reasons, results in significant potential for destruction in the center of the continent, even today.

      2. Used to go hiking on Mt Rainier frequently when I was stationed at McChord. Been to Lassen, Crater Lake, Craters of the Moon, Shasta, Yellowstone, Obsidian Mt, that cute cinder cone by Flagstaff Az, the one you see off the north side of the highway. Amateur geologist, rockhound, and spelunker. Kind of a shame the number of places you used to be able to collect rocks and minerals has drastically dropped over the past 50 years. Destroyed by development, posted due to liability, or posted due to bad people leaving trash or even blowing up the sites, and in a couple of rare cases, reopening commercially.

        1. I haven’t hit all those, but I’ve prowled the volcanoes in Oregon; I used to have friends who lived there and “did” horses, so I’ve both hiked and/or horseback ridden over a goodly part of those. The area around Bend was startling for this woman who lived most of her life in/around the Tennessee River Valley — I have one mosaic panorama from the top of a cinder cone near Bend, with some 50 peaks in the imagery — and every one of them a volcano. Not one fold or fault-block mountain in the lot.

  6. It looks like there’s a factor of 100 between index 1 and index 2, which seems weird, as all the other factors are 10. Do you know why that anomaly’s there? I’d have thought they could have put promoted all the steps higher than 1 and put in an extra step to get x10 factors all the way up.

    A few years ago I read Harry Turtledove’s Supervolcano series, which was kind of in bestseller style rather than hard SF style, but which I still found enjoyable.

    Now I want to figure out how many dice of damage that equates to in GURPS. . . .

    1. No idea why the difference, unless the natural eruptions just jump that far. I wasn’t involved in the development of the scale, so I got no clue.

      And I was unfamiliar with Turtledove’s series; I’ll have to go check it out.

      1. Give yourself lots of time and clear out some mental storage to keep track of the 40 zillion characters, each appearing once every 400 pages or so. He gets paid by the word, and writes like it.

        1. That wasn’t nearly so bad in this series. The important characters were a cop and his partner; his ex-wife; his new wife, a vulcanologist; his three kids; his older son’s band; his daughter’s former boyfriend and his wife, and his daughter’s post-catastrophe boyfriend. That’s about a dozen.

      2. And be prepared to facepalm at the rapidity said volcano goes from “huh, interesting” to “Holy sheep!”

      3. Well, it looks like I’ll have to start the GURPS scale at level 2 being 6d x250, with another x10 for each two added steps. That would cost a lot of points, but then gods or superbeings who can cause volcanic eruptions ought to cost a lot of points.

  7. There’s a movie about Yellowstone erupting, called (what else) Supervolcano. My Lady likes it, and which I’m kinda non-plussed by disaster movies, he taste is usually pretty good. Not sure if you can get it legit now. When we stumbled across it we had to burn our own copy.

      1. Well, enjoy it. Just don’t take it remotely seriously. I have yet to see one of those that comes anywhere close to being realistic. They all tend to be bombastic and sensationalistic.

      2. Oh yeah. The Flat State U geology department did a special showing for their “Bad Science Movie” night. You know, groan at the errors, throw popcorn at the cheezy love scenes, root for the San Andreas fault, that kind of thing.

  8. Good read, and I’m not surprised to find out that Yellowstone was only considered a supervolcano fairly recently. It’s still one of the places on the planet I want to visit though.

    My interest in volcanoes dates back from childhood; I will admit that part of it was fueled by that scene in the first Fantasia where they depict the early Earth and stages of evolution, through to the death of the dinosaurs and the colliding of the continental plates. Then there was finding out that Taal Volcano had those nesting doll crater lakes… and later the Mt. Pinatubo (whose name I always chuckled over; ‘let (it) grow’) ) eruption.

    David Attenborough’s Life On Earth was also an influence, as I vaguely recall a section about life near undersea vents, which was fascinating to me.

      1. Yup, yup, yup, yup, and yup.

        But then, caldera eruptions tend to do that anyway. The major eruption empties the initial magma chamber, which collapses, rather like a sinkhole (and for the same reasons; substitute “magma” for “water” and you have it), only the melt keeps coming up and rebuilding the eruption cone/resurgent dome in the middle of the caldera, which has been collecting water meanwhile. When another massive eruption blows the top out of the dome and it partially collapses to form a caldera within the original caldera, and the magma keeps flowing, creating ANOTHER dome, which blows…

        You get the idea.

        As long as the vent supplying the magma stays in the same place with respect to the original caldera-forming eruption, you can get those concentric calderas like that.

        But it doesn’t always…
        *shameless foreshadowing*

        1. Hence the series of extinct volcanos that make up the Snake River Valley and end at Yellowstone.

          Ugh. Now I’ve got the notion of a link between the Columbia Plateau lava flows and the Yellowstone hotspot. Have to go look up the timing of those events.

          1. We’ll talk about the Snake River Valley.

            And you’re not the first one with that idea. There is a good bit of debate about whether nor not the Columbia Traps were associated.

          2. The notion is almost certainly correct.
            Proving it is a bit of a problem. There’s lots of circumstantial evidence, and there are circumstances that can reasonably explain the shift, but…

            (Shrug) Before the hotspot came through, the Idaho Batholith almost certainly extended well into Nevada. But there’s really no way to prove that. Similar chemical composition intruded at a similar time only gets you so far.

          3. There is some overlap. The earliest Columbia basalt eruptions began over 17.5 million years ago, and the oldest caldera in the Yellowstone/Snake River chain is roughly 16 million years old. They are probably close enough to share the same source, and the Steens Mountain fissures are fairly close to the oldest McDermitt caldera eruptions. The timing is offset, with the basalt flows occurring before the rhyolite caldera forming eruptions. The differing eruptive styles are probably due to whether the rising magma penetrated thick continental granite or thinner accreted island arc crust. This area is close to where the old edge of the continent was. The basalt eruptions migrated to the north and a bit east (that is where the vents were, the lava flowed mostly west}, peaking between 17-15.5 million years ago. The rhyolite eruptions formed calderas mostly eastward and a bit north and eventually formed the Snake River plain.

            Note: an earlier post disappeared when I tried to send, this one is better 🙂

        2. *blink… blink… blink…* dang it. You just plot bunnied me on a story that’s been bugging me (fortunately setting not event). Now to do math on a caldera the size of Australia and what other geological processes I need. If only to get the idea out of my head. (Side note, a long time ago I promised you some information on interior continent magnetism of the near surface. The original conversation revolved around the Carrington event. I have not forgotten, the information is just proving harder to find than I expected.)

          1. THE SIZE OF AUSTRALIA?!?!?! No, hon, I’m sorry, unpossible. I don’t even know where you would get that much melt in one place. Or how. That’s a Krypton-detonation kinda event. And THAT was unpossible.

            1. I know. Hence the ‘if only to get the idea out of my head.’ (Which, in retrospect was far more clear to me than it was likely to be to anyone else, my apologies.) On the other hand doing the math won’t be an entire waste of time, beyond just getting the notion out of the claws of my muse.

              1. Oh. Well, that would work, I suppose.

                Tossing a more realistic problem your way, see if you can calculate how big an asteroid would be required to create an Australia-sized crater, and how much energy it would release. (Feel free to choose the asteroid’s composition, hence density.)

                Why yes, I have taught at the college level. Why do you ask?

                And yes, I know that that’s hugely much bigger than the Chixulub impactor, and is a planet-killer.

                1. Ooo. More math problems. 🙂 I’ll take them, they take the ‘what if’ part of my brain and keep it from getting too out of hand. (I only have a bachelors in the rocks.) I’m working out the geology of a weirdly shaped continent. (Circular, with a large and largely circular sea offset from center making the land crescent shaped.) And I’ve been trying to figure out if it would work geologically. (Probably not, but the the plot bunnies keep coming, and only math kills them.)

                  1. UofA (I think) has an on-line impact effect calculator.

                    Played with it when I took Planetary Sciences for non-majors when I made my second run at my degree.

  9. Were there colliding plates in Fantasia? It was released in 1940, and my memory is that plate tectonics was just being accepted when I was in college in the 1960s. Of course continental drift goes back a ways, but it was kind of speculative.

    1. *chuckle* That’s how I interpreted the sudden mountain-like rocks (they looked like mountains to me) pushing out of the ground, not necessarily what they were portraying. I did watch the thing as a 3-4 year old, in the 80s.

      Kind of the same way that kids these days watch Dora the Explorer or Peppa Pig repeatedly. I suppose my parents got off lucky that they only had to tolerate repeat performances of classical music.

    2. Somewhere in the ’60s, I read *something* that mocked the idea that continents can move, and any similarity between South America and Africa’s coastlines was purest poppycock. Besides, how are you going to get basalt to move around? Stuck in my memory; I think it bothered me at the time…

      Wish I could remember the source. It would have been great for one of those “the science is settled, you deplorable denier!” arguments.

      Reunite Gondwanaland!

        1. I remember looking at a globe when I was a kid in the mid-70s (I was probably about 4?) and thinking “South America and Africa look like they kind of fit together” and my mother telling me “Some people think they used to be next to each other, some people don’t.”

      1. Search term for you: “Eugeosynclinal Theorum” Basically, when ocean mapping became possible because of advancements in sonar, they finnaly could test the expectations, for Eugeosynclinal Theorum it went ‘Ok if this is right we will see a continuous remnant of mountains between Nova Scotia, Iceland, and Scotland.’ And then they got there and went “Why is there a mountain range in the middle of the Atlantic ocean? What the actual f*?” It wasn’t until the 70s that tectonics was really starting to be taught as ‘how things actually worked’ (my dad was getting HIS geology degree at the time and remembers a lot of the new-and-shiny. I learned about Eugeosynclinal Theorum in my tectonics course as more of a ‘history of the field’.) I’ve got a textbook somewhere about from the latish 60s where they were making the transition and it’s quite interesting. And a good reminder that these things rarely happen all at once.

  10. I remember one year the Yellowstone newsletter featured questions the park rangers had been asked. My favorite was “What is the park doing to prevent future eruptions of the Yellowstone volcano?” 😀

    1. I believe that to appease the spirit of Yellowstone, the National Park Service has decided to start sacrificing morons who harass the wildlife, throwing their moronic carcasses into the thermal features. There’s a reason that since his arrest, you haven’t heard word one about the guy that had been caught on video taunting the bison from fifteen feet away. 😛

          1. What, jumping into geysers, bathing in hot springs, and walking on hot rocks that will sear your face off? Or bathing in acidic or basic mineral ponds that will sear your face off?

      1. Last year, the bison in Yellowstone and Grand Teton managed to collect 10 dumb tourists for their wall mounts. Not sure if that was the record, or if there was a contest to see who could contribute the most to the Darwin Award counts.

    2. On slightly more sober reflection though, when people are taught these days that humanity can alter the planet’s weather to a permanent degree, or for the matter, that Israel is responsible for (insert natural disaster here), the idea that ‘humanity can also control the planet’s (insert thing here)’ seems only stupid to the people who are informed enough about REAL science to know better.

      I see anthropogenic global warming as something not too dissimilar to Pol Pot’s “glasses = educated people”; an excuse to call for the executions of other people / tell other people not to breed / call for ‘voluntary extinction for the good of the planet.’

      Anthropogenic warming in a local scale, sure. Around a large city, the surrounds, and perhaps China and India, or areas of very dense population. Global, not so much. (My general response to ‘ERHMERGERD CO2’ was usually “Plant more greenery, they’ll love it.” – granted, based off of my childhood awareness of the basic CO2->plant->oxygen cycle.)

        1. That would require an education or mind untainted by women’s and gender and social justice studies. Also, studying history, which would require acknowledging that people in the past did stuff right, without their ‘brilliant, modern thinking.’

      1. My favorite idea to fix Yellowstone – Drill down to the chamber and relieve the pressure so it will not explode.

        Can You say TRIGGER?

        Want to attack earth but make humans think you are saving them.
        Take 3 rocks and hit 3 supper volcanos spaced around the world.
        Wait a week and then arrive and say you were passing by and just could not leave with out helping, even if there are laws against it.

        Only one real problem. There are enough of us that KNOW that 3 rocks are not setting off SVs at the same time by accident.

        1. *tries to avoid the gigglefit so I don’t wake the other person sleeping in the room*

          Oh Gods. If only the first thing that came to mind WASN’T that idiotic, self-absorbed full of fake and mental damage Brianna Wu and her ‘you could throw rocks from the moon’ weaponizing space hysteria.

  11. “Valles Caldera, Santa Fe, New Mexico, USA”
    Is about 15 miles as the crow flies from my house. First time I knew I lived near a super Volcano. Been there many times. It’s a lovely, and twisty, drive up from Los Alamos.
    The other interesting feature near my house (a mile or so) is the lava plug that was ejected the last time it erupted a couple of million years ago. It’s one of the somewhat numerous “Black Mesa’s” in New Mexico.
    Although it’s considered “dormant” there are numerous hot springs in and around the caldera. Been to a bunch of those also. Los Alamos National Labs test built a geothermal electric plant, visible on Google Earth at 35 52 47.05 N 106 40 26.73 W..

    1. Yeah, whenever the lava plug from the previous eruption is thrown out of the crater and forms a feature that comes to be called “X Mesa” or “X Butte,” chances are, you might have a supervolcano in the area.

      As Jeff Foxworthy would say, “Here’s yer sign.”

      …Actually, the sign is the mesa, but hey.

    2. It is a beautiful place. We visit it about once a years. But its location is much nearer Los Alamos than Santa Fe.

      1. True. Except most people know about where Santa Fe is located. Not many know Ponderosa (the actual closest town) or even Jemez Springs (the address of Valles Caldera National Preserve). The actual caldera is located in Sandoval County, west of Los Alamos county.
        Much of the area surrounding the caldera is made up of tuff, which is a soft rock that’s essentially compressed volcanic ash. Quite interesting because the horizontal bands of rock are all different colors, primarily whitish and reddish. And because it’s so soft many of the prehistoric native Americans carved caves out of the rock (which they lived in), many of which can be seen from the highways to Los Alamos and White Rock. Bandelier National Monument has some very good examples.

  12. Did you ever see a video of a bullet hitting a bottle or a balloon, in super-slow-motion? The bullet hits one side. A few microseconds later, the pressure through the water (water is incompressible) is propagated THROUGH the balloon, and the opposite side from the bullet impact begins to bulge out.

    Now imagine the effect of the “dinosaur killer” asteroid or even a larger impact striking the Earth. The pressure THROUGH THE CORE ought to be strong enough to shatter the crust on the opposite side of the Earth. And please note that the Deccan Traps are on approximately the opposite side of the Earth as the Chicxulub impact site, and the approximate time is actually fairly close to 65 million years ago.

    So I’m suggesting that the various “traps” locations around the Earth are approximately opposite locations of impact sites. And since oceanic impact craters are generally hidden by the seas, this might be a way to locate previously-unknown impact locations from eons ago.

    1. That’s not a new concept by any means, and yes, there is a contingent of geologists who believe the Deccan Traps are the antipodal response to the converging shock waves from the Chixulub impact. In fact, there are apparently enough to support the theory and spark some research.
      (Ex.: )

      But there are other known impact sites whose antipodes do not seem to have traps. This may be because plate tectonics have carried them elsewhere — which actually argues AGAINST the Deccan Traps being a response to Chixulub. For instance, the biggest impact structure known on Earth is the Vredefort crater in South Africa; it’s antipodes would be around Hawaii. But the Hawaiian chain is known to be produced by a small mantle plume, and there is no sign of traps in the sea floor surrounds. More, the impact is estimated to occur some 2 billion years old, and that encompasses a lot of plate tectonics, and no less than FOUR supercontinental formations and breakups.

      In other words, it’s an interesting concept, but kinda hard to prove.

      1. Good to know that I’m not entirely crazy to think that!

        It took Luis and Walter Alvarez over a decade to have their hypothesis of the KT extinction generally accepted. I would suggest that many of the mass extinction events in the fossil record might be impact-caused. For example, has anybody looked for a potential impact event associated with the Permian extinction of 250ma?

          1. It’s important to remember that erosional forces and tectonics combined tend to erase any evidence of impact older than a certain amount, meaning the “smoking gun” would be mostly to wholly destroyed, even “recycled.”

            1. I vaguely recall my geology classes including mention of some of the rare earth (or possibly rare metal) deposits in South Africa being dated to one of the major extinctions and theorizing it’s what’s left of a major impact. Unfortunately brainy no worky this morning so that’s as far as I can go.

              1. Yes, that’s much speculated.

                More, I think that might be where the Marvel writers got the idea for vibranium in Wakanda. Not sure. Haven’t heard any specific scuttlebutt about it, but when I saw that bit about the ancient impact crater (dang near 200mi across, if memory serves) and possible ore bodies in my research, it’s one of the first things I thought of.

  13. You know, since this blog seems to have an appreciation for sci-fi, as well as volcanoes, well..

    How about some on-topic sci-fi progressive metal.I hope this link comes through..

    Yellowstone Memorial Day by Arjen Lucassen, with an opening from Rutger Hauer.

  14. “If we scale the blast size up proportionally, this would result in a blast equivalent to approximately 700 MT to 7 GT.”

    But can the blast mechanism scale up to that level? ISTM that the magnitude of an individual blast would be limited by the material properties of the rock involved. AIUI, the mechanism is release of steam pressure when it exceeds the strength of the overlaying rock. To get a big explosion, there has to be a large reservoir of steam, which means a large area of rock which all resists the pressure up to an explosive level, then fails across the whole area at once.

    ISTM that above a certain size, there would be local failures rather than one earth-shattering kaboom.

    1. Oh, there are several important things to realize in the course of all of this.

      1) This is only part 1 of a 5-part series; there is considerably more info to impart.

      2) There is even more info in the ebook than I could reasonably cram into a blog series and have it make sense, without readers flipping from article to article. (Besides, Amazon gets POed if you put too much of the book into other media.)

      3) There are far more concerns in terms of pressure from the tremendous quantities of gases dissolved in the melt. This is the true source of the eruptive power, not a steam explosion. These gases do include water vapor, but this may be equaled or even exceeded by carbon dioxide, sulfur dioxide, hydrogen sulfide, and more. Here’s a fairly decent rundown of what you could expect, with variations depending on the chemical composition of the melt at any given eruption:

      4) A supervolcano eruption is NOT one “earth-shattering kaboom,” but a titanic release of energy over what can be a very long or relatively short timeframe. While it is convenient to compare it to the energy of a nuclear weapon because of the scale of the energy, the two do not readily compare otherwise. A nuke releases its energy in a fraction of a second; a volcano — even a supervolcano — in hours to days to weeks. There is a sequence of events that occurs heralding and during an eruption, which is too long to go into here. The lead-up steps can take decades to millennia or longer. Past a certain point, however, matters proceed apace, and the eruption itself will occur in a matter of moments. But the energy will continue to be released for as long as the eruptive phase continues. Look at Kilauea, which has been in more or less continuous eruption for literal decades. The current East Rift Zone eruptive phase has been going on since early May, or over 3 months now, and has only slowed down in the last couple of days.

      Now, what you’re referencing is indeed a thing; it’s called a hydrothermal or phreatic eruption, and they happen a fair amount. I have myself been present for numerous phreatic eruptions of Mt. St. Helens. However, generally what is happening in such an eruption is that the local groundwater is superheated and then something happens to release the pressure; it flashes to steam and blows the rocks around it away. When this occurs along a vent to produce a fountain of boiling water, it’s called a geyser. Many of the “explosions” at the Kilauea summit during this current eruptive sequence have been as a result of the magma apparently draining off through the eastern rift, dropping the level in the magma pool of the central caldera and allowing groundwater to seep in. You get a boiler explosion, it flings some ash and chunks of rock into the air, seismic stations register it as about a 5 (St. Helens was a lot smaller), and that’s about it. And that’s not even occurring where the lava is being extruded.

      Hydrothermal eruptions are the most common type of “volcanic” eruption there are, but they don’t involve lava extrusion at all. They can leave decent-sized holes in the ground (“craters”), and sometimes those fill with water — Mary Bay on Yellowstone Lake is actually the crater of a hydrothermal eruption — but it isn’t gonna produce a supereruption. Or even a regular eruption, for that matter.

  15. I know this is an excerpt, but I would have liked the list of dormant supervolcanoes to have Google Earth links.

  16. Different subject FYI: Last week someone commented and ran down NASA for wasting money and not bothering to study the Sun. With luck, tonight NASA will launch the Parker Solar Probe, about which more here:

    Do also please note the left sidebar, where it says:
    Related Topics:
    SDO Solar Mission
    Space Weather

    FWIW, defining acronyms:
    SDO – Solar Dynamics Observatory
    SOHO – SOlar and Heliospheric Observatory
    STEREO (there are 2 of these) – Solar TErrestrial RElations Observatory

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