It is like finding a leak in your roof. I remember once up at the cabin, noticing that my waders were full of water and pointing this out to my wife.
“You’re supposed to hang the waders upside down. Keeps dead mice from falling in there.”
Well, I thought, if any mice fell in these waders and weren’t dead, they’d drown for sure. Anyway, I traced the leak to a part of the ceiling in the closet. Eventually I was able to find the place in the attic where the water was probably going down into the closet, but by this time the torrential rain storms that had preceded the discovery of Lake Waders had long passed and I was going on indirect evidence. Over the next few weeks there were more storms, and every now and then I got to look at where the leak was tracing from but always lost track of it.
Finally, my father-in-law and I figured out how to do it. I got up on the roof with a hose, and he got in the attic with a flashlight. I kept pouring water and he kept tracing back drips until we finally found the perfectly round hole, hidden from view at the top by some recently grown lichen. It was an exit wound, like a .22 caliber bullet had exited the roof in an accidental discharge. Or maybe it was an entrance wound. Eventually I decided it must have been a meteor. No particular evidence for that, but it would be the coolest explanation.
Anyway that’s how it has been over the last few decades at Yellowstone.
You know Yellowstone is one of the world’s largest calderas. When it was formed, in a major explosive eruption about 650,000 years ago or so, it must have been a hell of a mess. If something like that happened there again it would totally ruin the day for anybody visiting the park. And, by “visiting the park” I mean living anywhere in North America pretty much.
Early on, Geologists knew there was a magma plume. This is equivalent, in my analogy, to the big rainstorm that provided the water for the leak in the roof. We know it is there because you can see it. As the North American continental plate moves along to the southwest, it passes over the plume, and the plume is the source for lots of volcanic activity including the occasional day-ruining super volcanic caldera eruption, the big Yellowstone eruption being the most recent of those. You can see all the older volcanic activity, and date it, in a somewhat curved line passing upwards in time along the surface of the continental plate. No problem identifying that.
But, how does the surface of Yellowstone, which puts enormous amounts of volcanic CO2 into the atmosphere continuously, has the largest hydro-thermal system on the planet, the occassional lava flow, etc. connect to the lava plume?
A while back scientists used seismic imaging to depict a fairly large and complex magma feature under the surface. This provides the immediate heat and gasses, but it was not large enough or deep enough to be the ultimate source or the connection to the deeper mantle of the earth. They were still in the attic trying to trace back the leak.
Now, scientists Hsin-Hua Huang, Fan-Chi Lin, Brandon Schmandt, Jamie Farrell, Robert B. Smith, Victor C. Tsai, in a paper titled “The Yellowstone magmatic system from the mantle plume to the upper crust,” published in Science, have used even more seismic imaging to locate and map out a deeper, larger batch of magma that is the link between the molten hot deepens of the earth, the part under the continental plates, and the Yellowstone area.
From the Abstract:
The Yellowstone supervolcano is one of the largest active continental silicic volcanic fields in the world. An understanding of its properties is key to enhancing our knowledge of volcanic mechanisms and corresponding risk. Using a joint local and teleseismic earthquake P-wave seismic inversion, we unveil a basaltic lower-crustal magma body that provides a magmatic link between the Yellowstone mantle plume and the previously imaged upper-crustal magma reservoir. This lower-crustal magma body has a volume of 46,000 km3, ~4.5 times larger than the upper-crustal magma reservoir, and contains a melt fraction of ~2%. These estimates are critical to understanding the evolution of bimodal basaltic-rhyolitic volcanism, explaining the magnitude of CO2 discharge, and constraining dynamic models of the magmatic system for volcanic hazard assessment.
I love the use of the word “unveil” here. “Hey, Duane, I think I unveiled a bullet hole up here on the roof! There’s your problem!”
Anyway, the details are strikingly complex and involved intense geological science. The implications are still a bit unclear. In a write-up by Eric Hand in Science, geophysicist Alan Lavender says this is “a comprehensive view of the magma system from the top of the plume into the crust. [But] this doesn’t exactly match up with our expectations.” Scientists had been expecting the offset between the upper and lower chambers to be in the opposite direction, west rather than east of the plume.
I don’t know. Maybe they were just holding the map upside down. They need to stick a pencil through the hole to verify it as the true source, like Duane did while I was up there on the roof.
Caption for the image at the top of the post:
Fig. 4 Schematic model for the Yellowstone crust-to-upper mantle magmatic system.
The orientation of the model is along the cross-section AA? in Fig. 3. The geometry of the upper and lower crustal magma reservoirs are based on the contour of 5% VP reduction in the tomographic model. The dashed outline of the lower crustal magma reservoir indicates the larger uncertainties in its boundaries relative to that of the upper reservoir (25). The white arrow indicates the North American plate
Calbuco is a volcano in southern Chile. This one erupts fairly frequently averaging about every 20 years, sometimes quite impresively. The largest eruption during historic times in Chile occurred at Calbuco in 1894.
It is erupting now. Evacuations have been ordered. Here is some amazing footage:
One wonders if anyone felt it. Did Charlemagne feel it as he led his forces across Pagan Saxon Westphalia, knocking down Irminsuls and making everyone pretend to be Christian or else? Did the people of Bagdad, just becoming the world’s largest city, notice anything aside from their own metro-bigness? Did the Abbasid Caliph Muhammad ibn Mansur al-Mahdi have the impression something cosmic was going on that year, other than his own ascendancy to power? Or was it mainly some of the Nitrogen molecules in the upper atmosphere that were changed, not forever but for an average of 5,730 years, by the event?
A long time ago, probably in our galaxy but kind of far away, a cosmic event happened that caused the Earth to be bathed in Gamma rays in AD 774 or 775. No one seems to have noticed. There is a mention, in 774, of an apparition in the sky that could be related, but talk of apparitions in the sky were more common back then, before they had certified astronomers to check things out. There is chemical and physical evidence, though, of the Gamma ray burst. The best evidence is the large scale conversion of stable Nitrogen isotopes into unstable Carbon–14 isotopes in the upper atmosphere. As you know, radioactive (meaning, unstable) Carbon–14 is created continuously but at a somewhat variable rate in the upper atmosphere. Some of that Carbon is incorporated, along with regular stable Carbon, into living tissues. After the living tissue is created and further biological activity that might retrofit some of the Carbon atoms ends (i.e., the thing dies) the ratio of radioactive Carbon to stable Carbon slowly changes as the radioactive Carbon changes back into Nitrogen. By measuring the ratio now, we can estimate how many years ago, plus or minus, the originally living thing lived and died.
But it does vary. Solar activity, nuclear testing, other things, can change the amount of Carbon–14 that gets produced. And, a cosmic event that happened in 774/775 caused the production of enough Carbon–14 to throw off the chronology by hundreds of years. This is seen in the close examination of Carbon in the tissue of trees placed in a tree ring chronology. For example:
Original Caption: High-resolution radiocarbon ages, superimposed on annually resolved radiocarbon measurements from Japan and Europe (grey lines and crosses) as well as the IntCal calibration curve based on decadal samples (blue shading), re-sampled at 5 year intervals (light blue crosses). Radiocarbon ages (that is, using 14C, 13C and 12C isotopes) were determined at ETHZ with the MICADAS system.
See the inverted spike there? That is, apparently, gamma rays messing up the Radiocarbon chronology. Hold that thought.
Climate Change Is Hard
When volcanoes erupt, they typically spew crap into the air. Some of this material stays in the atmosphere for a while (called aerosol, but not your underarm deodorant exactly) which will in turn reflect sunlight back out into space prematurely. This causes cooling. It is essential to know how much cooling of the atmosphere happens from aerosols because this is a potentially important factor in global warming. The effect of aerosols caused by volcanoes or industrial activity is an important term in the big giant equation that puts all the different factors together to produce global warming (or cooling). It is important that climate models be able to accurately and realistically incorporate the effects of aerosols. If the science isn’t right on aerosols, climate models may not run true when aerosols are included.
And indeed there is an apparent problem. When climate models are run and include aerosols, and the results are compared with real life data where we have good proxyindicators of past climate, the model predictions and the real life measurements don’t line up when aerosols are involved at any significant level. A big volcano goes off, but the proxy record consisting mainly of things like tree rings doesn’t show the level of cooling models predict. This has titillated denialists, as you might imagine, because it shows how the science has it all wrong and the only way to truly understand the climate change is to spend hours in the basement with your spreadsheet and a good internet connection, like Galileo would have done.
In fact, this was an interesting problem that needed to be addressed. The modeling methods had to be wrong, or the paleodata had to be wrong, or something had to be wrong.
In 2012 Michael Mann, Jose Fuentes and Scott Rutherford published a paper in Nature Geoscience proposing a hypothesis to explain this discrepancy. The problem was that when a known volcano went off, the tree ring record in particular tended to show only an anemic result. Volcanoes that were thought to totally mess up the weather seemed to have little effect on trees. This even applied to volcanoes which were very directly observed in recent times, when we know there was an effect because people were putting on sweaters and measuring things with actual thermometers.
Mann et al proposed that rather than having little effect on tree growth, the volcanoes had a huge effect on tree growth. What was being seen by the Dendrochronologists (tree daters, like tree huggers but more serious) as a normal, average growth ring at the time of a volcanic eruption was actually the ring for the next year in line; they were missing, understandably, one or more growth rings. The volcano goes off, the trees don’t grow at all. (The masquerading ring would typically be the year before the missing ring since dendrochronology is done backwards, since we know what year it is now.)
You don’t have to imagine a year in which no tree grows ever anywhere to accept this idea. The trees being used as temperature proxies are more the sensitive type. They respond to temperature changes by growing more or less (warmer vs. cooler). Trees that don’t do this are not chosen for study. This has to do with the species and the setting the tree grows in, combining to make temperature the key limiting factor most years, so that growth ring width reflects temperature more than any other factor. So yeah, when it gets very cool because of a big-ass volcanic eruption, one of those “year with out a summer” deals, the very sensitive trees respond by not growing at all that year. They may have a growth period of a few weeks, but trees don’t simply lay down wood every day they are biologically acvite. They usually start with leaves, then many move on to reproduction, and once they have finished reproducing, have a cigarette, wash up, whatever, they may lay down wood or roots. (Different species have different patterns). So a very short growing season can mean no ring at all. If a really bad nuclear-winter-esque volcano happens this may go on for a few years. This leads to the growth ring corresponding to the year of the volcano simply not being noticed by the dendrochronologists, with a different year standing in. Over time the record can be thrown off by several years, if there are a few volcanoes and one or more of them affects growth for more than one year.
So two things happen. Years with a very strong cold signal are lost entirely, and the record is quasi-randomly offset by a few years in some but not all tree records (because some will be thrown off while others are not) so the collective record gets out of alignment. A strong uptick in the signal (the zero growth year) does not contribute to the paleoclimate squiggle of temperature at all, and the other possibly contributing years (after the worst is over) are moved around in relation to each other and average in with less cold years. It’s a mess.
Consider the following made up numbers representing temperature over time. The top table is the hypothetical raw data of tree ring growth in relation to temperature across a very strong cold anomaly as might be caused by a massive volcanic eruption. Depending on the tree, there is one or more years of zero growth. The lower table is the same set of numbers but with the earlier years (top) shifted down to cover the zeros, because that is what would happen if a dendrochronologist was looking at the rings from more recent (bottom) to oldest; there would just be this void and it would be filled with the next data in line.
Here are the same data graphed showing a clear anomaly in the top chart, but the very clear anomaly utterly disappears because of missing rings and shifting sequences in the lower chart. This is an existential problem for ancient climate events. I squiggle therefore I am.
Mann Et Al proposed adjustments to the record of proxyindicators of temperature that accounted for missing tree rings at the time of major volcanic events. They made a good case, but it was a bit complicated and relied on some fairly complicated modeling.
Since the publication of Mann et al there has been quite a bit of back and forth between the climate modelers and the dendrochronologists. I’ve assembled a list of publications and blog posts below. I’ll only very briefly summarize here.
The dendrochronologists had a bit of an academic fit over the idea that they had missed rings. Understandably so. As an archaeologist, I’m partly trained in dendrochronology. There was actually a time when I considered making it my specialty, so I had read all the literature on the topic. I can tell you that missing rings was a serious concern, and taken seriously, and seriously addressed. Seriously, there’s no way modern dendrochronologists would totally miss an entire year’s growth rings. They had ways of dealing with missing rings.
The thing is, it is actually possible to miss rings. Here’s why. The assumption in Dendrochronology is that rings can be missed (or for that matter, added) for reasons that allow for correction by cross dating growth ring sequences with other trees or even other samples in a single tree. A particular part of a tree can be missing a ring while another is not (especially vertically; the lower part of a tree grows last in many species), or some trees in an area may be missing a ring, but others have that growth ring. This assumption is probably almost always valid; missing rings can ben adjusted for by cross checking across samples. But, if all of the trees of a given species and sampling area have one or more missing rings because of a major volcanic event, that won’t work. But this is not something Dendrochronologists are used to.
2 + 2 = 774/775
Eventually Mann and his Colleagues put two and two together and realize that the Dendrochronologists had a way to test the hypothesis that would not rely on fancy dancy climate modeling techniques, and that would potentially allow a better calibration of the tree growth ring record for certain time periods. It was that Gamma ray burst.
That moment in time is a clear marker. Any system involving Carbon–14 spanning this time interval should show the spike. Well, what about tree ring records that span both a major volcano and the 774/775 event? If Mann et all are right, an uncorrected tree ring record would show a lack of correspondence of any spike at 774/775. But, if missing rings are assumed for sensitive tree records at the time of the volcano, and the tree ring sequence for those trees shifted, perhaps the records will line up. That would be a test of the hypothesis.
And this is the gist of a letter to Nature from Scott Rutherford and Michael Mann. Very simply put, Mann and his colleagues took this graph, from an earlier paper:
And changed it to this graphic which shows mainly (see caption) the tree ring sequences that span both the 1258 volcanic eruption, which was a big one, and the 774/775 event.
This is a gauntlet, being respectfully thrown down. Mann et al erected a hypothesis, that missing tree rings are virtually universal in large parts of the dendrochronological sample for some events, were not accounted for in the tree ring chronology, and have thus messed up the tree rings as a proxyindicator for temperature. Various attempts to knock it down have not worked out. Now, Mann has himself provided an excellent way to assail his own idea. It is now up to the tree ring experts to try to knock this hypothesis down. I suspect Charlemagne might have had an easier time knocking down the Irminsul.
I asked Michael Mann how he felt about this latest development in the ongoing saga of the missing (probably) growth rings. He said, “I’m very pleased that we’ve reached some level of reconciliation with our dendroclimatology colleagues: there’s an objective test that is available to determine if there are indeed missing rings in some of the regional chronologies as we have speculated to be the case. I look forward to seeing the results of those tests. We proposed a hypothesis, other scientists were skeptical of the hypothesis, and now there is a way forward for testing the hypothesis. In the end, a fair amount of good science will have been done, and we will have learned something. This is the way science is supposed to work.”
This is going to make a great Master’s thesis for someone.
As promised, a list of writings on this topic, organized by date:
2012 (November) Kevin J. Anchukaitis, Petra Breitenmoser, Keith R. Briffa, Agata Buchwal, Ulf Büntgen, Edward R. Cook, Rosanne D. D’Arrigo, Jan Esper, Michael N. Evans, David Frank, Håkan Grudd, Björn E. Gunnarson, Malcolm K. Hughes, Alexander V. Kirdyanov, Christian Körner, Paul J. Krusic, Brian Luckman, Thomas M. Melvin, Matthew W. Salzer, Alexander V. Shashkin, Claudia Timmreck, Eugene A. Vaganov & Rob J. S. Wilson. Tree rings and volcanic cooling. Nature Geoscience 5, 836–837 (2012) doi:10.1038/ngeo1645
2014 [Rutherford, Scott and Michael Mann. Missing tree rings and the AD 774–775 radiocarbon event](http://www.nature.com/nclimate/journal/v4/n8/full/nclimate2315.html?WT.ec_id=NCLIMATE–201408]. Nature Climate Change. Vol 4, August 2014.
I’m reading Disaster!: A History of Earthquakes, Floods, Plagues, and Other Catastrophes by John Withington, who also wrote about other disastrous things such as disasters specific to London. It is a couple of years old (and thus does not include the recent Japan earthquake and tsunami). This is more of a reference book than a sit-down-and-read-it book, and it lacks detailed presentation or critical analysis of sources, but if you want to know about a particular past major disaster or category of major disasters (volcanoes, floods, tsunamis, etc.) this is a good starting point. Reading just through the famous volcano disasters, for instance, one can get a good feel for the relationship between people’s experiences with volcanoes and an understanding of how these events play out and create the havoc they are responsible for. For example, recent research on the cause of death of Romans at Pombeii during the Plinean eruption of Vesuvius suggested that most of the victims found entombed in hardened volcanic effluence died by being cooked instantly as though tossed into an ultra-hot oven all at once. Reading in Withingon’s book about eye witness accounts several similar volcanoes (including Vesuvius), one would not be surprised about this at all. In Martinique, Mount Pelée totally destroyed the thriving cosmopolitan town of St. Pierre in 1902. Eye witness accounts attest to people watching the eruption from a nearby ship suddenly bursting into flames, with some individuals sizzling as they hit the surface of the sea into which they leapt to save themselves (unsuccessfully).
Another interesting theme that runs through the book is the relationship between leadership, or lack thereof, and the level of magnitude of the disaster’s impact on people, which reminds us of the difference between Katrina and Sandy. In the case of Mount Pelée, local officials had an interest in keeping everyone in town for an upcoming election, so the leadership assembled a commission of sycophants to “study” the volcano’s unrest and determine that it would not threaten the town. Almost every person who lived there was killed when the main eruption occurred, with the death toll being in the tens of thousands. Another theme is the vital importance of effective monitoring and planning for volcanoes, floods, earthquakes, and tsunamis.
This is a book without pictures so the Kindle edition is a good choice if you like eBooks. Also, note that the British edition has a slightly different title.
There are thirteen canary islands. But there are about to be fourteen. Well, actually, there’s probably more than 13 as these island chains usually have a few extra rocks sticking up that people aren’t sure about including in the final count. The point is, there is a volcano erupting under the sea in the Canary Island chain and the top of the volcano is about 70 meters from the surface of the sea according to some reports.
Not long after Yellowstone Park was officially created, a small group of campers were killed by Nez Perce Indians on the run from US troops1. More recently, the last time I was in the area, a ranger was killed by a Grizzly Bear (so was his horse) on the edge of the park. A quick glance at my sister’s newspaper archives (Lightning Fingers Liz a.k.a. Caldera Girl has been running newspapers in the region for nearly forty years) shows a distinctive pattern of danger in the Caldera, mainly in relation to the lack of turning lanes on highways with poor visibility and other traffic related hazards.
So, no, the Yellowstone Caldera is not especially safe, what with cars, humans, and griz everywhere. Oh, and every now and then somebody falls into a geyser. But you are probably here because you are interested in a different question: Is the Yellowstone Caldera, the volcanic feature, not the natural and cultural landscape, dangerous? In other words, is one of the largest volcanoes to exist on the earth ever gonna blow? Like this?
Even at the most extreme edges of the flow of stuff out of the volcano Pompeii, at the far edge of the mud and ash that came from the volcano’s explosion, the heat was sufficient to instantly kill everyone, even those inside their homes.
Whitney Houston took a car ferry from Britain to Ireland to attend her concert, rather than flying. Barack Obama has canceled his trip to a state funeral in Poland. A very large magical snake protects a canyon in south Africa. These things are connected a lot more closely than you might think.
I had mentioned earlier that the volcanoes of the Virugna region in the Western Rift Valley (as well as other highland spots) have often been islands of rain forest separated from each other by different habitats, including grasslands and wooded savannas. this has produced an island effect that has been a laboratory for evolution, and it is likely that these forest islands (and others in the greater region of east Central Africa and western East Africa) have been the loci of evolution of many endemic species. (See Island Africa: The Evolution of Africa’s Rare Animals and Plants by Kingdon for an excellent overview of the Island Effect in highland regions of Central and East Africa.)
It is probably not a coincidence that two of the three subspecies of gorilla live within sight of each other (and of the main subspecies, the lowland gorilla) within this region. The Virunga volcanoes are not old enough to have supported island forests for the evolution of these specific subspecies, but other highlands in the region, or other volcanoes (perhaps in the Eastern Rift) may well have been the location in which they evolved.
And, as it turns out, there is reason to believe that the split between chimps and humans occurred on one of these volcanic mountain tops several million years ago. Or, at least, in an environment geologically similar to the upper reaches of the Virunga Volcanoes. But to tell this story right, I have to go back a few years. Continue reading Nyamulagira Volcano and Human Evolution→
Nyamuragira, just now erupting, is one of the numerous Virunga Volcanoes, which form a large cluster of volcanoes spanning the border of Congo, Rwanda and Uganda, between Lake Ex-Edward (a.k.a. Lake Rutenzege) and Lake Kivu. The largest population center is Goma, on Lake Kivu, along the southern margin of the lava fields from these volcanoes, and made famous in recent years as the site of numerous excursions of warfare, refugee movements, and volcanic lava flows. I’ve written about Goma and a little about the Volcanoes in the Congo Memoirs.
Mount Rainier (14,410 ft) has lately attracted a small amount of attention because of what is considered by some an increase in seismic activity there, so I thought it might be nice to get a baseline description of this volcano for those of you interested in such things. For scientifically accurate information and interesting discussion on the mountain, keep an eye on Eruptions Blog.
As you have surely heard, the Yellowstone Caldera … the place where Old Faithful and the Geyser Basin reside … has been undergoing increased “activity” including some earthquakes and a rising up of the land. Is this a big problem? Should the evacuate? Should those of us living only a few states away start wearing earplugs? Continue reading The Yellowstone Problem→