Here it is, the answers to your volcanic questions for Dr. Clive Oppenheimer. His new book, Eruptions that Shook the World, comes out this week and I'll have a review as soon as I get back from my West Coast lab/fieldwork extravaganza.
He did a great job answering many of your questions, so a big thank you to Dr. Oppenheimer for taking the time to answer so thoughtfully. Enjoy!
Dr. Clive Oppenheimer (or, possibly, a Time Lord).
Firstly, I have to say – what an amazing set of questions… Thanks, everyone, and thanks Erik for setting this up! I’ll do my best but I’m out of my depth on some of these! I’m also wondering which ones have been posted my sneaky grad students, trying to catch me out!!
Not yet! The 1258 event is identified from fallout in polar ice cores. Richard Stothers at NASA Goddard associated its climate effects with a contemporary outbreak of the bizarre cult of self-flagellation in Europe! One of the more recent suggestions for the responsible volcano is Quilotoa in Ecuador, based on radiocarbon dating of charcoal in a thick pumice deposit. But radiocarbon dates allow a lot of wriggle room and Quilotoa’s eruption doesn’t look big enough to account for the amount of sulfur in the ice cores. Another suggestion is that there were two more or less coincident eruptions, one each in northern and southern hemispheres. So, the case remains open.
When lava cools down, it picks up so-called “thermal remanant magnetization”. In essence, the iron-rich mineral minerals (such as magnetite) in the molten rock line up with the prevailing magnetic field of the Earth like compass needles. This turns out to have important applications in dating rocks and reconstructing the shifts of the continents over geological time.
Magma chambers still lie beneath many geothermal regions. In 2009, an exploration project in Iceland even managed to drill into magma! But there are also “hot dry rock” geothermal projects where the heat comes from radioactivity rather than a magma source. Active volcanoes aren’t necessarily ideal sites for geothermal exploitation – the infrastructure is vulnerable in the event of future eruptions, but also the hot fluids circulating beneath the volcano can be very acidic. Before its massive 1991 eruption, there had been geothermal exploration at Mount Pinatubo in the Philippines but the hot fluids circulating beneath the volcano were found to be too corrosive to exploit.
Geysers are generally found in volcanic regions and ultimately the heat will often derive from deeper magma bodies.
No. Anthropogenic emissions of CO2 today are about 35 gigatons a year – roughly 100 to 200 times what comes out of volcanoes. There was a good paper on this topic written by Terry Gerlach, a leading authority on volcanic gases, published by the American Geophysical Union in June.
(Note from Erik: You might also remember the discussion we had on the Gerlach paper earlier this summer.)
Do you fear that the large amounts of SO2 seen lately and a rise on volcanic activity may lead us to a new Ice Age?
I’m unaware of evidence for a rise in volcanic activity. I can see that why it might appear eruptions are on the increase but this is a reflection of our era of instant news reporting around the world – an eruption happens in Chile and its being tweeted about in real time. Twenty years ago, it probably wouldn’t have made the international news. Also, we are more exposed to volcanic activity globally. Just in my lifetime the global population has doubled. And we’ve been sensitized to hazards like aviation and ash clouds. While volcanic SO2 emissions in large doses cool global climate, as they did after the 1991 Pinatubo eruption, the effects only last a few years. There have been some efforts to run climate models for ‘super-eruptions’ with massive SO2 release and even these fail to start an ice age. Interestingly, artificial release of SO2 into the stratosphere is one of the proposals put forward to combat global warming – so called “stratospheric geoengineering” or “solar radiation management”. The basic idea would be the equivalent of a Pinatubo going off every 4 years. There’s a good debate on whether or not this is a good idea here.
What can people do if a super-volcano comes up?
I tried to think this through for the final chapter of “Eruptions that shook the world”. It’s such a remote possibility that I think at this stage what is needed is to look at the probabilities and potential scale of impacts, and then look at whether it is worth doing something about such a low-probability but high consequence scenario. If one did happen, there are two key areas to think about. First, the region around the volcano where the effects of ash will be greatest – a radius of 500 miles, say, and the associated problems of search and rescue, etc. Second, the worldwide food security issues arising from the likely global climate change due to a very large release of sulfur to the atmosphere.
I like them best when they are run by a volcanologist… ;-)
It has been suggested based on evidence from seismic imaging that the two volcanoes share a single magma source at a depth of more than 5 miles in the crust. But they erupt rather different compositions of magma, which is harder to reconcile with a single source.
In the first billion or so years of Earth’s history it is likely that volcanism was different on Earth because of higher temperatures in the Earth’s mantle. As you say, it’s lost a good deal of heat since then despite the ongoing heat production by radioactive decay. But this is a VERY gradual process, and over the timescales of, say, the last millions of years, there isn’t any evidence of things slowing down. If anything there has been quite a cluster of “super-eruptions” in the past 10 million years or so (e.g., see the paper by Mason et al.). The conclusion of this is that there is a roughly 1% chance of a super-eruption (magnitude 8 and above) in the next 500 to 7000 years or so (the wide margin of uncertainty highlights our lack of knowledge of these huge events).
Great earthquakes (around magnitude 9) do seem to trigger volcanic eruptions but how they do it is not well understood. For instance, Talang volcano in Sumatra erupted a few months after the 2004 Sumatra-Andaman earthquake. Thomas Walter and Falk Amelung showed statistically that within a range of 1000 km or so of the epicenter, there are more eruptions in the 3 years after a great earthquake than in the 50 years before. They argued that the cause might be stresses set up by the earthquake rupture that act to decompress a magma chamber. But in truth we’re still rather in the dark as to the mechanisms.
Some of the recent notable eruptions (Pinatubo, 1991; Chaiten, 2008; Nabro, 2011) were the first in recorded history for the volcano. While there is some evidence that even large eruptions can involve magma only recently intruded into the crust, generally speaking, bigger events happen at volcanoes that have been long dormant, during which time magma was accumulating in the chamber. Super-eruptions presumably need an even longer time to accumulate such huge volumes of magma. The known super-eruption hotspots of the past 10 or 20 million years do include familiar sites: Yellowstone, Toba, Taupo, Long Valley (California) and the central Andean calderas of Chile/Bolivia/Argentina. But the next one could be somewhere else like the African Rift Valley, where there are numerous caldera systems that are less than a few million years old.
See answer to Ugrandite below.
Given all the things that could be funded, I think we do reasonably well in volcanology. Certainly events such as the Eyjafjallajökull eruption in 2010 or Mt St Helens in 1980, help to spur on the science, not only because they offer new observations and stimulate new ideas, but also because they attract funding. But I do think sometimes it would be nice to be able to get some funding for more wacky ideas that the agencies will think too risky. Most of all though, I wish there was less bureaucracy in applying for funds and project reporting. You can spend months with a dozen or more colleagues putting together a proposal that has only a 5% chance of success. And reporting on some grants is unbelievably demanding – requiring huge internal documents that will likely never be read by anyone. This detracts from getting any results in the first place. And it surely hampers writing up the findings for scientific peer review and for wider public dissemination. While thinking hard about what you really want to achieve scientifically is a good thing, wasting huge amounts of time that you could be actually doing the work is very frustrating and it puts a lot of people off applying for funds in the first place. This whole process needs a much lighter touch in my opinion. Rant over.
It all depends how much accuracy is “some” accuracy! The basic problem of course is that except for a few drilling projects that have cored into active magma, just about everything we know about present-day magma systems is obtained indirectly – from measuring gas emissions, ground movements, earthquakes; from techniques such as seismic tomography; and of course from good old petrology. But all these lead to the old problem of imagining what the dragon looks like based just on seeing its tracks! Still, I do think volcanology is improving to the point where evidence from different techniques points to coherent conclusions and that gives confidence in the interpretation of what is going on below the ground.
Wow – that’s a tough one – I have so many great memories of working on volcanoes! Up there with the most memorable moments would have to be my first field season on Erebus volcano in Antarctica. The weather was bad when we reached field camp and the first visit to the crater rim was in cloud. I could hear something fizzing away deep in the crater but I certainly couldn’t see anything. But it was very atmospheric and exciting. It was perhaps a week before the weather cleared, and this period of anticipation made the reality all the more sensational. The views from 12,000 feet up in Antarctica are spectacular enough but having a lava lake and ice caves up there transports you to another world altogether. Another very memorable spell of fieldwork was on Oldoinyo Lengai in Tanzania. Firstly, you feel like you are looking off the top of the Eifel Tower from the crater rim – it is extraordinarily steep! Second, there’s nothing more bizarre than the sight of a volcano erupting washing soda!As for proudest moments, two aspects of the work come to mind. First are the surprises that pure research throws up from time to time. I’ve been working on Erebus with the US Antarctic Program for eight years now and research teams have been going there for forty. But no one had noticed that the volcano’s lava lake “breathes” with a ten minute cycle. The result fell out from an analysis of hundreds of thousands of spectroscopic measurements of gas emissions from the lava lake, which showed a more or less periodic change in composition. I couldn’t believe it at first and thought there had to be some mundane artifact of the data processing. When the same time cycle showed up in analysis of a completely independent dataset of thermal images I was certain, and it’s given us tremendous insights into how the shallow part of the volcano’s plumbing system works. The second rewarding aspect of the job probably sounds corny but it’s true: teaching. Recently, a student I had taught ten years ago contacted me out of the blue to say how much he’d valued his experience working on Teide volcano for his undergraduate thesis. Knowing that from time to time you can help to inspire people is very humbling. Sorry – that was supposed to be a one-line answer, wasn’t it!?
A great and tough question: I’m just going to say the first five things that come into my head: the spectrograph, the volcano observatory, the seismometer, internally-heated pressure vessels, and space rockets. I suppose these are all a means to the knowledge we have of volcanoes. But many breakthroughs have come about thanks to meticulous observations of volcanoes and of particular eruptions. We owe an awful lot to pioneers of volcanology like Macedonio Melloni (first director of the Vesuvius observatory), Thomas Jaggar, Frank Perret and Alfred Lacroix, and all the people in volcano observatories around the world today.
It’s true that Erebus phonolite is more viscous (up to a hundred times more, perhaps) than your typical basalt at Erta ‘Ale or Kīlauea, also known for lava lake behavior. But it definitely has a lava lake! On the other hand, Erta ‘Ale, Kīlauea and Nyiragongo are not known for Strombolian eruptions, while they often burst through the lava lake of Erebus. Again, this may have something to do with Erebus magma being that much more viscous. A factor that complicates our understanding of the viscosity is that the lava in the lake is very frothy and the effect of bubbles is hard to calculate. It’s definitely something we need to understand better and I’ve been racking my brains to think how we could make direct measurements in the lava lake without having to rappel into the crater!
Large eruptions do change atmospheric composition especially due to the sulfurous dust they generate in the stratosphere. It’s these small particles that reflect some sunlight away from reaching the Earth’s surface, which causes an overall cooling effect on climate. The 1991 eruption of Pinatubo taught us most of what we know about this process. As it was twenty years since the eruption last month, I wrote a short piece on it here.
The ash and sulfur from powerful explosive eruptions at low latitudes can reach the whole globe, in principle, depending on how the atmospheric circulation is working at the time. How far the direct effects of fallout can be harmful to ecosystems on the ground depends on factors like the amount of fluorine carried on the ash, and of course the thickness of ash that accumulates, but it could easily be across a zone hundreds of miles from the volcano for a modest event. On the other hand, very light dustings of ash can actually be beneficial for agriculture since they can supply nutrients such as selenium to the soil.
For sure, landslides into the sea can generate tsunami. And large chunks of volcanic islands break off or slump during their geological evolution. But modeling the tsunami waves and coastal run-ups from extreme case scenarios, which are extremely rare of course, is very difficult. In principle, the idea that damaging tsunami could occur in the Atlantic due to mega-landslides of Cumbre Vieja, cannot be ruled out. Here’s an interesting paper on “a general example of what might be expected from an extreme slide event”.
Yes – I think so. The Laki eruption of 1783 (also in Iceland) is often cited as one of the closest parallels we have to a flood basalt. It erupted an estimated 14.7 cubic kilometres (about 3.5 cubic miles) of lava in 8 months. Much of the lava was erupted in bursts at estimated peak rates of over 6000 cubic metres per second. That’s about 1500 times the average rate on Kīlauea over the past 30 years! If we just take the 14.7 cubic kilometres in 8 months, and imagine the eruption going on for a million years (about the time it took to form the Columbia River basalts) at the same rate, that adds up to more than 20 million cubic kilometres of lava. You’ve already got 100 times more lava than you need to match the Columbia River basalts. However, at Laki, the lava flows reached only 40 km, while individual flows in the Columbia River basalt travelled 300 km! So, while some of the eruptive processes are surely qualitatively parallel (e.g., structure of pāhoehoe flow fields), we can only extrapolate so far from what we have seen of modern basaltic volcanism to imagine what the flood basalts must have been like.
I’m still puzzled by monogenetic volcanic fields such as Auckland or, to a lesser extent, the Eifel that are not located in spreading zones. These fields are generally characterized by small volume monogenetic basalt cones erupted through a pretty thick layer of fairly stable continental crust. How does such a small volume of basalt manage to makes its way through so much crust, particularly when the field is not in an active seismic zone like at Auckland?
Monogenetic volcanic fields certainly through up some puzzles to understand their spatial and temporal characteristics, and their present day hazards. Something else that also puzzles me is the evidence for very rapid magma ascent rates you find in places like San Carlos in Arizona and Lanzarote where basalt eruptions have transported dense chunks of plutonic rocks to the surface. I guess that question of speed might have something to do with small volumes of melt making it all the way to the surface.But as you say, extensional stress regimes also seem to have something to do with it in the case of monogenetic fields. One idea, in the case of the Auckland field, seems to be a structurally-weakened crust allowing rapid magma ascent. I’ve also read there is evidence for a prevailing extensional regime in the region. The picture in the Eifel seems even more complex – I think there are supposed to have been alternating phases of extension (e.g., the nearby Rhine Graben), compression and uplift, and evidence associating the volcanism to a small hotspot.
I’ve been thinking about oscillating magma levels a lot (doesn’t everyone?), since working on Erebus. There it is very clear that the magma level rises and falls every 10–20 minutes, perfectly in time with changes in the speed of the lava at the surface, and changes in the gas composition. In this case I think it has a lot to do with the dynamics of magma flow in the top part of the feeding conduit, and also the fact that there is a counterflow of ascending and descending magma, which can develop instabilities. This doesn’t explain all the examples you give but I do think a lot of this kind of behavior comes down to rather shallow processes because it is not so far below the surface that magma changes hugely in its properties as water fizzes out of the melt; bubbles expand, coalesce and change magma permeability; microlites grow like crazy, etc. These processes are likely I think to induce all kinds of feedback loops.
Mike Rampino was one of the first to propose antipodal focusing of seismic energy from massive bolide impacts as a trigger for giant basaltic eruptions. The distribution of hotspots (mantle plumes) worldwide also seems to show they come in antipodal pairs. There hasn’t been much work on the idea, though one idea is that they are related to bolide impacts with magmas erupted at both the impact site and due to seismic focusing at the opposite end of the Earth. It is not a widely accepted idea, though. Jury out but working harder on another case?
Sorry – I haven’t come across that term before. The ignimbrites of the Sierra Madre Occidental in Mexico are among the largest deposits of silicic volcanism worldwide, erupted roughly 30-million-years ago. There’s an interesting idea that their eruption led to a severe global climate cooling event via iron fertilization of the ocean (from associated ash fallout).
Hmm – tough question… If Earth takes a hit from a large meteorite that could influence the odds… Just possibly, de-icing the whole planet through global warming – at least that is likely to increase statistically the rate of volcanism in areas where volcanoes are presently under ice. In reality the odds of a super-eruption are so poorly known that the thing that will influence them most is making some better, more reasoned estimates! The “1-in-500” figure is certainly a crude guesstimate. To improve on it would need more comprehensive and more accurate data on eruption ages and deposit volumes for the past millions of years, and a more rigorous set of calculations, probably based on some kind of extreme value statistics.
See comment on Renato's second question (see above).
Nabro offers another example of how a volcano we have never heard of can rewaken and produce its first eruption in recorded history. Yes – I have been inside the caldera though not quite in the intended circumstances. I’d been carrying out fieldwork on nearby Dubbi volcano with Eritrean colleagues and a PhD student Pierre Wiart. On my last day in the field, I hiked up Nabro. I walked straight into a military camp and let’s just say that they were as surprised to see me as I was to see them... This was shortly before Eritrea and Ethiopia went to war and the volcano is right on the border. They escorted me off the mountain as the sun set and all I could do was look in frustration at the young pumice deposits and obsidian flows out of the jeep window. I am hoping to return with a small team soon to survey the effects and products of the recent eruption. We don’t know yet what the lava/pumice compositions are but, as you say, much of the edifice is made of trachyte. If it is a trachyte eruption that is pretty rare, historically speaking. We have no dates for the past eruptions but that is something I would like to work on in future. The ignimbrites look impressive in satellite images – geomorphologically, they remind me a lot of the ignimbrites in the central Andes.
Ah! Roiling cloud and thunder would make me the grandson of J. Robert Oppenheimer perhaps… The truth is that portrait photography is all about lighting, a grubby lens, and a decent range from the subject.
We’ve come a long way over the last decades in terms of our understanding of volcanic processes. But when you look at how many papers there are on volcanoes like Kīlauea and Etna, and how they still keep coming out, you soon realize there really isn’t that much we are sure about*. It’s humbling, too, to read papers from Jaggar, Perret, Lacroix et al., who were already thinking hard about the same problems we are still looking at a century later. I think the future of volcanology is very bright though – there is so much research going on around the world and looking at so many angles, from magma rheology to risk assessment. And technological developments will always bring new insights to the subject. At the monitoring end, I think that laser spectroscopy and lidar systems will provide the next generation of tools for gas measurements, including the potential for routine monitoring of isotopic compositions of gas emissions and remote measurements of CO2 emission rates. Because volcanoes are potentially so hazardous and difficult to access, remote sensing methods will continue to be at the fore, especially from satellites, but increasingly I think we will see robotics and UAVs contributing to volcanology.In the laboratory, micro- and nano-scale analytical techniques such as x-ray and neutron microtomgraphy are coming of age and will provide unprecedented detail on the nature and behavior of bubbly magmas. Experimental techniques on natural and synthetic samples will bridge the gap between surface observations and microanalytical techniques, and will lead to improved physical and chemical models for magma storage, transport, degassing and eruption. Finally, deep drilling projects are expensive but they do give us tremendous windows into what is really going on down there.*I just did a very unscientific survey – number of papers with different volcano names in the title. Etna won (with 1323 papers) followed by Mt. St. Helens (1056). Vesuvius came third (845). Erebus only got 114 – must do something about that…
Following on from Ugrandite's question (see above). I’d like an integrated laser spectrometer (for gas molecular and isotopic composition) and lidar system (for CO2 fluxes) that will comply with airline carry-on bag allowances. I’d like it to be small so I can easily travel with it. But mainly I think that once we get into isotope measurements of volcanic gases in the field (rather than collecting samples and taking them back to the lab), it is going to revolutionize volcano geochemistry. I also think the prospect of making reliable, remote-sensing measurements of CO2 flux from volcanoes will be a tremendous advance – it will get round a lot of drawbacks of the current reliance on SO2 measurement. Do you know where I can get one?
I got the idea in the mid-90s. Around that time there was a revolution underway in the application of genetics to understanding human origins and migrations (“Mitochondrial Eve” and all that). This got me interested in how volcanism might have shaped human behavior and development through prehistory and history. I wondered how different the world would be today if all the volcanoes had been switched off a million or a hundred thousand years ago. I was also strongly influenced by the meticulous work of archaeologists such as Payson Sheets, Robin Torrence and Patricia Plunkett who were finding “Pompeiis” around the world, and generating new hypotheses concerning the intersections between culture, human ecology and volcanism. I wanted then to synthesize from all this something new concerning the interrelationships between humans and volcanoes, and to think about the lessons that might help us prepare for future volcanic events of a scale not seen in modern times.
It’s a really interesting point and worthy of research I think. I don’t know the answer and it is difficult to know if what we have seen lately is volcanology’s “fifteen minutes of fame” or something that will leave a more lasting memory. I wonder if the emphasis on aviation hazard is giving a distorted view of volcanic risk, though.
Somewhat by chance. Before going to University I read the original Pelican edition of “Volcanoes” by Peter Francis (it is still a great introduction to the science and you can find used copies for a few cents online!). I’d scribbled all over it while travelling in Indonesia during a “gap year” after high school, noting features I was recognizing in the country’s tremendous volcanic landscapes. At university it was seismology that really captured my interest. One of my first jobs was working as a seismogram analyst in Wellington, New Zealand. But when I was applying for PhDs, there was a project at the Open University in the UK that caught my attention. The short description implied there would be a lot of fieldwork combined with satellite remote sensing. The prospect of working on active volcanoes appealed greatly of course, and the connection between field and spaceborne observations piqued my curiosity. The project was supervised by Peter Francis himself, along with Dave Rothery. I was offered another project on seismotectonics (also working in Chile) and agonized over which one to do. It was the remote sensing aspect that tipped the balance in the end – it seemed the next best thing to going into space and the field was expanding hugely at that time. I have never regretted my choice – it was definitely one of those key turning points one gets in life.
The great thing about volcanology is that just about anyone can get involved: including physicists, engineers, geographers, mathematicians, programmers, climate scientists, anthropologists, archaeologists, ecologists, civil protection managers, art historians, actuaries.... Volcanology thrives on this diversity – I don’t think we would understand nearly as much about volcanoes and their impacts if the subject was only studied by geologists. The most important thing I think is to have an enquiring mind and plenty of curiosity – that way you keep asking questions. Two quite general “talents” have helped me in volcanology and science more generally. I’m quite observant, which is handy for someone whose research is based strongly on observations! I also enjoy writing even if I find it a struggle sometimes. Written communication is still the gold standard of most science and approaching that with enthusiasm rather than dread is a great help, I think.
An easy question at last! It would have to be Peter Francis, who was my PhD advisor. Peter did not fit the mold – he went to university in London in the swinging sixties but his passion was Mozart, not the Stones. He challenged just about anything I said or wrote – we could argue for an hour as to whether a condiment on a restaurant table was capsicum or oregano! He wrote of the first draft of my PhD thesis that reading it was like eating marshmallows (i.e., he felt sick after the first couple of chapters!). His combative and Socratic approach taught me about doing science, while the freedom I had as a student at the Open University, combined with the line-up of volcanological expertise on the Faculty, enabled me to explore and indulge a growing fascination for volcanoes.
Top left: The main summit crater at Erebus in Antarctica, one of Dr. Oppenheimer's many field sites.