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How much methane came out of that hole in Siberia?

Filed under: — david @ 13 August 2014

Siberia has explosion holes in it that smell like methane, and there are newly found bubbles of methane in the Arctic Ocean. As a result, journalists are contacting me assuming that the Arctic Methane Apocalypse has begun. However, as a climate scientist I remain much more concerned about the fossil fuel industry than I am about Arctic methane. Short answer: It would take about 20,000,000 such eruptions within a few years to generate the standard Arctic Methane Apocalypse that people have been talking about. Here’s where that statement comes from:

How much methane emission is “a lot”? The yardstick here comes from Natalie Shakhova, an Arctic methane oceanographer and modeler at the University of Fairbanks. She proposed that 50 Gton of methane (a gigaton is 1015 grams) might erupt from the Arctic on a short time scale Shakhova (2010). Let’s call this a “Shakhova” event. There would be significant short-term climate disruption from a Shakhova event, with economic consequences explored by Whiteman et al Whiteman et al (2013). The radiative forcing right after the release would be similar to that from fossil fuel CO2 by the end of the century, but subsiding quickly rather than continuing to grow as business-as-usual CO2 does.

I and others have been skeptical of the possibility that so much methane could escape from the Arctic so quickly, given the century to millennial time scale of warming the permafrost and ocean sediments, and point out that if the carbon is released slowly, the climate impacts will be small. But now that explosion holes are being found in Siberia, the question is

How much methane came out of that hole in Siberia? The hole is about 80 meters in diameter and 60-100 meters deep.

It’s hard to say exactly how much methane did this, because perhaps the crater allowed methane to be released from the surrounding soil. There may be emissions in the future from permafrost melting laterally from the sides of the hole. But for a start let’s assume that the volume of the hole is the same as the volume of the original, now escaped, bubble. Gases are compressible, so we need to know what its pressure was. The deeper in the Earth it was, the higher the pressure, but if we are concerned about gas whose release might be triggered by climate warming, we should look for pockets that come close to the surface. Deep pockets might take thousands of years for surface warming to reach. The mass of a solid cap ten meters thick would increase the pressure underneath it to about four atmospheres, plus there may have been some overpressure. Let’s assume a pressure of ten atmospheres (enough to hold up the atmosphere plus about 30 meters of rock).

If the bubble was pure methane, it would have contained about … wait for it … 0.000003 Gtons of methane. In other words, building a Shakhova event from these explosions would take approximately 20,000,000 explosions, all within a few years, or else the climate impact of the methane would be muted by the lifetime effect.

What about the bubbles of methane they just found in the Arctic ocean? There were reports this summer of a new expedition to the Siberian margin, documenting vast plumes of methane bubbles rising from sediments ~500 meters water depth.

It is certainly believable that warming ocean waters could trigger an increase in methane emissions to the atmosphere, and that the time scale for changing ocean temperatures can be fast due to circulation changes (we are seeing the same thing in the Antarctic). But the time scale for heat to diffuse into the sediment, where methane hydrate can be found, should be slow, like that for permafrost on land or slower. More importantly, the atmospheric methane flux from the Arctic Ocean is really small (extrapolating estimates from Kort et al 2012), even compared with emissions from the Arctic land surface, which is itself only a few percent of global emissions (dominated by human sources and tropical wetlands).

In conclusion, despite recent explosions suggesting the contrary, I still feel that the future of Earth’s climate in this century and beyond will be determined mostly by the fossil fuel industry, and not by Arctic methane. We should keep our eyes on the ball.


  1. N.E. Shakhova, V.A. Alekseev, and I.P. Semiletov, "Predicted methane emission on the East Siberian shelf", Doklady Earth Sciences, vol. 430, pp. 190-193, 2010.
  2. G. Whiteman, C. Hope, and P. Wadhams, "Vast costs of Arctic change", Nature, vol. 499, pp. 401-403, 2013.
  3. E.A. Kort, S.C. Wofsy, B.C. Daube, M. Diao, J.W. Elkins, R.S. Gao, E.J. Hintsa, D.F. Hurst, R. Jimenez, F.L. Moore, J.R. Spackman, and M.A. Zondlo, "Atmospheric observations of Arctic Ocean methane emissions up to 82° north", Nature Geoscience, vol. 5, pp. 318-321, 2012.

106 Responses to “How much methane came out of that hole in Siberia?”

  1. 1
    Hank Roberts says:

    David, much appreciate the sanity check.

    Could you or one of your grad students :-) make any guesstimate about my “undergravel filter” scenario — speculating wildly that oil and gas exploration may have left unfilled boreholes intersecting permeable strata, so warm water could move down, across, and back up along with bubbles where the structure happened to favor that?

    I have no guess at numbers on drill test holes intersecting hydrates. I know there’s a history of oil and gas exploration and a new push to tap the same areas currently in progress. The cost and effort to properly fill with concrete and cap an exploratory hole rather than leaving the steel to rust out might well be avoided if nobody imagines a problem could happen.

    Same question really for these land holes — are they in areas where drilling was done? And are they deep enough to encourage circulation, transporting heat faster than diffusion does?

    I’m just looking at the assumption of solid strata and diffusion and wondering, could we screw that up and produce a geological situation unlike that in paleo times, when diffusion was limiting the rate?

    Presumably some competent climate scientists working for the petroleum industries would have more facts on what’s there.

    As Ray Bradbury said, I don’t write to predict the future — I write to prevent it.

    [Response: As a modeler of the deep sediment column, I go to talks about observations of the real world (geology, in other words), and am struck by how simplistic the models are. It’s like clouds in the atmosphere, extremely complex, represented only in some bulk way in the climate models. The real sediment column has faults and explosions (there are lots of things in the ocean that look like this thing in Siberia, they are called “pockmarks”). My hunch for what it’s worth is that drilling holes are probably not a huge addition to the complexity of the real heat transport of the sediment column. The issue comes up also when considering sequestering CO2 in the ground. David]

  2. 2
    Eduardo Vargas says:

    Thanks a lot David. Seeing another post on methane, I encountered with the fact that the oceans would degas at one point some of the CO2 that we emitted since the Industrial Revolution. I also then found a comment by Gavin which said that the degassing of the oceans would not happen any time soon, and that we where at most a century away. The question is, how much of the CO2 the ocean absorbed would be released back?

    [Response: Ultimately, the CO2 inventories of both the atmosphere and the ocean are regulated by the CO2 weathering thermostat mechanism, on a time scale of hundreds of thousands of years. By the time that thermostat has equilibrated, if nothing else were changing, all of the fossil fuel CO2 that the oceans took up, they would give back. On a more human time scale, Gavin is right that the atmosphere is so over-loaded with CO2 right now relative to the ocean that it would take a lot of removal from the atmosphere before that could be reversed. David]

  3. 3
    Tony Weddle says:

    Thanks for putting things in perspective, David. However, although 20,000,000, in a short time (years?) sounds a lot, I hope you’re not using the incredulity argument (“it’s a lot and so couldn’t happen”). If this did come of pockets of free methane trapped in shallow permafrost, is there any way to estimate how many such pockets there may be ready to burst forth? Could it be 20,000,000? I suspect that we simply don’t know.

  4. 4

    “…the future of Earth’s climate in this century and beyond will be determined mostly by the fossil fuel industry, and not by Arctic methane.”

    One certainly hopes so, since we have no direct control over Arctic methane releases.

    Although the quantitative assessment presented is somewhat reassuring, the main takeaway is perhaps not the scale, but the fact that we’re seeing something new (or that we presume to be new, at least.) It’s a climate impact and a climate feedback (albeit one that’s quantitatively marginal at present.) If we ‘take our eyes off the [fossil fuel] ball’, we’ll see much more of such phenomena.

    (Well, I’m guessing we’ll see more of them regardless, but perhaps emissions mitigation will allow us to keep them within the radiatively marginal category.)

  5. 5
    jemima says:

    Of course there’s methane in and around a hole melted through permafrost in a gas producing region. Explosions don’t make smooth-bored holes like that but collapsed pingos do, possibly with gas-pressure driven ejection of material upon melting of the pingo ice cap. Seriously – has there ever been an “explosion” of something that left a smooth-bored hole in the ground like that?

  6. 6
    Tim Osborn says:

    Just trying to imagine what 20 million explosions/holes would look like.

    Area of permafrost is a bit less than 20 million km^2. So 20 million such explosions/holes is a bit more than one for every km^2 of permafrost.

    With a diameter of 80 m, one hole for every km^2 of permafrost is about half a percent of the area.

    One every km^2 seems a lot within a few years. What about one every 30 km^2 spread over a 30-year period? Is that more “feasible”? With a lifetime of ~10 years, spreading emissions over 30-year period would of course reduce the peak atmospheric burden (though CH4 lifetime would presumably increase with higher CH4 concentration).

  7. 7
    mikeworst says:

    You refer to a methane explosion but close-up pictures of the pit clearly show polishing and erosion by ice. This is a collapsed Pingo and nothing more.

  8. 8
    Arun says:

    Since the Russian area of permafrost is more than 10 million square kilometers (e.g., ) we need less than 2 methane explosions per square kilometer in a few years.

  9. 9
  10. 10
    wili says:

    Thanks for this perspective. Just in case people think David is exagerating in claiming that people are talking about a “Arctic Methane Apocalypse,” I provide for your enjoyment links to recent discussions of these topics by two of our favorites, Guy McPherson and AMEG/ArcticNews: (Though I do think the first schematic here could be useful as a basis for further discussion.)

    I would like to ask David, though: In the past, you have said that there is no pathway for clathrates to escape from their deep repositories. Could these holes represent such possible pathways? Could they happen on the seabed?

    [Response: I didn’t mean to say that, but I might have meant to say that the time scale for heat getting down to where the hydrates are is long (slow). Actually it’s clear that methane gets through the “hydrate stability zone” in surface sediments, which ought, thermodynamically, to act as cold traps and catch it. Some might be due to high-salinity channels that form (hydrate formation leaves behind salt), or upward migration of heat. There are tons of “explosion marks” on the sea floor, called “pockmarks”, and they are often correlated with “wipeout zones” in seismic images, in which the sedimentary layers are smoothed out by some disturbance. ]

    Also, if you could weigh in on whether you think these things are collapsed pingos (which seems to be the WUWT position–reason enough to doubt it, imho) and why, it could be useful in my (mostly fruitless) efforts at beating back denialists on other blogs. Thanks again.

    [Response: I’m not a specialist but that seems to be the consensus. David]

  11. 11
    prokaryotes says:

    Extrapolating based on isolated incidents, indeed offers a calm picture of the Arctic circle deglaciation. However, in the big picture i think there are a lot of unknowns involved which need to be better identified. Such as wildfire feedback, coastal erosion, weather/atmospheric anomalies, seasonal changes, species adaptation, ocean currents etc.

    What exactly can we expect in the future, will thaw progress gradual or exponentially, based on feedbacks? This isn’t addressed enough. There should be more communication about possible future scenarios, in particular to support decision making. On the bottom line, we need to reduce CO2 to reduce future risks (known or unknown).

  12. 12
    John West says:

    “If the bubble was pure methane”“these explosions”

    …couldn’t happen. (UEL for methane is 15% at room temperature at 1 atmosphere, perhaps up to (at a stretch) around 18% for conditions described.)

  13. 13
    Andrea Sella says:

    Related to this there’s a rather shrill and to my mind, counter-productive, video out there talking about methane. Unfortunately, although slick and well-intentioned, it adopts a tone precisely counter to the current advice for best practice in the communication of climate science.

  14. 14
    Will says:

    That Shakhova 2010 paper opens with: “The sharp growth in methane emission (50 Gt over 1-5 years) from destructed gas hydrate deposits on the ESS should result in an increase in the global surface temperature by 3.3C by the end of the current century instead of the expected 2C.” I only have access to their two preview pages, so maybe the answer is inside the paper, but I can’t figure out how her team got 2C as the “expected” warming. That also seems to imply that the total warming caused by their hypothetical pulse alone is “only” 1.3C. Can anyone explain how they got that 2C figure, or if I’ve misunderstood something in the admittedly little bit of the paper I’ve been able to read?

  15. 15
    Killian says:

    I’d feel so much better about your continued calm in the face of multiple lines of evidence indicating rapidly increasing methane escaping in the arctic if you were actually researching methane, which you aren’t, so far as I know.

    [Response: My latest research publication is entitled A model of the methane cycle, permafrost, and hydrology of the Siberian continental margin. In review, Biogeosciences Discussions. Don’t know if that counts. David]

    Let’s review he scientifically reticent statements on methane since 2007 or so:

    * It would take 100 years, at least, for seabed methane to destabilize.

    Or, maybe not?

    * Thermokarst lakes probably don’t mean much.

    But now we have have holes blowing out, too?

    * It will take a very long time for widespread CH4 emissions.

    Except it hasn’t. Yes, you are speaking solely in the scientific sense, but it is beyond obvious that has not been appropriate forquite some time. In fact, I am not claiming your analysis I scientificaly incorrect. I *am* saying without consideration of risk assessment and the whole system.

    Your analysis is, as ever, simplistic in the sense I speak of above.

    1. How can we assume 1 Shakhova event?
    2. As the atmosphere and oceans saturate, won’t residence times increase?
    3. As other emissions sources kick in or speed up, do they not reinforce?
    4. What of research showing significant melting of permafrost, inland, at temps similar to today over the last 3 million years or so?
    5. And what of the simple awareness of what happens to systems when all segments are falling apart at the same time?

    And on and on.

    As has been the case before, you address *only* specific aspects of potential CH4 emissions without addressing the whole system.

    What if the Arctic is ice-free in summer the next year or two and the, and the resulting amplification of temps far inland?

    I don’t do6bt your science, but I continue to see little objectivity and systems awareness in these posts. I don’t know you well enough to know if that is a normal mode for you, but it seems pervasive wrt methane emissions and climate urgency.

    Then there’s risk assessment, but that heads to mitigation…

  16. 16
    jyyh says:

    During the Pleistocene-Holocene transition, one possible explanation to the amplification of the ghg-effect could have been the release of South Siberian European and North American (then) permafrost land-based carbon. Seriously hoping for a more mundane explanation for the ending of the ice age. In fact could you do an article on that?

    [Response: If the rise in atmospheric CO2 at the end of the last glacial time had come from organic carbon (trees, peat, dissolved organic matter in the ocean) or especially methane (which is even more isotopically “light” than CO2) it would have left an isotopic signature. What it looks like is that CO2 came from bicarbonate in the ocean, to drive the rise, but no one can figure out quite what changed or why. David]

  17. 17
    Kevin Hester says:

    Sadly we can be certain that there will be no reduction in the CO2 emissions due to an international agreement as our addiction both social and economic is all powerful. The ‘seven sisters’ will simply no allow it and they will fight to the death, ours and theirs, to prevent it. As economic collapse draws ever nearer we will see massive releases due to military attacks on oil fields and infrastructure.
    “let’s assume that the volume of the hole is the same as the volume of the original, now escaped, bubble ” Measuring the volume of release based on the size of the hole seems nonsensical as arterial linkages into this hole could well be immeasurable.I think it is fair to say we have no idea how much methane escaped this hole and others and this relatively new phenomenon is greatly to be feared.

    [Response: Do you think the released methane could be thousands or millions of times higher than the volume of the hole? Seems to me like a long shot from here, that this event could have any global climate significance. Either you need it millions of times larger, or you need millions more of them. David]

  18. 18
    Tim Osborn says:

    Just trying to imagine what 20 million explosions/holes would look like.

    Area of permafrost is a bit less than 20 million km^2. So 20 million such explosions/holes is a bit more than one for every km^2 of permafrost.

    With a diameter of 80 m, one hole for every km^2 of permafrost is about half a percent of the area.

    One every km^2 seems a lot within a few years. What about spread over a 30-year period (one every 30 km^2 per year)? Is that more “feasible”? Given the few reported so far, I doubt that’s much more feasible. With a lifetime of ~10 years, spreading emissions over 30-year period would of course reduce the peak atmospheric burden (though CH4 lifetime would presumably increase with higher CH4 concentration).

  19. 19
    wili says:

    Thanks for the informative reply, David. “high-salinity channels” I hadn’t heard of those. And as for the “pockmarks,” are those the same as the “Pingo-like Features” that were the subject of some discussion a few years ago here, iirc?

    One thing I do agree with Secular Animist on is that in-line responses from scientists are among the best features of this site. So thanks again.

  20. 20
    Andy Revkin says:

    Great to see one of America’s top climatologists putting a lid on Arctic methane hysteria. Click here for more Siberian sense from the only permafrost expert who actually inspected one of the Siberian holes: Fresh Focus on Siberian Permafrost as Hole Count Rises

  21. 21
    MartinJB says:

    Pingos! What a lovely name. For those that are wise in the way of the pingo, could you provide some insight for those of us that are new to their mysteries? Some questions that come to mind:

    How fast does a pingo collapse? It doesn’t look like a rapid process.
    I can see how the melting of the ice lens and destabilization of the earth above could cause a modest depression, but how does the scoured crater and sink-hole-looking formation happen?
    Are pingo collapses likely to contribute substantial methane to the atmosphere?

    Thanks for any illumination you can provide as we strive to become more pingo-savy!

  22. 22
    chriskoz says:

    Tim Osborn,
    “CH4 lifetime would presumably increase with higher CH4 concentration”
    No, CH4 lifetime is a simple exponential decay relative to emissions. So the level of CH4 air concentrations in equilibrium (>10y timeframe) is directly proportional to emissions. The rate of emission from holes popping one at every year as estimated by David above is at least 10000 times smaller than other emissions, e.g. fugitive FF mining and agricultural that are in the order of 100s Mt CH4.

    [Response: Tim is correct. There is a positive feedback of CH4 concentration on it’s own lifetime, which basically means that the more CH4 there is, the longer it lasts. This is not a huge effect, but it does need to be included. It arises from the reduction in OH radical as CH4 oxidation increases. At the highest conceivable CH4 concentration, we estimated that you could increase the lifetime to about 40 years (from about a decade now). – gavin]

  23. 23
    Hank Roberts says:

    > Killian …
    > “… if you were actually researching methane, which you aren’t, so far as I know….”

    You can look this stuff up; “as far as I know” isn’t far — because it’s hindsight.
    “It’s a poor memory that only works backwards”.

    “David Archer” and “methane” returns (in 0.05 sec) about 70 results;
    “as far as I know” is hindsight.

  24. 24

    How would the volume of methane from the amount of hydrates in a hole that size (taking hydrate density into account) compare with the volume of methane you calculated?

    [Response: Great question. Hydrate is condensed phase, so much higher density overall, but it’s only one methane per many water molecules. The density of the gas is much more pressure dependent, so the relative abundances of hydrate vs. gas depends on pressure as well. I know that engineers are considering hydrate for hydrogen storage in cars, etc, so there is a storage advantage to hydrates under some conditions. For this feature, however, I don’t think methane hydrate would have been stable, unless it was deeper than a few hundred meters (depending on the surface temperature. If it had been hydrate, it would not have exploded, but would have taken time and heat energy to melt. David ]

  25. 25
    Lewis Cleverdon says:

    David – some aspects of this strange hole have yet to be discussed, and I’d like to hear your views on them.

    First, assuming the present void was formed by a pingo (for lack of any other known suitable mechanism) it would have been of around 40,000m3 volume. Is this not far larger than any previously found, and also of a novel ratio of depth to width ?

    [Response: I presume so, since it’s in the news, but this is not really my area. There’s a lot of impact of permafrost melting on landforms, coastal erosion and so on. ]

    Second, given that the exposed ground shows the depth of the extant permafrost cap, it seems clear that the pingo’s ice did not melt from the top down, as the surface material remained frozen (gas-tight) before finally being blown out. So are we looking at some geological heat source rather than AGW as the instigator of this event ?
    Third, if pingoes on this scale were present at 20,000,000 sites across the permafrost, they would surely be widely reported by drillers as a common occurrence. As they are not so reported, should we not assume that this hole, and its two smaller local siblings, are an odd and possibly localised phenomena reflecting unusual conditions ?

    [Response: Seems like a reasonable supposition to me.]

    With regard to the combined effects of permafrost and clathrate methane emissions I’m rather less sanguine than you, though I continue to press for the requisite Emissions Control treaty as the paramount mitigation priority. (My apols to any who find this statement shrill or in some way objectionable).

    Shakhova has to have known that she was breaking protocol in proposing a worst case 50Gt CH4 event rather than writing of say a 1.0Gt CH4/yr release from geological seepage stocks trapped beneath perforating seabed permafrost.

    [Response: 1 Gt CH4/yr from the Arctic is still orders of magnitude higher than it is today. ]

    To this extent I’d say that her 2010 paper was somewhat impolitic in raising highly critical opposition rather than constructive discussion.

    [Response: It gets people worried, in my opinion for no solid reason. ]

    What troubles me is that even an all-sources arctic methane release of 1.0Gt per year equates on the 20yr horizon to an additional 84GtCO2e/yr, rising somewhat due to the atmospheric glut effect. Last January’s report of the ’79-’12 satellite record of the Albedo Loss feedback showing it on average to have equalled 25% of the forcing from anthro-CO2, in combination with that level of arctic methane release, would offset our best case of emissions control (of say near-zero by 2050) over three-fold.

    With the observation of six other major feedbacks’ ongoing acceleration mostly from currently small outputs, along with that of a burgeoning number of direct interactive couplings between them, I’m unable to share your view that the fossil fuel industry poses the dominant threat to climate, but would entirely agree that it is the earliest and most controllable threat. Yet even a best case of emissions control would not see the last outputs’ warming realized before the 2080s, giving ~70 yrs of warming for the major interactive feedbacks to gain momentum.

    Addressing the overall threat thus appears to demand not the dismissal of the feedbacks as a minor secondary concern but their citing as justification for the urgent agreement of a protocol within the emissions control treaty for the stringent supervision of geo-engineering research by a mandated scientific agency. Beside being commensurate with the predicament, this approach would also preclude the folly of pretense that Geo-E offers anything more than the essential complement to rapid emissions control.

    [Response: What if we postulate a feedback between ozone depletion, which causes people to get better sun tans, warming the climate due to decreasing planetary albedo? I personally think that’s a negligible effect, but should I argue that it could be thousands of times bigger, making it a good argument against (I guess in this case) ozone depletion? Better to call it small if it looks small, don’t want to be “alarmist”. ]



  26. 26
    Tim Osborn says:


    “Tim is correct… – Gavin”

    :-) Sorry chriskoz, I have an advantage: my first ever published paper was about estimating CH4 lifetime changes according to OH changes determined by CH4 itself (and CO, NOx, NMHCs).

    Osborn TJ and Wigley TML (1994) A simple model for estimating methane concentration and lifetime variations. Climate Dynamics 9 , 181-193.

  27. 27
    Lewis Cleverdon says:

    A typo in mine at #25 is where 40,000m3 should read 400,000m3,
    and an addendum is the reference for the forcing from the Albedo Loss feedback shown in the satellite record:
    “Observational determination of albedo decrease caused by vanishing Arctic sea ice”

  28. 28
    prokaryotes says:

    Lewis, in this video, scientists explain some implications, and in regards to your question about heat transfer/penetration. The hottest years mentioned in the video, are also echoed in the recent Nature study cited above (i.e. Plekhanov and his team believe that it is linked to the abnormally hot Yamal summers of 2012 and 2013).

    I doubt that drillers would find all the holes, potentially formed in recent times, in addition to those observed by chance, the area is huge. My guess is, NASA will probe now for sink formation and similar characteristics.

  29. 29
    chriskoz says:

    Tim Osborn & Gavin,
    My textbook knowledge about OH radicals is: they are plentiful, ensured by production from sun;s photons. It turns out to be a simplistic view that I need to adjust as I learn from your papers and references therein. Thanks for showing me.

  30. 30
    wili says:

    Uh oh. If Refkin is agreeing with Archer now, perhaps Archer is wrong about this after all!? ‘-D

  31. 31
    Morley Sutter says:

    “Siberia has explosion holes in it that smell like methane” – first line.
    Perhaps a minor point but methane is odourless.

  32. 32
    Pete Dunkelberg says:

    Kevin McKinney @4 says:
    14 Aug 2014 at 5:49 AM

    “…the future of Earth’s climate in this century and beyond will be determined mostly by the fossil fuel industry, and not by Arctic methane.”

    “One certainly hopes so,”

    One certainly hopes not!

  33. 33
    Hank Roberts says:

    > emissions control treaty for the stringent supervision of geo-engineering

    Point 1 : stop burning carbon, which is the strongest form of “geo-engineering”

    Look away from the arguments about what should be done,
    and instead look at what’s being done, you know how to find this stuff;
    seabed drilling and pipe-laying are righ now getting far more investment than any non-geoengineering approach.

    This will change the world. In fact it already has.


  34. 34
    Matt says:

    There appears to be two different presentation methods on this article. One version says 1 GTon = 1015 g. The “desktop” version (With the brown bar going down the right side) says 1 GTon = 10 raised to the 15th power.

    [Response: 10 to the 15th power is what’s meant. ]

  35. 35
    Hank Roberts says:

    Honest, there _were_ links behind that colored text when I posted it.
    I checked.
    I suspect there’s a linkovore hiding somewhere in the blog software.
    Let’s see if it’s still hungry:

    You can look this stuff up; “as far as I know” isn’t far — because it’s hindsight.
    It’s a poor memory that only works backwards.

    “David Archer” and “methane” returns (in 0.05 sec) about 70 results

    Meanwhile — how much natural gas is going to be extracted from the area?
    Look it up — many companies and governments are drilling and laying distribution pipelines now.

  36. 36
    Leland Palmer says:

    Wow, that’s an interesting scientific approach to a new phenomenon, assuming that it’s unique (there are now two other examples, by the way) assuming that the emissions were of gaseous methane under pressure rather than solid methane hydrate continuing to dissociate, assuming no methane flows in from surrounding areas, and so on. These appear to be very, very conservative assumptions, and any calculation done under such assumptions will of course lead to a conservative answer.

    But large areas of Siberia are covered with tens of thousands of circular lakes and circular landscape features, and some of them are ten miles or so across. It seems possible that those tens of thousands of circular depressions were generated by similar methane gas eruptions, followed by melting of ice and methane hydrate and subsidence to enlarge the initial gas eruption craters.

    Andrey Plekhanov, Senior Researcher at the State Scientific Centre of Arctic Research, thinks this might be the case:

    “‘I also want to recall a theory that our scientists worked on in the 1980s – it has been left and then forgotten for a number of years.

    ‘The theory was that the number of Yamal lakes formed because of exactly such natural process happening in the permafrost.

    ‘Such kind of processes were taking place about 8,000 years ago. Perhaps they are repeating nowadays. If this theory is confirmed, we can say that we have witnessed a unique natural process that formed the unusual landscape of Yamal peninsula.”

    So, instead of applying your calculation to the current ejection event, maybe it would be better to apply a different, more realistic calculation to the hundreds of thousands of square kilometers of circular Siberian landscape features which could plausibly have been generated by this process. Since erosion might soon erase such landscape features, it seems possible that most of the circular features visible in Google Earth were generated in a burst of methane gas eruption activity a few thousand years ago, perhaps in the early Holocene.

    Perhaps that will still result in a conservative answer. Perhaps, no realistic scenario exists that would release sufficient methane rapidly enough to make a big difference. But, our rate of change of temperatures in the Arctic is very, very rapid, and a similar burst of methane eruptions might occur more rapidly now than in the early Holocene.

    And, of course, these possible widespread methane gas eruptions are not the only change occurring in the Arctic, as permafrost melts and decomposes.

    What do you think are the possibilities of similar eruptions occurring in the shallow waters of the the East Siberian Arctic Shelf, as the shallow underwater permafrost there melts and potentially uncaps more reservoirs of methane?

    The Yamal area gas fields, by the way, have been supplying large quantities of natural gas to Russia and Europe for decades, so there is a lot of methane in the area. In fact, there may be an association between gas fields and these circular landscape features, which should probably be investigated.

  37. 37
    Ruff says:

    Thanks for the article. You are probably right, we should ignore these anomalies that we have never seen before. With out proper study, lasting many years and pear review, how credibly can we take all of the unique and troubling warning signs.

    I too share you concern for the fossil fuel industry. We should, as a planet, maybe send around a some sort of collection tin for them. It is unfortunate that they are so under funded, but hopefully, once all that pesky sea ice is gone we can “drill, baby, drill” them some meager trickle of profitability.

    As I once read – “Sure kids, the planet is now f#$@ked, but for a short, beautiful time, we managed to create real value for our shareholders.”

  38. 38
    Frank says:

    Methane is an odourless gas!

  39. 39
    Mike Coday says:

    I do not that being alarmed about the methane holes in the far north means that we are taking our eye off the real problem of fossil fuels. I don’t this is an either or situation. I think it hurts our movement to move away from fossil fuels to pass on a sense that the methane release from frozen reserves is not a serious concern.

  40. 40
    Jerry Dickens says:

    @wili (#19).

    This is largely unrelated to the initial topic, because the described feature likely has nothing to do with dissociation of gas hydrate, for reasons noted by several people. However, in the spirit of your last sentence, the following it might address several comments in your threads and others.

    There are multiple processes for CH4 passing upward through a regional gas hydrate stability zone (GHSZ).

    The first thing to recognize is that CH4 escapes almost all gas hydrate systems through two mechanisms: 1/ AOM within shallow sediment, and 2/ venting from the seafloor. And it probably should be stated, that in a steady-state world, these outputs are balanced by inputs (methane production), so there is no net carbon gain or loss through escaping methane.

    The first mechanism, which very likely dominates on a global scale, is fairly easy to understand. In most places on continental slopes, gas hydrate does not exist in the upper 10+ meters of sediment (which is another reason for why David is very likely correct in stating that the process of thermal dissociation is slow – heat has to propagate into the sediment). As such, there is a diffusion gradient of dissolved CH4 between the top of gas hydrate and the seafloor. However, the CH4 does not escape the seafloor, because it reacts with SO42- in pore water via anaerobic oxidation of methane (AOM) to generate HCO3-.

    The second mechanism, venting, clearly happens in many locations, although it most likely is not the major CH4 escape path, at least in a steady-state world. The interesting question, as raised, is how methane directly passes through a GHSZ without forming gas hydrate.

    David mentioned two processes, temperature anomalies and salinity anomalies. In some places, notably above faults, there can be upward advection of warm fluids. This leads to a situation whereby the base of the GHSZ is shoaled toward the seafloor. Such shoaling also occurs if rising fluids are very saline, for example above salt diapirs. Great examples of where both processes operate can be found on slopes in the Gulf of Mexico.

    There is, however, an intriguing and different means of a causing a salinity anomaly. This occurs during gas hydrate formation, which excludes dissolved ions. In areas of rapid gas hydrate formation, surrounding pore waters can become very saline, and surpass the point of gas hydrate-free gas equilibrium. Basically, free gas co-exists with gas hydrate and a brine, and no additional gas hydrate can form, because the pore water is too salty. There is good evidence of this occurring in several places, such as Hydrate Ridge, offshore Oregon.

    There is also a third process, whereby during gas hydrate formation, gas hydrate can separate free gas from surrounding water. The idea here is that free gas can move upward within connected space within gas hydrate. There is good evidence of this occurring in several places, such as Hydrate Ridge. Here it should be noted that this process and the above salt-exclusion process may be coupled.

    None of the above addresses the fate of CH4 once it leaves the seafloor. With AOM, excess HCO3- (at least that not precipitating carbonate) leaves the seafloor, so it is not CH4. This is another wonderful topic, but will leave this to another time, other than to state that very little probably enters the atmosphere as CH4.

    As to the other query, pingos, by definition are restricted to permafrost regions, although one might note they can be found in the ocean where permafrost underlies the continental shelf. Some pingos may have led to pockmarks in this type of environment. However, pockmarks can be found in many places where there is no permafrost. Some are likely related to CH4 expulsion, for example on the slopes off west Africa.

    I’ll guess that David’s new paper might include some of this. The suggestion that David is not an expert on methane was a rather silly comment.

  41. 41
    Hank Roberts says:

    Look at the Siberian Times picture, off to the right is another lake with fresh slumping of the banks. Look with Google Earth at the Yamal Peninsula.

    ‘If it was a man-made disaster linked by gas pumping, it would have happened closer to the gas fields’, Andrey Plekhanov told The Siberian Times.
    These are about 30 kilometres away. ‘Gas workers would have been on alert, letting us know about it immediately.’

    a theory that our scientists worked on in the 1980s – it has been left and then forgotten for a number of years.
    ‘The theory was that the number of Yamal lakes formed because of exactly such natural process happening in the permafrost.
    ‘Such kind of processes were taking place about 8,000 years ago. Perhaps they are repeating nowadays. If this theory is confirmed, we can say that we have witnessed a unique natural process that formed the unusual landscape of Yamal peninsula.

    some 10,000 years ago this area was a sea….. Yamal, a large peninsula jutting into Arctic waters, is Russia’s main production area for gas supplied to Europe.

    But looking back, rapid changes were happening:

    Environ. Res. Lett. 4 (October-December 2009) 045004

    Spatial and temporal patterns of greenness on the Yamal Peninsula, Russia: interactions of ecological and social factors affecting the Arctic normalized difference vegetation index

    D A Walker1, M O Leibman2, H E Epstein3, B C Forbes4, U S Bhatt1, M K Raynolds1, J C Comiso5, A A Gubarkov2, A V Khomutov2, G J Jia6, E Kaarlejärvi4, J O Kaplan7, T Kumpula8, P Kuss9, G Matyshak10, N G Moskalenko2, P Orekhov2, V E Romanovsky1, N G Ukraientseva2 and Q Yu3

    1 University of Alaska Fairbanks, Fairbanks, AK, USA
    2 Earth Cryosphere Institute, Russian Academy of Science, Siberian Branch, Tyumen, Russia
    3 University of Virginia, Charlottesville, VA, USA
    4 Arctic Center, University of Lapland, Rovaniemi, Finland
    5 NASA Goddard Space Flight Center, MD, USA
    6 Chinese Academy of Sciences, Institute for Atmospheric Physics, Beijing, People’s Republic of China
    7 Swiss Federal Institute for Forest Snow and Landscape Research, Birmensdorf, Switzerland
    8 University of Joensuu, Joensuu, Finland
    9 University of Berne, Berne, Switzerland
    10 Moscow State University, Moscow, Russia

    Published 15 October 2009

    Abstract. The causes of a greening trend detected in the Arctic using the normalized difference vegetation index (NDVI) are still poorly understood. Changes in NDVI are a result of multiple ecological and social factors that affect tundra net primary productivity. Here we use a 25 year time series of AVHRR-derived NDVI data (AVHRR: advanced very high resolution radiometer), climate analysis, a global geographic information database and ground-based studies to examine the spatial and temporal patterns of vegetation greenness on the Yamal Peninsula, Russia.

    Many of the greenest landscapes on the Yamal are associated with landslides and drainage networks that have resulted from ongoing rapid permafrost degradation. A warming climate and enhanced winter snow are likely to exacerbate positive feedbacks between climate and permafrost thawing….

    This was seabed 8-10,000 years ago — covered with pingos, I expect, like many similar areas around the Arctic Ocean, whether above or below current sea level.

  42. 42
    Hank Roberts says:

    Useful perspective, quoting from:

    Plumes of rising methane bubbles have been mapped off the coast of Svalbard to where the water is about 400 meters deep—the edge of the stability zone for hydrates. In order to find out if these plumes are the result of that recent warming or are simply a feature of the area, a team of researchers led by Christian Berndt of Germany’s GEOMAR Helmholtz Centre for Ocean Research Kiel used a submersible to get a look at the seafloor where the methane is bubbling up.

    There, they found crusts of calcium carbonate formed by bacteria living off the methane. (In fact, there were communities of chemosynthetic bacteria and a kind of tubeworm living at all the methane seeps they visited.) The age of geologically recent, precipitated carbonate in the ocean can be measured using radioactive isotopes of uranium and thorium, so these crusts provided a record of how long methane had been bubbling up at these spots.

    The carbonate turned out to be much older than anthropogenic climate change, with measurements dating them anywhere from 500 years to over 8,000 years old. That means that, at least in the locations they sampled, methane has been bubbling for quite a long time.

    The researchers also made measurements of seasonal water temperature variation and the ability of the sediment to conduct heat, which they used to create a model of the study area. The model showed that there should be a seasonal cycle in the behavior of the shallow-water hydrates just below the seafloor, with some additional hydrates forming while the water temperature is cooler and then melting when the water is warmer. That process could affect the total rate of methane coming up by clearing out pathways to the surface during the warmer part of the year.

    The study allays concerns that these bubbling plumes of methane around Svalbard are a brand-new phenomenon triggered by global warming, but it’s still unknown if the rate of bubbling is changing. The researchers summarize their work by writing that “observations of large contemporary emissions reported in other studies cannot be considered proof of accelerating hydrate destabilization, although neither do they prove that catastrophic destabilization is not accelerating.” Figuring that out will simply take continued monitoring and a better understanding of the conditions on the Arctic seafloor.

    Science, 2014. DOI: 10.1126/science.1246298  (About DOIs).

  43. 43
    Rick Brown says:

    For the apparently metaphor-challenged (e.g. @31, 38): Think of expressions such as “smells like money,” “smells like a scam” or “smells like truth.”

  44. 44
    Hank Roberts says:

    Thank you for the inline responses. (Anyone new to this, don’t forget to scroll back and look for those, they come in a few days or more after the original post, right inline with it). Sanity check especially appreciated.

    One speculation about the shape and depth of the hole:

    Looking at e.g. this discussion:
    GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L01603, doi:10.1029/2006GL027977, 2007
    Origin of pingo-like features on the Beaufort Sea shelf and their possible relationship to decomposing methane gas hydrates

    Remember for a long time “pingos” were surface land features — odd hills on the flat tundra, in areas that that had been under the ice age ice, then had been underwater as that ice melted and sea level rose, then exposed again during the next ice age.

    Then they showed up underwater as well. A puzzlement at the time.

    These authors start by saying

    The Arctic shelf is currently undergoing dramatic thermal changes caused by the continued warming associated with Holocene sea level rise. During this transgression, comparatively warm waters have flooded over cold permafrost areas of the Arctic Shelf. A thermal pulse of more than 10°C is still propagating down into the submerged sediment and may be decomposing gas hydrate as well as permafrost. A search for gas venting on the Arctic
    seafloor focused on pingo-like-features (PLFs) on the Beaufort Sea Shelf because they may be a direct consequence of gas hydrate decomposition at depth.

    … We offer a scenario of how PLFs may be growing offshore as a result of gas pressure associated with gas hydrate decomposition.

    Now those illustrations are again talking about bumps on the surface — like pingos but underwater.

    Look at their illustration Fig. 2, on page L01603, upper left corner.

    The caption says in part:

    s the subsurface warms, the top of the gas hydrate stability zone will move downward. Warming results in gas hydrate decomposition in a gradually thickening zone (brown), releasing gaseous methane into the sediments (yellow). Bubble formation associated with this phase change will create overpressured conditions. (b) Shows how material may flow (red arrows) both laterally and vertically in response to overpressure. Displaced sediments rise upward to form the PLF and allow the gas to vent (VG). As the pressure is dissipated through both the transfer of solids and degassing, subsidence in the area immediately surrounding the PLF (black arrows) creates the moat…

    That’s for pingos underneath the ocean, where slow warming has thawed the seabed — which can collapse into a “moat” — but the material (brown, red arrows) being forced up from below is dense mud and rock and clathrate and ice. And the gas expanding and cooling as the gas expands could push up a mass of ice and reformed hydrates creating the typical “bump” in the seabed. We know that methane will rise up and cool and freeze into fresh clathrates, it clogs up deepsea oil wells routinely.

    But imagine this:

    Here warming now is faster. Think “baked Alaska” — toasty on the outside, frozen on the inside.

    Some warmth gets to the deep source material, however.

    What we’re seeing might be due to much more gas and less solids, pushing up through still hard-frozen material — blowing out a deep narrow hole with mostly gas bubbles and not all that much dirt/rock/ice.

    So — my speculation — maybe instead of pushing up a dome with a mass of ice lifted by the gas, we’re seeing a “Mentos” ebullition.

    That would be gas blowing up through a narrow channel, expanding but not refreezing (maybe with not enough dirt and rock in the mess to freeze around?
    The pressure would end up throwing the surface dirt and plant root layer to the sides, then, as the gas escapes, the remaining froth collapses, leaving a deep hole — the small amount of actual dirt and rock forced up isn’t enough to fill the hole, in this speculation.

    There sure are a lot of round lakes out there.

    And while I thought the Carolina Bays had been well enough explained as astroblemes — could they also have been gas releases?
    I note we’re just now starting to lease the seabed offshore of the Carolinas for more fossil fuel drilling — it’s another rich area.

  45. 45
    Hank Roberts says:

    and then there’s the long-term concerns:

    Ocean oxygen depletion due to decomposition of submarine methane hydrate
    Akitomo Yamamoto1,2,*, Yasuhiro Yamanaka2, Akira Oka1 andAyako Abe-Ouchi1
    Article first published online: 21 JUL 2014
    DOI: 10.1002/2014GL060483

    We have projected the potential impact of oxygen depletion due to methane hydrate decomposition via numerical modeling. We find that the global methane hydrate inventory decreases by approximately 70% (35%) under four times (twice) the atmospheric CO2 concentration and is accompanied by significant global oxygen depletion on a timescale of thousands of years. In particular, we demonstrate the great expansion of suboxic and hypoxic regions, having adverse impact on marine organisms and ocean biogeochemical cycles. This is because hydrate decomposition primarily occurs in the Pacific Ocean, where present-day seawater has low oxygen concentration. Besides the decrease in oxygen solubility and reduced ventilation associated with global warming, the process described in this study is also important in oxygen depletion.

  46. 46
    Lewis Cleverdon says:

    Prokaryotes, thanks for linking the video of Schaefer, Abbot & Miller. It gives the relevant info both that heat is penetrating the deep permafrost faster than was expected, and that the carbon therein is in forms more readily convertible by microbes than was expected. It also reports an expected output of 3.0GtC/yr due to melting, which is almost twice that of the NSIDC study (2011?).

    However it doesn’t give an explanation of how surface heat could have melted a pingo down to ~80ms subsurface surrounded by unmelted permafrost, nor how it could do so while retaining a ~10m gas-tight cap of permafrost over the top.
    This is not to ignore the strong possibility that surface warming weakened the cap enough for high-pressure gas to burst it open, but to refute the possibility of surface warming causing the void that was then mostly emptied of water and filled with gas.

    The idea of the void being a sink-hole faces the problems of its formation through permafrost, and of the lack of any surface water penetration of the solid gas-tight cap – which rather knock this hypothesis. With the impracticality of massed reindeer-peeing playing a role (from aerial images the site is clearly on a regular grazing route) I’m left wondering just what gas presssure would be needed for clathrates to form after a notional influx of hot geological methane melted out a pingo, with sufficient surface warming penetration then causing their destabilization. Which posits a whole series of large IFs . . .



  47. 47
    Lewis Cleverdon says:

    Hank @ 33 –
    > emissions control treaty for the stringent supervision of geo-engineering –

    It’s not at all like you to misquote people intentionally so I take the above to be the result of over-hasty typing. What I wrote was:
    “. . . the urgent agreement of a protocol within the emissions control treaty for the stringent supervision of geo-engineering research by a mandated scientific agency”
    which of course has a radically different meaning. At present the thesis behind this proposal stands unrefuted here on Real Climate as it does on many other public fora across the range of scientific to popular focuses.

    While the global agreement to end fossil fuel dependency plainly will allow the earliest practical action (Geo-E research will take at least years), I think you’re mistaken in stating that fossil carbon combustion is geo-engineering. The widely accepted Royal Society definition speaks of the ‘Intentional’ alteration of the atmosphere ‘For societal benefit’ – which not even the US fossil lobby yet claims for its pollution.

    I see no reason to accept your suggestion of turning away from the issue of what needs to be done to resolve the potentially existential climate predicament. The scale of drilling, pipe-laying etc I do track as a background factor, but the far more troubling issue is for me the fossil lobby’s RD&D efforts. Consider just how much commercial cred fracked gas & oil had 10 yrs ago, and then look at the current worldwide research efforts both on methane hydrates’ extraction and also on coal-seam gasification. Both pose not only vast new accessible reserves but also the prospect of far cheaper outputs than the present deep mining and deep-water drilling operations.

    The fashion for hyping renewables’ rising competitiveness (especially solar PV) wholly ignores this predictable commercial response, just as it ignores the restrictive impacts of intermittency imposing additional storage & distribution costs and, until a binding commensurate global climate treaty is in operation, that of any fossil fuels locally displaced by RE being promptly bought and burnt elsewhere.

    In fact I’d suggest that turning away from a focus on what needs to be done and instead challenging local examples of the global damage is the core of the weakness of public response to the predicament. It is by this lack of specific demands on govt that CoP21 in Paris is on track to discuss merely short-term voluntary ‘pledges’, with the US refusing to discuss the requisite framework for the equitable and efficient allocation of tradable national emission rights under a declining global carbon budget.

    Roll on the day when the scientific community takes this crucial issue to heart.



  48. 48
    Blaine says:

    David: I don’t agree with your assumption that the natural gas leaking from this hole must have been originally in place in the same volume. The natural gas concentration at the bottom of the hole has been measured to be ~10%. The hole is open to the air over approximately a 40 meter diameter surface, and barring absolutely perfect symmetry the wind will generate a vortex over the hole, which would result in mixing on a time scale of around a day or so or faster, even were it some heavier than air gas such as propane. Methane, however, is substantially lighter than air, and a mixture of 90% air and 10% air is dynamically unstable unless the air is warmer by approximately 15C. A smaller difference will lead to active convection. Even were the bottom near freezing, 15C isn’t unusually near the Arctic Ocean at night in summer.

    Assuming that the air was stable when the concentration measurement was taken, it seems reasonable to me to assume a minimum flux of 1 meter of natural gas per day. Across a 40m diameter surface, this is 1250m^3, or 1 ton per day, or 60 tons over a wild estimate of two months that the hole has been there, or 365 tons per year. This is perhaps not a terribly large value, but it is an estimate of the minimum amount of additional leakage from outside entering the hole, which you have assumed to be negligible.

    What about a maximum value? Assuming active convection at 1 meter per second, up over half of the surface and down over half, with a 10% methane concentration, we get a maximum reasonable flux of 60 m^3 per second, or 5 million m^3/day, or 4,000 tons per day, or 1.5 megatons per year. While this may seem small compared to some putative Shakhova event, it’s still around 0.3% of the entire current methane flux of the Earth… from one hole.

    I don’t see the heat shimmer in the video which I would expect if the convection was up near this value. In any case this flux is large enough that satellite methane observations ought to be able to give a tighter upper limit on the flux. I would caution against assuming that most of the flux should flow through spectacular, unusual features like this. The number of features does like this does not put a significant upper bound on methane flux any more than a good estimate of heat loss through geysers puts an upper limit on the geothermal flux of the Earth.

    So, where is all this methane coming from in the first place? Given that the feature is around 30km from the Bovanenkovo Gas Field, which is approximately the 11th largest known natural gas field on Earth, where large-scale commercial production began around 2 years ago, either it is related to natural gas production, or this is a large unexplained coincidence. Yet, doesn’t the fact that the feature is not terribly close to a well site mean that it must be natural?

    Well pipes are sealed with concrete, which is then tested for appropriate pressure reduction along the well string. The assumption is generally made that the surrounding material is, well, rock and not methane hydrates or ice, and will not later melt when production pulls warm natural gas up the well pipe. This assumption has historically generally been correct, but if in fact the field is sealed by methane hydrates near the production casing, the warmer produced gas could melt a path outside the well casing, which might grow larger with time as warmer gas following the path melted a larger path.

    If the gas flows through the top of the main reservoir, but is then capped (presumably by permafrost) in a higher reservoir, it would gradually pressurize this reservoir, spreading farther and farther from the source well. 30km is not an extraordinary distance for a pressure difference to be transmitted in an aquifer, and gas pressure will spread much faster than unconfined water pressure. It’s not what I would have looked for a year ago, but staring at the largest natural gas blowout hole ever observed, I find it much easier to believe that it’s connected to the recent development of a massive natural gas field right next to it, rather than being a natural feature which just happened to appear at the same time and place. In any case, a every natural gas field has a certain amount of other hydrocarbon gasses which act as a fingerprint, and could relatively easily be used to determine if the source of the gas at this hole is in fact Bovanenkovo, or some other source.

    Bovanenkovo itself contains about 7 years of natural gas emissions of the entire Earth. Even if most of this will probably not escape in any eventuality, I think it’s very important to determine as soon as possible whether we’re talking about one well with a bad cement job, one well with methane hydrate melting around it, failure of containment of most wells in Bovanenkovo (which after all will all have much the same conditions at the top of the reservoir), or failure of containment of most wells in the Yamal Project. Confidently stating that we would need 10,000,000 of these events before would have a problem discourages the gathering of very important data and is not helpful.

  49. 49
    Hank Roberts says:

    > emissions control treaty for the stringent supervision of geo-engineering –

    I quoted that fragment because the text seems to assume there is such a thing.
    I’m guessing it’s a hypothetical, something you wish existed — but I’d appreciate a pointer to any reference to such a text or draft.

    I think it would be a good idea, if we recognize that the geoengineering accomplished to date has been done by burning fossil fuel.
    That’s where a treaty needs to begin, I think. Stop going in the wrong direction.

  50. 50

    Continuing #24:

    What if it was a mixture of gas and hydrates? Could it have been an accumulation of gas that then blew some volume of hydrate to the surface where it could melt? If that was the case then I would think there would be a much larger total volume of methane being released.

    [Response: I really don’t think there could have been hydrate above a few hundred meters depth. David]