It’s a gas… Musings on Volcanic SO2

SO2 is a volcanic gas (along with a lot of others) but specifically , SO2. SO2 is a high heat product… H2S is a low heat product. You can tell the difference by the smell. Burnt match smell, SO2, rotten eggs, H2S. Don’t run around sniffing for them, both can be lethal, and H2S deadens your sense of smell. SO2 turns to acid in your mucus membranes… specifically H2SO4. And that’s not a good thing.

But… that H2SO4 bit is important.

In the troposphere, where all the weather happens, H2SO4 yields “VOG” .. “Volcanic Fog.” In LA, they coined the phrase SMOG… essentially the same thing but with a little auto exhaust thrown in for good measure. It’s a pollutant, and tends to trap heat.

In the stratosphere, up above where all the weather occurs, H2SO4 acts as an umbrella, blocking sunlight and cooling things off.

A couple of days ago, a paper was linked here that addressed this issue, and noted a seeming connection with CO2 and the scavenging rates of both gases from the atmosphere by OH, the friendly hydroxyl radical. (it is the pre-eminent free radical that we try to avoid in our diets)

Side Note: Nitric oxide - NO, is the other one
that we are usually concerned with ... oddly enough,
it's also the active ingredient in Viagra. So if you
are shunning free radicals in your diet, but are
munching Viagra, that sort of defeats the purpose.

At least you will enjoy yourself.

Now… it’s been a lot of years since I took chemistry, but I was trying to figure out the dynamics of SO2 to H2SO4 production. I used several chemical equation balancing programs… but they all come up with a weird issue in the of O2. Looking into it, it turns out the SO2 + H2O will produce sulfurous acid and not sulfuric acid. In order to get sulfuric acid, there has to be a catalyst. If you remember, a catalyst enhances a reaction rate though it is not destroyed by the reaction. (such as the platinum beads in your cars catalytic converter). In this case, the major catalyst is NO2, or Nitrogen dioxide. Nitrogen dioxide comes about from the O2 (oxygen) and N2 (nitrogen gas) reacting in a high heat environment… such as lightning strikes, combustion engines, and volcanic eruptions.

When an eruption occurs, there is an emission of SO2, it gets converted over to H2SO4, and if it makes it to the stratosphere, acts as a radiation shield blocking sunlight. How much gets that high up, depends on how much is released in the eruption, how fast it gets leached out of the column by the ambient humidity and the availability of NO2. That that is leached out of the column becomes tropospheric H2SO4 if it leaves the column and doesn’t make the trip the rest of the way above the tropopause.

I read a paper a while back… don’t have a link to it, but the paper indicated that tropical eruptions have a much greater leach rate than the higher latitude eruptions. They also have a thicker troposphere to punch through to reach the stratosphere.

Latitude vs Holocene Volcano Count

From KarenZ, some links if you want to rummage around in some of the info about the gases

A USGS article about SO2

There was a paper that I was after, but could not readily locate, that dealt with a proposed scale for volcanic SO2.  I was able to find a related bit of info here

Note specifically, table 3-2. VSI to VEI.

VSI was designed to fit the VEI scale so that you could get a quick and dirty, but relatively reasonable estimate of the SO2 emission of a Volcanic eruption. The scales are different for Arc (such as Tongario) and non Arc volcanoes.

“Chapter 11.A Volcanoes -EMEP/EEA emission inventory guidebook 2009″

Now… a “rickety segue” to the tropopause.  It goes well with the first plot of the number of Holocene volcanoes vs latitude.  This is a reworked plot from a few months ago.  I took about 5 years of tropopause info and averaged it out on a month by month basis.

Tropopause Height

Before anyone beats me up about the prevailing conditions driving whether or not a plume crosses the tropopause and makes it to the Stratosphere, I understand that.  This is just a general guide so that you know about what altitude the tropopause will be at.

Note: the “rickety segue” phrase is from a Frank Zappa concert as he introduced the next song in the set.


320 thoughts on “It’s a gas… Musings on Volcanic SO2

  1. Serendipity…

    At 1514 UT on February 28 a NASA research aircraft (on the SOLVE field experiment), with a variety of advanced sampling equipment on board, unintentionally encountered this volcanic cloud. This has resulted in an important validation opportunity for remote sensing, because we can not only compare independent satellite data and trajectory model results (Figure 3), but we also have direct sampling data from the aircraft transects. Studies of the dynamic process of atmospheric injection are vital if we are to understand the potentially large effects of large eruptions on the Earth’s atmosphere. The remote sensing approach, applied to eruptions of smaller scale, is very likely to illuminate the process.

    That was Hekla 2000.


    • Lurking, Could i place the special plots page in Gems into your caring hands?
      You know better which plots are worth storing.
      (@all who have not yet discovered this page… ->Gems ->special plots page)

      Micrsoscopic images is in Gems too and i uploaded almost all SEMs i have from all volcanic probes i have so far. The none-volcanic stuff still goes to my flickr

  2. There have been 19 earthquakes already this morning until 03:59 all small in magnitude and below 13km except for one the strongest a 1.6 which was at 19km deep.

    The location still seems to be centered around Tanganasoga between co-ordinates

    27.7407 -18.0710 and 27.7568 -18.0524.

  3. 2 more EQ’S and they seem to be picking up in strength.

    1161327 16/08/2012 04:02:49 27.7683 -18.0781 11 1.5 4 W FRONTERA.IHI
    1161328 16/08/2012 04:28:39 27.7685 -18.0774 10 1.4 4 W FRONTERA.IHI

  4. Thanks Lurking. Interesting! Look at the elevated levels for the Antarctic during winter. Do you think this is the result of Mt Eribus & Co? but why winter?

      • OH! Baste my flaming Dumplings!!!! 😡
        I have urgent work do do this morning. Yesterday my PC (I suspect it was Internet provider now) would not download required scans. I sat up until 3.00am sorting out the problems.
        PC is running sweetly now but,,,,,
        Photobucket where I store my public photos for using with URLS is now down for maintenance! I cannot list my items which I must do today or I will have a horrendous backlog.
        Time for another coffee………

    • No that is due to this being the warmest year on record in the arctic.
      And to prove that you should never look at local weather, at the same time and during the same warmest year the glacier ontop of Swedens highest mountain decided to grow with 2,8 meters. Why now? Because of the massively increased amounts of snow falling ontop of it. Glaciers grow for two reasons, either colder climate, or more precipitation. And we had loads of snow this year, more then ever. Who now? Well, heat equals water boiling off the oceans, then the same airborne water comes slaming into norway, get’s cooled down, and starts to drop… Sigh… I hate water falling down.

      • Latest two quakes on El Hierro as Judith has already pointed out are small but shallow. The last one is only 12km.

          • animals are a lot more sensitive to their surroundings, they most likely pick up HT, also humans seem to be affected in the last week or so, instinct of survival I suppose

          • Local people on El Hierro are commenting on Avcan facebook they feel dizzy as if on a ship, smell bad eggs,Tigaday does not now stop vibrating, dogs are howling . They are certainly feeling the tremors again and they are unhappy that nobody is listening to them .
            One lady pointed out that her grandparents experienced years of siesmicity before the actual eruption on La Palma in 1939 so try to stay calm.

  5. Hey, remember the ash of eyjafjalla post on may 8. There will be an article in the newspaper about it. I am going to be interviewed.
    Of course the blog will get a mention, lets see if we get more austrian visitors too then.

  6. GeoLurking yesterday about earthquake pattern El Golfo area: “The more I look at that the more I see ring structures/alignments.” (20:19) and “Maybe those really are ring faults…” (20:34).

    His words remind me of the pictures of the “Cracking and subsidence of the Mýrdalsjökull glacier around an ice cauldron above the Katla caldera”, see GVP:
    figure 42:

    Could it be that rock cracks in the same way as ice around a subsiding (or alternately subsiding and rising) center?

  7. If you look at the global volcanism program today, you’ll notice they put Harve seamount in the sidebar (volcano news) but not in their weekly report. I sent them some info on Havre seamount to them today for when they add it to their list 😉

  8. To everybody!

    The comment system has had a critical failure, it is temporarily impossible to post replies to comments, instead they will slide forward to the last position and be presented as a new comment. has been informed of the problem.

    Hope that this will not cause to much inconvenience.
    Kindest Regards

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