This was originally going to be my Ruminarian VIII, but since the whole topic of stratospheric SO2 has been previously covered, I kept it short. If ya want to call it Ruminarian VIIa, I’m okay with that. This one is simply kicking around the potential SO2 of the current eruption.
Throughout Earth’s history, there has always been a “dominant” species. This is typically the species that is best suited to exploit the available resources and either has no predator, or has eliminated/nullified its predators and/or optimized itself to use what resources are available to it. In some cases, over specialization has made it vulnerable to changes in it’s environment, and due to subtle shift in that environment, becomes wiped out. (Typically this is due to the unfortunate convergence of two or more species wide devastating events.) For example, the ongoing Deccan trap eruption coupled with the untimely arrival of a large asteroid at a nearly antipodal position on the Earth. Hello K-T boundary.
There are a few posters here on VolcanoCafe that firmly believe that the Holuhraun eruption will culminate in a new shield volcano. Their reasoning is quite sound, though a few others have alternate opinions about what the end result will be. Supposing that the final magma effusion is on the order of 2 cubic km, with a bit of poking at the data we can get a ballpark figure for what sort of SO2 emission will accompany that. The publication “Preservation of Random Megascale Events on Mars and Earth, Influence on Geologic History.” (edited by Mary G. Chapman) contains a paper by Thordarson et al titled “Effects of megascale eruptions on Earth and Mars” (2009). Figure 6 from that publication presents a graphic representing sulfur content of magma vs the TiO2 to FeO ratio. Cycling that through Dplot and determining the formulaic relationship for fully degassed magma, then running that on the Holuhran geochemical data, I get a value of around 200 ppm by mass for the sulfur release. The resulting SO2 mass is approximately 2 x the mass of the released sulfur. (Oxygen’s standard atomic weight is 15.999, Sulfur is 32.06.) Assuming that the magma from Holuhraun is basalt, it’s mass is about 3100 kg/m³. 2 km³ is 2 x 10^9 m³. Multiplied by the mass, you get 6.20E+12 kg. This would equate to about 1.24E+09 kg of sulfur, or 2.48E+09 kg of SO2. Or 2.48 million metric tones.
That may look big, but reportedly the really large scale events of 1000 km³ or so emit in the range of 5 to 10 gigatonnes. From researching a previous post, I discovered that the sulfate from a stratospheric SO2 injection can linger for around 50 months. So far, the plume from Holuraun hasn’t come anywhere near reaching the stratosphere, and has been a purely troposphere affecting event. In the troposphere, the SO2 is churned around in the relatively turbulent air (the troposphere contains all “weather”) and the moisture acts to leech the SO2 out at a much higher rate than the stratosphere. Yes, there will be more acidic rains due to it, but it will not linger long enough to really affect the climate. Many years ago, I moved a plant from one part of my yard to another. Concerned about what the plant needed to thrive, I found out that Azaleas love acidic, well drained soil. In the grand scheme of things, this means that any Holuraun SO2 that doesn’t burn the leaves, should make them healthier, giving the roots a more favorable soil. Will they go on to become the dominant species? Beats me, but to be safe, let’s just be nice to our future Azalean overlords. Keep em watered and they may in turn keep thee!
On behalf of our Future Azalean Overlords,
Reader-participation article, invitation for YOUR contributions!
One of the delights of reading the comments section are the many scenarios, ideas and interpretations our readers come up with. As there is merit to most of them, Dragon Kilgharrah has decided that she will collect your entries and select the most interesting and intriguing of those for next Friday’s VC article. In order not to inundate Kilgharrah with a flood of papers a million words or more and in order to give her a chance to sort through your contributions, please try and keep within these limits:
- Your proposal should be no more than 500 words long and supported by no more than two graphic representations or pictures
- You email your entry to firstname.lastname@example.org who will pass it on to Kilgharrah in the Den
- Wednesday 24.00 UT/GMT is the deadline
Be creative in your thinking but not “too creative”! Your idea of what will happen should ideally be within the realms of the possible, so perhaps a few reminders are in place:
- We are dealing with a very large volcanic system, known to have set off large eruptions at great distances from the main vent such as the Torfájökull eruption of 1477 and the Veidivötn eruption of 1480. Bardarbunga is situated where the Mid-Atlantic Ridge splits the North American and Eurasian continental plates and directly above the centre of the inferred Icelandic Hot Spot.
- The Holuhraun eruption is fed by magma from the reservoirs of Bardarbunga. In spite of Ármann Höskuldsson being (mis-)quoted as saying that the temperature is some “200°C higher” for a basaltic eruption, the 1147-1188°C as measured at the vent is actually some 100 – 200°C lower than it would be if it was juvenile magma direct from the mantle. Also, the chemical composition is such that it has sat for a while, cooling and begun to fractionate.
- The crust is considered to be up to 40 km thick even if it is suspected that it is much thinner directly underneath Bardarbunga, perhaps no more than 20 km. Thus the Holuhraun while forming a shield is not yet a shield volcano in the making as it has no independent supply of magma. In order to do that, it must break through to a depth of some 30 – 40 kilometres and this far, the deepest nearby quakes have been placed at 22.5 km.
- The total amount of seismic energy released in the form of earthquakes, to date in excess of 400 TJ, TeraJoules (1 TJ = 1,000,000,000,000 joules), is equal to a single magnitude 6.5 earthquake such as the Eureka earthquake (California, USA), 2010. In spite of the awe-inspiring number of earthquakes greater than magnitude 3.0, even in spite of the very great number of magnitude 5.0 to 5.7 earthquakes (1,000 to 10,000 times more powerful than a “mere” M 3.0), remember that we are dealing with the movement of so many tens of thousands of cubic kilometres of bedrock that it truly boggles the mind.
- The subsidence of the caldera is real. It cannot be explained by loss of volume due to melting ice as the energy requirement for such a glacial melting would be enough for at the very least a M 10.5 earthquake or roughly 1,000,000 greater than the cumulative seismic moment for the entire Bardarbunga crisis!
Hopefully, we will all have a very interesting read come Friday and who knows? Amongst those may be one contribution that predicts and explain the exact course of events! If all goes well, on Sunday November 30th, Carl will as promised give us his analysis of “What is going on at Bardarbunga”. So sharpen your brains and break out those plots!
Please remember the Wednesday November 26th deadline!
Pyrite & Kilgharrah