Liquid hot magma
For some reason I automatically read that with a Dr Evil voice.
Liquid hot magma from the Earth's mantle can shoot up to the surface via a "highway from hell" over just a few weeks, volcanologists have discovered. Boffins studying the Irazú stratovolcano in Costa Rica, and specifically its eruption between 1963 and 1965, found the first hard evidence of high-speed magma ascents. This …
Whenever I see that, I chuckle.
Magma is by nature hot. It's under immense pressure. Release pressure, that which might only be plastic ends up mixed gas and liquid matter.
I'll not go into local mixing due to oceanic pressure on the mass' movement upwards and the contribution of water to eruptions.
It's long been deduced that magma from very deep in the earth must occasionally come to the surface very quickly. Diamond is a stable form of Carbon only at very high pressure (>50km deep, ISTR). If magma containing diamond rises slowly, the heat and reducing pressure will decompose the diamond into graphite. It has to rise fast and cool fast, to freeze the Carbon as metastable diamond.
Diamond is associated with the igneous rock Kimberlite, and no Kimberlite erruption has taken place in recent geological history. This is possibly a good thing. They may be extremely violent events and/or happen unexpectedly at a location with no extant volcano.
“The study provides one more piece of evidence that it’s possible to get magma from the mantle to the surface in very short order,”
So when can scientists arrange for this to be delivered to my barbeque at say 7 o'clock each evening, on sunny evenings only of course, ready for me to put on the dinner?
A study (that I have only heard of, not read yet) suggest that Grímsvötn volcano eruption 2011 was due the same phenomenon. A new influx of magma at depth started the largest eruption in that volcano for 140 years and creating a ash cloud that did go up to 20 km in the air.
If that is going to happen again in Iceland I do not know, but I am keeping a eye on it as is.
I think this is the paper you want:
Maﬁc intrusions triggering eruptions in Iceland by O. Sigmarsson
Similar triggers have been proposed for the Soufriere Hills eruption on Montserrat which seems to have had a relatively cool, mostly crystalline magma chamber that then received an injection of very hot mafic material. That created local melting, parts of the crystal slush in the chamber largely melted, became mobile and began to move up towards the surface.
Injections of magma are well-known to trigger eruptions - new material can simply overpressurise the magma chamber, the heat can cause a greater degree of melting and more mobile magma, it can cause gases to exsolve from the magma, or it can introduce new gases into the chamber.
The paper says it takes months to years for the magma to reach the magma chamber with some indication that faster ascent occurred later in the eruption. Still fast, but not quite as dramatic.
The geochemistry is quite unusual. Had the magma hung around in the crust it should have relatively low olivine (it fractionates out very early) and any residual olivine would have been iron-rich (low forsterite) since magnesium olivine crystallises at a higher temperature. Low olivine usually means low nickel (Ni is incorporated into olivine crystals), but this eruption had very high concentrations magnesium-rich olivine and lots and lots of nickel. So it must have come straight up from the Mantle.
Fast-moving, deep-seated magma is found in places like the African rift where you get weird eruptions of low-silica, nickel-rich magmas such as sodic carbonatites (practically molten washing soda) and nephelinites; but in many cases the very hot magma rising from the Mantle begins to digest the crust around the fissure or vent and you end up with highly contaminated magmas that are chemically quite different from their original primitive magmas.
Good paper all round!
The word crust is really idyllic. Magma translates up through dikes and sills which are cracks and voids in the country rock. Remember Crack in the World and Journey to the Center of the Earth? Since these natural magma rivers are already present all the magma has to do is follow the path of least resistance. The more interesting question would be why is not their more active volcanos? Maybe that's because the Earth is done with mega-eruptions like kimberlites and has settled into tectonic contraction. Whats an undersea volcano called anyway? Marecano?
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