A magma chamber’s ebb and flow


If you ever want your research to be picked up by the popular press, you pretty much need to publish in the journal Science. It (along with Nature) are seen as the Premier League of scientific publication, and even though there isn’t a lot of agreement on whether what gets published in these journals is the best science has to offer (or whether it is just the most flashy), it definitely gets the press’ attention.
Right now, there has been a lot of noise in the science press about a recent article that discusses predicting volcanic eruption. This research on Montserrat in the West Indies, brought to us by researchers from Penn State, Univ. of Arkansas and Univ. of East Anglia, looks at the cycles of activity at Soufriere Hills Volcano. The long-and-short of this work is that volcanoes aren’t being filled with periodic influxes of magma right before an eruption, rather that volcanoes get a constant flux of magma that is then stored at different levels in the magmatic system. The researchers determined this by examining both the eruption rates and ground surface deformation at Soufriere Hills.
This would suggest to me that the dynamics of the magmatic plumbing is what dictates the periods of eruption and repose, which in a sense, isn’t entirely surprising. Rather than evoking a model where magma has to stop and start magma generation at depth, we have a system that is more or less “clogged” or “unclogged,” where magma is constantly being brought up from depth into a deep and shallow reservoir. Tiered magma chamber models like this have been suggested before, but it is hard to actually “see” these (geophysically or seismically) under a volcano. Now, the question of why the magma gets stored at different levels and in what state that magma is in (liquid? mush? both?) is a whole different story, but at least this is a start in trying to coax out the long-term state of a magmatic system during both active and inactive periods of a volcano.

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3 thoughts on “A magma chamber’s ebb and flow

  1. Eric, as someone who tries to think like a physicist about all natural phenomena, I’ve wondered for some time about all this talk about “magma chambers” – are you volcanologists still using a language based on pre-continental-drift concepts decades after continental drift and plate tectonics has been well and truly proved? I’m sure you’re not stuck in the past with Sir Harold Jeffreys, but your terminology still bears an echo of his theories, suggesting that volcanoes are formed by some mysterious process of a liquor forming in a magician’s retort in a static continent.
    Now that it’s clear that, apart from the ones at the mid-ocean rifts, volcanoes occur over subduction zones, I presume that the ‘magma’ is the lighter material, or the non-siderophilic material, that separates out and ‘tries’ (to personify it a bit) to stop being subducted? Therefore I’d expect that there would be a longish linear feature at a certain depth where the stuff we call magma separates out from the descending plate. Then of course where it comes up to the surface depends on weaknesses in the overlying crust, and once there has been an eruption in one place the weakness will remain and there’ll be a channel to the surface. That seems to be consistent with the finding reported here – a model ‘where magma is constantly being brought up from depth’ and whether it flows steadily or erupts explosively depends on the vagaries of the higher structures. I’m quite unsurprised by that finding. Can I respectfully suggest that there ought to be more dialogue between the large-scale plate tectonics people and those of you who focus on volcanoes, one mountain at a time? And that you should see a ‘volcano’ as something that starts a few hundred miles away at the place where one plate starts to sink under another?
    Big-Picture Pykie

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