The Laki fissure eruption of 1783/4 in Iceland was not particularly large or explosive, but it is infamous for the large quantities of fluorine (or hydrofluoric acid) and SO2 that it produced, and the resulting local mass poisonings and Europe-wide vog (volcanic smog).

How come a number of Icelandic volcanoes are capable of producing hydrofluoric acid in such large quantities?

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    There is some interesting stuff in this research paper that might supply some answers. You just need to click on the "full view" to the left to see the entire article. It seems as if it was some eruption.... – user136 Apr 17 '14 at 17:53
up vote 12 down vote accepted

First things first about Laki: it's in Iceland, which means its source is a combination of an ocean ridge and a mantle plume. The plume contribution means that the source composition is relatively undegassed (unlike the source for most mid-ocean-ridge basalts (MORBs)!) and very basic, so contains relatively high concentrations of sulphur and other volatiles.

Secondly, it was actually a pretty high-volume eruption: per Gudmundsson (2011) it has been estimated that it produced 14 km3 of lava - compare with the estimated average global rate of magma emplacement and volcanic output of 26-34km3 per year.

The eruption style during the Laki eruption - not dissimilar to other Icelandic eruptions - is believed to have promoted volatile emissions during the eruption, including liberating up to 50% of F originally dissolved in the melt:

The high degree of degassing at the vents is attributed to development of a separated two-phase flow in the upper magma conduit, and implies that high-discharge basaltic eruptions such as Laki are able to loft huge quantities of gas to altitudes where the resulting aerosols can reside for months or even 1–2 years.

Thus the significant fluorine release at Laki seems to have been due to a large-volume eruption degassing halogens extremely efficiently, with a relatively high initial fluorine concentration in the melt (~400ppm).

  • So high amount of F in the source mantle implying a deep source - says something for the deep plume vs shallow mantle hotspot debate! And then followed by efficient degassing (low viscosity, large lava flows, etc) – winwaed May 2 '14 at 13:05
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    Iceland and Hawai'i are pretty good candidates for deep plumes :-) – kaberett May 2 '14 at 13:12
  • Following up on F coming from the deep mantle, I've just found that groundwater in the Danakil Depression (another possible mantle plume) also has high F levels. So much so that it will weaken teeth (ie. a lot more than dental fluoride): worldwaterforum4.org.mx/sessions/FT3_28/… – winwaed May 24 '14 at 19:06
  • @kaberett The first link that you provide (Gudmundsson (2011)) is a page not found – ye-ti-800 Aug 21 '17 at 16:46

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