<p>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.</p>

<p>Secondly, it was actually a pretty high-volume eruption: per <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1752-699X.2010.00231.x/">Gudmundsson (2011)</a> <em>it has been estimated that it produced 14 km<sup>3</sup> of lava</em> - compare with <a href="https://www.sciencedirect.com/science/article/pii/0377027384900398">the estimated average global rate of magma emplacement and volcanic output</a> of 26-34km<sup>3</sup> per year.</p>

<p>The <a href="http://link.springer.com/article/10.1007/s004450050136#page-1">eruption style</a> 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:</p>

<blockquote>
  <p>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.</p>
</blockquote>

<p>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 (<a href="http://link.springer.com/article/10.1007/s004450050136#page-1">~400ppm</a>).</p>

CC BY-SA 3.0
2014-05-02T13:05:14.480Z
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
CC BY-SA 3.0
2014-05-02T13:12:45.977Z
Iceland and Hawai'i are pretty good candidates for deep plumes :-)
kaberett
CC BY-SA 3.0
2014-05-24T19:06:51.460Z
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):  http://www.worldwaterforum4.org.mx/sessions/FT3_28/Fluoride%20Contamination%20and%20Treatment%20in%20the%20Ethiopian%20Rift%20Valley.pdf
winwaed
CC BY-SA 3.0
2017-08-21T16:46:07.040Z
@kaberett The first link that you provide (Gudmundsson (2011)) is a page not found
ye-ti-800
CC BY-SA 3.0
2014-04-30T23:20:38.160Z
2014-05-01T11:06:17.630Z
2014-05-01T11:06:17.630Z
kaberett
<p>The <a href="http://en.wikipedia.org/wiki/Laki" rel="noreferrer">Laki fissure eruption of 1783/4</a> in Iceland was not particularly large or explosive, but it is infamous for the large quantities of fluorine (or hydrofluoric acid) and SO<sub>2</sub> that it produced, and the resulting local mass poisonings and Europe-wide vog (volcanic smog).</p>

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

<volcanology><volcanic-eruption><vog><hydrofluoric-acid>
Why did the Laki eruption of 1783 produce so much fluorine?
winwaed
# Why did the Laki eruption of 1783 produce so much fluorine?

(Asked by: username_0 on 2014-04-16)

The [Laki fissure eruption of 1783/4](http://en.wikipedia.org/wiki/Laki) 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?

**Tags:** volcanology, volcanic-eruption, vog, hydrofluoric-acid


---

## 1 answers

### Answer by username_1 on 2014-04-30. Score: 12 | Accepted answer

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)](http://onlinelibrary.wiley.com/doi/10.1111/j.1752-699X.2010.00231.x/) *it has been estimated that it produced 14 km3 of lava* - compare with [the estimated average global rate of magma emplacement and volcanic output](https://www.sciencedirect.com/science/article/pii/0377027384900398) of 26-34km3 per year.

The [eruption style](http://link.springer.com/article/10.1007/s004450050136#page-1) 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](http://link.springer.com/article/10.1007/s004450050136#page-1)).

> **Comments:**
> **username_0**: 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)  
> **username_1**: Iceland and Hawai'i are pretty good candidates for deep plumes :-)  
> **username_0**: 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):  http://www.worldwaterforum4.org.mx/sessions/FT3_28/Fluoride%20Contamination%20and%20Treatment%20in%20the%20Ethiopian%20Rift%20Valley.pdf  
> **username_2**: @username_1 The first link that you provide (Gudmundsson (2011)) is a page not found  

---

