The 'Laki eruption' of 1783–1784 occurred in an ice-free portion of the Grímsvötn volcanic system in the Eastern Volcanic Zone (EVZ) of Iceland. The name Laki comes from a nearby mountain, and the eruption was in fact known as the 'Skaftáreldar' (Skaftár Fires) in Iceland. The Grímsvötn volcanic system is the most frequently active volcanic system in Iceland with about 70 eruptions in the last c.1130 years (Thordarson and Larsen, 2007). The Grímsvötn volcanic system last erupted in May 2011.
The Laki eruption was the second largest volume eruption in the last 1130 years in Iceland.
Thordarson and Self (1993, 2003) gave detailed analysis of the eruption: The eruption began on 8th June 1783 and lasted eight months. It occurred as ten pulses of activity, each starting with a short-lived explosive phase followed by a long-lived period of fire-fountaining. Each pulse was associated with the opening of a fissure, and by the end of the eruption, the fissures extended for 27 km. The eruption produced approximately 15 km3 of lava that flowed to cover an area of approximately 565 km2, and produced about 0.4 km3 of tephra (rock fragments and particles). This was the second largest basaltic lava flow in Iceland in historical times. The eruption emitted about 122 megatons of sulphur dioxide into the atmosphere (Thordarson et al., 1996) which reacted in the atmosphere to form about 200 megatons of sulphuric acid aerosols (Thordarson and Self, 2003).
The impacts of the Laki eruption were felt most severely in Iceland, where more than 60% of the grazing livestock was killed by fluorosis. The resulting illness, famine and environmental stress caused the death of about 20% of the Icelandic population (Thordarson and Self, 2003 and references therein).
This type of eruption is characterised by huge outpourings of lava and volcanic gases. These gases convert in the atmosphere to aerosols which can cause regional hemispheric impacts.
There were reports across Europe of an atmospheric haze and 'dry sulphurous fog' in 1783 which were almost certainly associated with volcanic aerosols and possibly gases. Thordarson and Self (2003) present numerous observations of the atmospheric and environmental effects of the eruption. Meteorological records also show that the summer of 1783 was unusually hot and was followed by an exceptionally cold winter; although it cannot be proven that this was related to the eruption.
Contemporary records from England and other European countrues demonstrate some environmental and health impacts such as outdoor workers suffering respiratory difficulties and crop and vegetation damage (e.g. Grattan et al., 2003). Several published studies, including Witham and Oppenheimer (2004), demonstrate two periods of crisis mortality in England during the Laki eruption; however, it's not possible to directly ascribe these to the Laki eruption.
The largest fissure eruption in historical times in Iceland was the Eldgja eruption in 934-938 AD, from the Katla volcanic system. More than 18 km3 of lava was produced and more than 1 km3 of tephra, as fissures opened up along a total length of 75 km (Thordarson et al., 2001). Some of the fissures opened below ice sheets which may explain the large volume of tephra.
In total, there have been four large volume fissure eruptions in historical times (since late 9th century) with erupted volumes greater than 4 km3. So, these eruptions are not frequent and yet we know that the last of these, the Laki eruption, led to severe impacts on Iceland and beyond.
There will be fissure eruptions in the future, although it is not possible to say exactly where or exactly what size the next one will be. Modern monitoring techniques employed by the Iceland Meteorological Office mean that we will likely have some warning before an eruption, but it may not be possible to foresee the eventual scale of such an event at its onset.
The planning process for such an eruption relies on improving understanding of how the modern world might be affected. Such work requires transdisciplinary science and the engagement of the many sectors, from health to transport, that might be affected.
Contact Dr Sue Loughlin for more information on the Laki eruption or the Grímsvötn volcanic system.
Grattan, J, Durand, M, Taylor, S. 2003. Illness and elevated human mortality in Europe coincident with the Laki fissure eruption. In: C Oppenheimer, D M Pyle, J Barclay (Eds), Geological Society Special Publication, 213, p401-414.
Thordarson, T & Self, S. 1993. The Laki (Skaftár Fires) and Grímsvötn eruptions in 1783-1785. Bulletin of Volcanology, 55, p233-225.
Thordarson, T, Self, S, Óskarsson, N, Hulsebosch, T. 1996. Sulphur, chlorine, and fluorine degassing and atmospheric loading by the 1783-1784 AD Laki (Skaftár Fires) eruption in Iceland. Bulletin of Volcanology, 58, p205-225.
Thordarson, T & Self, S. 2003. Atmospheric and environmental effects of the 1783-1784 Laki eruption: a review and reassessment. Journal of Geophysical Research, 108, D1.
Thordarson, T & Larsen, G. 2007. Volcanism in Iceland in historical time: Volcano types, eruption styles and eruptive history. Journal of Geodynamics, 43, p118-152.
Witham, C S & Oppenheimer, C. 2004. Mortality in England during the 1783-4 Laki Craters eruption. Bulletin of Volcanology, 67, p15-26.