|Keywords:||risk assessment; fluorine; Hekla; Volcano; Island|
|Full text PDF:||http://rudar.ruc.dk/handle/1800/22706|
Iceland is renowned for its large-scale and frequent volcanic activity, which is due to its unique setting as a subaerial-segment of the mid-Atlantic ridge that is situated above a mantle plume (hotspot). Hekla (locally known as ‘the Gateway to Hell’) is one of the most active volcanoes in Iceland and the erupted magma is known to contain high levels of fluorine. Previous Hekla eruptions have been detrimental to Iceland’s livestock population, with volcanic ash derived fluorine causing fluorosis and sometimes leading to the death of sheep, horses and cattle in areas affected by the tephra fallout. This study investigates the areas of Iceland most likely to be affected by ash deposition from a future Hekla plinian explosive eruption (VEI = 5) and its potential impact on Icelandic livestock, in terms of fluorine poisoning. As well as investigating the frequency of past explosive eruptions from Hekla and the fluorine content of the magma , a risk assessment exercise was carried out using the software Ash3D, which makes it possible to model ash deposition from volcanic eruptions for a given set of meteorological conditions. This investigation used Ash3d to generate 100 model runs for a hypothetical Hekla eruption during the year 2013 using archived meteorological data. The output of the individual model runs are represented by isopach maps for the thickness of the volcanic ash deposits. The isopach data was then used to create volcanic hazard probability maps from a 10 x10 grid identifying the areas in Iceland where livestock are most at risk from fluorine poisoning from a future Hekla eruption. Not surprisingly the livestock population of NW Iceland are at least risk. Our results show that without preventive measures taken, fluorosis is likely to be a major problem for a significant proportion of the Iceland livestock population when the next plinian eruption from Hekla occurs.