The consequences for Iceland, known as the "Móðuharðindin" (Mist Hardships), were catastrophic.[9] An estimated 20–25% of the population died in the famine and fluoride poisoning after the fissure eruptions ensued. Around 80% of sheep, 50% of cattle and 50% of horses died because of dental fluorosis and skeletal fluorosis from the 8 million tons of hydrogen fluoride that were released.[10][11]
The parish priest and dean of Vestur-Skaftafellssýsla, Jón Steingrímsson (1728–1791), grew famous because of the eldmessa ("fire sermon") that he delivered on 20 July 1783. The people of the small settlement of Kirkjubæjarklaustur were worshipping while the village was endangered by a lava stream, which ceased to flow not far from town, with the townsfolk still in church.
"This past week, and the two prior to it, more poison fell from the sky than words can describe: ash, volcanic hairs, rain full of sulfur and saltpeter, all of it mixed with sand. The snouts, nostrils, and feet of livestock grazing or walking on the grass turned bright yellow and raw. All water went tepid and light blue in color and gravel slides turned gray. All the earth's plants burned, withered and turned gray, one after another, as the fire increased and neared the settlements