The hardship began with the eruption of the volcano in Lakagígar on June 8, 1783, which was one of the greatest volcanic eruptions in historical times. The eruption devastated Iceland and the environmental effects could be felt in many places throughout the world, due to the severe global meteorological effects of the rising sulphuric fumes. Jón Steingrímsson, a local Lutheran pastor, grew famous because of his eldmessa ("Sermon of Fire"), which he delivered as his congregation took refuge in the town church. His sermon was credited with stopping the advance of the lava flow. It was later printed as Eldrit in 1788.
After the volcano erupted, it emitted a lava flow which lasted for about five months. Additionally, and even more devastatingly, there was a poisonous mist of fluorine and sulfur dioxide which settled over the entire country, burning up grazing lands and killing livestock, which lasted far longer. It is believed that up to 80 percent of livestock died, and an estimated one-fifth of the human population of Iceland (approximately 10,000 people) perished from the combined effects of the mists and the resulting famine. It is estimated that 14 cubic kilometers of molten lava flowed from the volcano, making the eruption the world's largest recorded lava flow.