What disaster caused famine and killed one-fifth of Iceland’s population in the 1780s?

The famine that devastated Iceland in the 1780s was caused by the catastrophic eruption of the Laki volcanic fissure.

Beginning in June 1783 and lasting until February 1784, this event is considered the greatest lava eruption on Earth in historical times. The eruption released massive quantities of sulfurous gases, which stunted crops and grasses and killed the majority of the country's domestic livestock. This environmental disaster, known as the Haze Famine, resulted in the deaths of approximately one-fifth of Iceland’s population. The climatic impact of the eruption was widespread, contributing to food shortages and poor harvests across Europe as well.12