Iceland’s Laki Fissure Eruption of 1783


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Laki Lava Flows in Iceland: Photo by Ulrich Latzenhofer

Iceland is a volcanic engine. The eruptions of the Eyafjallajokull volcano in 2010, and Grimsvotn a year later, caused massive disruption to transport networks through Europe, and accompanying economic impacts. But eruptions of Iceland’s many volcanoes are nothing new and in fact the recent volcanic activity on the island, though it makes the news headlines, has been relatively low-impact compared with events in the past.

The Laki Fissure Eruption of 1783

There are two types of volcano – those which occur along the edges of the world’s tectonic plates and those which occur above so-called ‘hot spots’, where molten rock reaches unusually far upwards from the Earth’s mantle to its crust. Iceland is unique in that it is the product of a hot spot which underlies the Mid-Atlantic ridge – the only place where both conditions for volcanism occur together. As a result it is exceptionally volcanically active.

Fissure eruptions are defined as linear fractures in the Earth’s surface where lava erupts over a larger area (Oxford Dictionary of Earth Sciences). As a result they are capable of emitting enormous quantities of lava. Fissure eruptions are so closely associated with Iceland that they are also known as Icelandic eruptions. It is at Laki, in southern Iceland, that one of the most significant volcanic events of the modern era took place.

The Open University’s coursebook, Earth and Life: The Dynamic Earth indicates that the Laki event involved eruptions over a length of 25-27 km from more than 140 separate volcanic vents and erupted only an estimated 14 cubic km of lava. It is by no means the largest event ever to take place – the series of eruptions generating the Columbia River Province in the USA, for example, produced 170,000 cubic km of lava over a period of two million years.

Iceland from Space: image by Jacques Descloitres/NASA Visible Earth

Iceland from Space: image by Jacques Descloitres/NASA Visible Earth

Though small in the greater scheme of things, Laki is nevertheless significant and relevant in that it is the largest lava flow of modern times. The eruption, associated with a present-day volcano known as Grimsvotn which erupted as recently as May 2011, began in June 1783 and continued for seven months (Smithsonian Institute). Its environmental consequences were devastating.

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