• Matthew Blackett

The last time Iceland 'flooded' with lava

Many eyes of the world have been focused on #Fagradalsfjall volcano in #Iceland, witnessing its prolonged effusion of lava that has continued unabated since mid March 2021. Older readers (and avid volcano enthusiasts) however, might well remember, or have heard of, another volcanic episode in Iceland that happened in 1973. This earlier episode however, was unlike the current one in that it started with little warning and actually did destroy homes and people's livelihoods. The 1973 event was attributable to a fissure eruption on the island of #Haimaey and just outside the small fishing town of #Vestmannaeyjar.

Fissure at Eldfell volcano, with the town of Vestmannaeyjar in the foreground (source: Eldheimar Musuem).

Haimaey is the largest island of the Vestmannaeyjar archapeligo (see maps below), set off the southwestern coast of Iceland. In the middle of the night on 23 January 1973, a fissure opened up to the south east of the island's main town, Vestmannaeyjar, with no warning whatsoever, ultimately forming a new volcanic landform that was (controversially) named #Eldfell volcano. Most of the island's residents were rapidly evacuated after sirens sounded and what followed was an eruption that lasted for 5 months, completely disrupting the lives of the island's residents. Indeed, the the main concern at the time was the fact that Vestmannaeyjar was (and remains) a significant fishing port, with fishing being the island's main source of income. If the town and/or port were destroyed, what future was there for the island?

Satellite image of Heimaey Island on 24 May 2021 (source: Planet, @planet, #planet)

The Vestmannaeyjar archapeligo off the southeaster coast of Iceland.

As the eruption proceeded over the coming months, the outskirts of the town were inundated with lava, whilst those parts which avoided direct inundation were often choked with ash fallout instead (see images below).

Homes burried by ash (Source: CC BY-SA Christian Bickel in The Atlantic)

Homes inundated by lava (Source: hoto/Valdís Óskarsdóttir/Reykjavik Museum of Photography, here).

In an attempt to save as much of the town as possible and, most crucially, the town's natural harbour, volunteers constructed diversionary walls to direct the lava away from the town. Water was also pumped onto the lava flow to cool it and stop its progress.

Seawater being hosed onto the molten lava flow (source: Jónasson 1973, from USGS).

Lava flow cooled before entering the port area (source: Williamson 1973, from USGS).

Overall, the eruption covered the island in ash and added 2.5 km² (approxinately 20%) to its land area (see map below). Following its ending, people started to move home back to the island, although for some, they had lost their family homes. Today, many relics and photographs are available at the Eldheimar museum on the island and it is well worth a visit.

Monitoring today is more robust and comprehensive than it ever was in the early 1970s. The Icelandic Met Office is responsible for monitoring the country's volcanic and seismic activity and indeed, proved itself to be capable of this task given the well publicised enhancement in activity in the Reykjanes Peninsula over a year prior to the current events at Fagradalsfjall commencing in March 2021. No one knows how long the eruption at Fagradalsfjall will last but tourists certainly are making most of the unique sight (below). If Fagradalsfjall is anything like that of Eldfell then we may be coming to the end of its eruptive period however, scientists monitoring the landform are noting the same volumes of magma arriving at the site as effusing from it, suggesting we may well be in for a much longer spectical to behold. In 1210, an eruption in the same location, called the Reykjanes fires, lasted until 1240 ...!!!