Eldfell is a volcano that sits in the fishing port of Vestmannaeyjar, on the island of Heimaey, about ten kilometers south of the Icelandic mainland. Vestmannaeyjar is the only inhabited site in this area. On January 23, 1973, Eldfell erupted, and subsequently destroyed more than 30% of the town. Interestingly enough, the damage might have been even more devastating, had the town and government of Iceland not acted quickly to employ methods to stop the lava flow. One of those methods of mitigation was the spraying of sea water directly onto the flow. It proved significantly effective, and has been the subject of much study since that time, particularly by the United States, to determine whether this same method might prove successful in mitigating lava flows in Hawaii (Williams & Moore, 1983).
Lava flows in Iceland differ greatly depending on their viscosity, total output, speed of formation and surrounding terrain (USGS, 2001). Viscosity is a substance’s internal friction and resistance to flow (Abbott, 2009), and it is a lava flow’s viscosity that ultimately determines the flow’s movement. Because viscosity increases as the lava cools, the goal in the mitigation of a lava flow is to increase its viscosity. By doing this, the flow can be slowed to allow evacuation and minimization of property loss, diverted to less populated areas, or even better yet, stopped completely to avoid further losses. Because water absorbs heat from lava, it is an effective means of slowing or controlling lava flows (USGS, 2001).
For the 1973 Heimaey eruption, the first attempts to cool the lava with water were begun about two weeks after the eruption, with the goal being to protect both the town and the harbor. Firemen from the city’s fire department began by using fire hoses and an unsophisticated network of pumps, which were provided by the Icelandic mainland, as well as the international community. Ã’ It was easy to see that this method did cool the lava, but that it would not be enough to save the town. The lava began to pile up, reaching about 20 meters high, and subsequently became unstable. The pumping equipment in use was not powerful enough to get the water to the top of the crest, and due to the intense temperatures of the lava, hoses could not be placed on the flow itself (USGS, 2001).
On March 1, the dredging boat, Sandey, arrived in Vestmannaeyjar, and was given the task of preventing the advancing flow from reaching the harbor. Part of Sandey’s cargo was an inventory of 22 inch diameter steel pipes that were laboriously bolted together to form a pipeline of about 200 meters. By now the lava tongue was about 30 meters high and it is estimated that the newly improvised pipeline allowed the Sandey to spray about 400,000 metric tons of sea water onto it. Fortunately, that was enough to cool the tongue, and prevent its further spread in that direction (USGS, 2001).
Meanwhile, however, lava continued to flow in other areas, and it became apparent that additional and more powerful equipment was going to be necessary to stop it. An assessment was completed on March 11 which estimated that in order to completely stop the flow, equipment would be needed that could pump twice as much water than what the Sandey had been able to pump (which was only about 400 l/s-1), as well as deliver that water three times as high (to a height of about 90 meters). It was further estimated, that if the town and harbor were to be saved, said equipment would have to arrive within one week. Over two weeks later, on March 26, more powerful pumping equipment finally arrived from the United States, but took an additional five to six days to install (USGS, 2001). When all was said and done, about one-third of the town had been destroyed by the lava (Williams & Moore, 1983).
The mitigation efforts employed on Heimaey illustrate that the spraying of sea water on lava flows is, indeed, an effective method of slowing, diverting, or stopping the flow. This is significant for any areas where hazards from lava flows lie near a large water source such as our oceans. It is also a good case study for mitigation planning, providing valuable data concerning the type of equipment needed and the timing to which mitigation efforts need to begin.
In the case of the Eldfell eruption, sea water spraying was started on a small scale, and gradually increased as learnings accumulated and more and better equipment became available.Ã’ Valuable time was lost in this process however, as a total time lapse of nine and a half weeks passed from the initial eruption to the time all the necessary equipment was in place to stop the flow. Now, however, given the sum of the learnings accumulated over the course of the entire event, it may be possible to dramatically reduce the non-beneficial goods and services provided by any future lava flows, in Iceland or around the world.
Abbott, P.L. (2009). Natural disasters (7th ed.). New York, NY: McGraw-Hill Companies, Inc.
USGS. (2001). Lava cooling. Retrieved July 18, 2009, from http://pubs.usgs.gov/of/1997/of97-724/lavacool.html
USGS. (2001). Lava cooling on Heimaey ‘” methods and procedures. Retrieved July 18, 2009, from http://pubs.usgs.gov/of/1997/of97-724/methods.html
Williams, R. S. & Moore, J. G. (1983). Man against volcano: The eruption on Heimaey, Vestmannaeyjar, Iceland. Retrieved July 18, 2009, from http://126.96.36.199/search?q=cache:oRZlZs92rQoJ:pubs.usgs.gov/gip/