Europe's largest glacier covers ten percent of the North Atlantic country of Iceland. It also covers not one but two or more powerful volcanoes. This country is no stranger to volcanic eruptions, as by some estimates the nation experiences one eruption every three years. In fact, most of the citizens of Iceland do not give much notice to any volcano that may lie close to their home, or the periodic rumblings from the ground. But, in 1996, when a volcano once thought to be dormant began to show signs of a definate life and volitile nature, the entire country took notice. This volcano not only was located under the Vatnajokull glacier, but it was angry and ready to erupt.
For the school year of 1996-1997, I was a resident alien of the country of Iceland. For the year between high school and college, I decided to be an exchange student to this country located on the Mid-Atlantic Ridge. I experienced earthquakes, a small-scale avalanche, a "red" Christmas, geysers, hot springs, and the great eruption and subsequent jokulhlaup. As a result of this experience, I gained first-hand knowledge of the basic geology of Iceland, as well as a short history of previous eruptions and happenings. My experience during the eruption under the ice is not overly dramatic or even interesting, as I was living on the other side of the island at the time. I did, however, travel to Vatnajokull, after the jokulhlaup was over, to see the icebergs stranded on the shore, the damage caused by the water, and the source of the floodwaters located inside an ice cavern. The pictures I took at those times are not yet on the site, but the links below will take you to pages with similar (or better) pictures, and some figures showing the flooded area, the subglacial lake location, and numerical data.
Jokulhlaup is one of the few Icelandic words that does not translate directly into English. It does, however, mean almost the same thing as "flood." Just to satisfy any non-Icelandic-speaking audience members, "jokulhlaup" means "the flood coming from a glacier, almost always after a volcanic eruption has melted a significant portion of the ice." Now that some vocabulary has been established, I will try to relay a short, yet accurate play-by-play of the eruption and flooding.
Vatnajokull covers almost 8,100 square kilometers, and is almost one-half of a kilometer thick. Late in the evening of September 30, 1996, seismometers detected the beginning of an eruption under the glacier. One of the volcanoes had previously collapsed and formed a caldera named Grimsvotn, in which a subglacial lake had been accumulated. Late on the first of October, the day after the eruption started, the surface of the ice over the caldera had risen ten to fifteen meters. The next day, the eruption broke through the surface of the ice, emitting an ash cloud ten kilometers high. The volcano quieted on the thirteenth, but the ice continued to melt and overflow the Grimsvotn lake. More than three cubic kilometers of ice melted, but little was emitted through normal runoff points. Since an ice dam and the caldera itself held the melt back, the jokulhlaup would not occur until November, or at least one month later.
At 7:20am on the fifth of November, the meltwater burst vertically from two kilometers above the tongue of the glacier. By four that afternoon, the jokulhlaup was fully realized. A mixture of sediment, meltwater, and ice moved at ten kilometers per hour from the full twenty-kilometer width of the glacier's terminus across Skeidararsandur, forming standing waves three and four meters high. The total flow peaked at over fifty thousand cubic meters per second in the five outwash channels, making it briefly the second largest river of the world. The flood obliterated a 376-meter-long bridge, the majority of a second bridge nine hundred meters in length, twelve kilometers of roadway, twenty-three power-line towers, and causing fourteen million United States dollars in damage while adding seven square kilometers to the area of Iceland. Thankfully, there were no fatalities or injuries, and the flood did not reach any nearby settlements.
Clery, D. (1997, June 27). Monitoring a killer volcano through clouds and ice. Science (Online source).
Volcano erupting under glacier threatens Iceland. (1996, Oct. 04). Agence France Presse, (Online Source).
Fire and Ice. (1996, October 19). Economist, p. 85.
Gawlock, J. (1996, November 06). Meltdown: great flood begins as the biggest glacier goes liquid. The Independent (London), p. 7.
Monterasky, L. (1996, November 23). Volcanoes under ice: Recipe for a flood. Science News, p. 327.
Schoonmaker, D. (1998, September). Science observer: Jokulhlaup. American Scientist, pp. 426-427.
Soderlind, R. (1996, November 7). Volcanic eruption comes hot on heels of Icelandic glacier flood. The Herald (Glasgow), p. 12.
You can also access the links below for more information about the actual eruption. The above articles were found on GALILEO in the University of Georgia library.
Links to Pictures and other Info
A collection of images from the eruption and flood
Figures of the eruption site
Pics of The subglacial lagoon
http://www.hi.is/~mmh/gos/photos3.html
Jokullhlaup pics - the aftermath
