Iceland stands on the mid-Atlantic volcanic ridge and is constantly experiencing eruptions. The 1973 one was one of the most destructive in the country’s history.
One of the most destructive volcanic eruptions in the history of Iceland began in the early morning of January 23, 1973, near the town of Vestmannaeyjar, Iceland’s main fishing port. It is located on the Island of Heimaey, the only inhabited island in the archipelago of the Vestmann Islands on Iceland’s south coast. The strength of the eruption was 3 on the VEI scale, about one-tenth that of Mount Pelee in 1902, but its destructive power was enormous, obliterating one-third of the town of Vestmannaeyjar.
It might have been much more destructive were it not for the unique corrective approach taken by the islanders. They sprayed the advancing flows of lava with large volumes of seawater. The result was that the lava flows were slowed down or stopped and on occasion diverted from the undamaged portion of the town.
Iceland is one of the most active volcanic regions in the world, with eruptions occurring on average every five years. This one was the fifth eruption within a decade. About a third of all the basaltic lavas erupted in recorded history have been produced by Icelandic eruptions. Iceland’s location astride the Mid-Atlantic Ridge, where the Eurasian and North American tectonic plates are moving apart, is partly responsible for this intense volcanic activity, but there is an additional reason for the presence of so much volcanic material above the surface of the ocean. It is because Iceland stands over a hot spot, just as Hawaii and Yellowstone National Park do.
The mid-ocean ridge where lava emerges from deep within the earth and spreads east and west across the Atlantic is an underwater mountain range extending for 82,000 miles around the earth. However, because of the larger amount of lava being erupted above a hot spot, erupted material from the mid-ocean ridge at Iceland rises high above sea level.
Thus, the state of Iceland is a volcanic island built almost completely of cooled basaltic lava and through the middle of the Island runs the midocean Atlantic ridge, a rare coincidence and a location that is ideal for studying the behavior of the ridge. The speed at which the two plates move away from each other can easily be measured on a site like this using GPS technology. The speed is less than an inch a year. Accordingly, on the east and west sides of the Island of Iceland geologists can locate rocks that are fifty million years older than those emerging from the ridge. If they examine still farther away from the ridge, say on the shore of Greenland for the North American Plate and the west coast of Scotland for the Eurasian one, they can identify rocks that are fifty million years older that the lava that is just emerging from the ridge.
Because of its close proximity to the mid-ocean ridge, Iceland has been able to capitalize on the geothermal resources that lie close at hand. In Reykjavik, the capital, all of its heating needs are met from this resource. Approximately 10 percent of all the nation’s electrical requirements also come from this same source. The government is working toward making the country completely free from the gases that harm the environment.
The eruption of Mount Eldfell began on the eastern side of the Island of Heimaey, only a thousand yards from the center of the town of Vest- mannaeyjar, and soon a fissure more than a mile long opened up. Within two days the lava and tephra cone from the eruption was over three hundred feet high. Volcanic ash and bombs were being emitted at a rate of 130 cubic yards a second. Within a few weeks the cone had doubled in height. The islanders watched as their town was being steadily destroyed, homes wiped out, buildings of all kinds collapsing, and the harbor filling in.
The international economy of Iceland was being threatened by the destruction of its key fishing port. The island’s 5,300 residents had already been evacuated to the main part of the country. One surge of lava into the eastern part of the town destroyed a large fish-freezing plant, damaged two others, and destroyed the local power-generating facility. Within two months the costs of the eruption had risen to tens of millions of dollars, this for a country that has a Gross National Product of half a billion dollars.
Several Icelandic scientists proposed spraying the lava with seawater to stop it or at least slow it down so that some of the town could be preserved. This decision proved to be the most ambitious program ever attempted to control volcanic activity and thus it became an event that attracted the attention of many other countries facing volcanic eruptions. Efforts were directed at two locations, the northwest of the town where many fish-processing factories were sited, and the entrance to the harbor.
Early on it was discovered that the water slowed the advance of lava and also made the front of the flow thicken and solidify. Pump ships were brought it to provide a greater volume of water and their combined output ensured sprays of 40 cubic feet per second. This was sufficient to cool half of the lava flow to a temperature that was below the point of solidification of basalt. The cooling of the lava flow was matched by the creation of diversion barriers of scoria beside the lava. Thus, the partly cooled lava tended to pile up against the barriers rather than burrow under them. Overall water- cooling and construction of lava barriers had a marked effect on both the character and the movement of lava. The eight million cubic yards of water converted five cubic yards of molten lava to solid rock.
Even after the devastation and disruption of lives and livelihood there were some peripheral benefits. The lava and tephra added a square mile to the area of Heimaey. Over a million cubic yards of tephra were cleared away from the town and used to extend the runways on the island’s only airfield and to provide landfill for the construction of two hundred new homes. The worldwide interest in what happened in Heimaey meant that Mount Eldfell became one of the most photographed volcanic eruptions in the world.