With Hawaii's Kilauea erupting, here's how one Icelandic town fought a volcano and won

While residents of Hawaii's Big Island stand by helplessly watching hot lava flows destroy their homes and property, they may find comfort in knowing how a town in Iceland fought back against a volcano in 1973 and saved their harbour.

About 200 kilometres southeast of the main island of Iceland is the small volcanic island of Heimaey and its main town, Vestmannaeyjar, one of the premier fishing ports in the country. The community depends on a well-protected harbour, which gets its protection from a narrow entrance that was formed by previous lava flows from volcanic eruptions.

In January 1973, long fissures appeared on the flanks of Helgafell, a volcano above the town. Lava fountains, similar to those seen in Hawaii rose out of the fissures, followed by thick clouds of black volcanic ash that built a new cinder cone called Eldfell. A change in wind pattern blew the ash over the town, prompting an evacuation of the residents and the loss of more than 200 buildings as the ash piled up to a depth of five metres.

Icelanders are used to living with volcanic eruptions because the entire archipelago is part of the Mid-Atlantic Ridge, a huge crack in the crust of the Earth that is constantly spreading apart, bringing new material up from the interior of the Earth. Iceland itself is a part of this underwater mountain chain that sticks above the ocean, and indeed, the island is splitting apart, which is why it is so volcanically active.

Undaunted, the townspeople of Vestmannaeyjar returned to dig out from under the ash, saving much of their town, but by the end of February 1973, lava began to flow towards the north east threatening to block off the harbour, which would destroy the town's only source of income.

Geologists monitoring the eruption suggested spraying seawater onto the leading edge of the lava with the idea of cooling and solidifying it, thereby creating a dam that would divert the flow away from the harbour. They began a small spraying operation using city water and the fire department, but soon realized that was woefully inadequate to fight molten rock at over 1,000 C.

With a call for international help, ships arrived from the United States with pumping equipment and more than 30 kilometres of pipe that were laid out across the land to spray seawater over the lava. This was the largest attempt by humans to fight a volcano in history and of great interest to scientists and engineers who might be able to apply the same technique to future eruptions.

For seven months water was sprayed over the lava, producing a cooling effect that caused it to become more viscous, slowing its flow. Bulldozers built up dams along the cooling fronts to divert the flow and by the end of that July the eruption subsided and the harbour was saved. Not only did this herculean effort preserve a way of life, the town later built a geothermal plant beside the new lava flow to tap into the deep heat of the rock providing low cost heat to most of the buildings.

Vestmannaeyjar had a lot going for it in this battle against nature. The value of the harbour was so high it was in the national interest to provide funds to protect it. Large ships could bring equipment right into into the town, good roads provided access to the lava flow, and seawater was readily available.

Whether the same effort could be made to divert the flows in Hawaii is an open question. True, the lava flows are slow and viscous on the big island, but the community being threatened is purely residential, which is a tragedy for the people who live there, but the main ports of Hilo and Kona are not affected by the eruption. It might be easier and cheaper to relocate and rebuild rather than mount a monumental effort to fight the lava.

The other important factor to consider is that the eruption in Iceland eventually stopped, ending the battle. Had it continued for an extended period, the effort might not have been so successful. Hawaiian eruptions are known to continue for years.

Volcanoes are among the most powerful and destructive forces in nature. Usually, they are unstoppable, but in at least one case, humans fought back and won.