How it began
In January 1967 Thorbjorn Sigurgeirsson, a physics professor at the University of Iceland, sprayed water on a lava flow advancing into a lagoon on the new island of Surtsey and found that the front could be made to solidify early. When the Eldfell eruption began on Heimaey on January 23, 1973, and lava threatened to close the harbor of the town of Vestmannaeyjar, he became a strong proponent of spraying seawater on the flow fronts. The first spraying began on February 6 or 7, 1973, and the operation ran until July 10, 1973.
Before it existed
Earlier efforts to protect property from lava relied on barriers or explosives. The US Army Air Corps bombed lava flows from Mauna Loa in Hawaii in 1935 and 1942, with results considered inconclusive because the flows stopped at about the same time. Dikes and diversion barriers had been tried or planned in Italy, Japan, Samoa and Hawaii. A US Geological Survey review calls the Heimaey cooling the most extensive such operation ever attempted.
How it works
Seawater sprayed on the flow front turned almost entirely to steam and took heat with it, so the lava surface changed from reddish and blocky to jagged and black to grey. The chilled lava formed internal barriers, and the flow behind thickened and piled up on itself instead of moving forward. Crews laid a network of pipes on top of the lava, up to 130 meters back from the front, to spread water over as much as 12,000 square meters at once. Wooden and aluminum supports melted in the hottest spots, but the pipes survived because cold seawater ran through them.
What changed first
The first attempt delivered 100 liters per second. On March 1 the dredging ship Sandey was brought in and sprayed up to 400 liters per second on a moving block of crater wall called Flakkarinn. In late March, 32 pumps with a capacity of up to 1,000 liters per second each arrived from the United States. About 7.3 million cubic meters of seawater had been pumped by the end. The lava stopped about 100 meters short of blocking the harbor entrance, and the cost was put at 1,447,742 US dollars.
What lasted
The new lava field narrowed the harbor entrance but worked as a breakwater that improved its shelter, and the fishery returned to normal production by 1974. Knowledge from the cooling work was applied directly to a district heating system that drew heat from the cooling lava. Experiments began in 1974, the design was approved in late 1979, and by 1983 a 5 megawatt heat-exchanger plant was sending hot water to more than half the buildings in town. The reports were later translated by the US Geological Survey for use in other volcanic regions.
