On January 23rd 1973 a new volcano unexpectedly erupted in the Vestmannaeyjar archipelago, southwest of Iceland. The new volcano was a fissure 1.25 miles long and only 1100 yards from the center of town, also named Vestmannaeyjar. The new volcano was named Heimaey. The town was mostly evacuated over the next few days and the lava slowly flowed towards town and the mouth of the harbor for the next seven months. Vestmannaeyjar is the only good harbour in that part of Iceland, and was the base for a large fishing fleet that produces a significant part of Iceland’s GNP. As the lava threatened to overrun the town and close off the harbor, a decision was made to try to slow and divert the lava by cooling it with sea water. The idea was initially scoffed at, but when small initial efforts seemed to have an effect the scale of the operation was increased. Over seven months eight million cubic yards of sea water were pumped onto the lava flow; they cooled 5 million cubic yards of basalt lava to solid rock. The harbor and much of the town survived the eruption, likely as a result of the efforts to cool the lava.
http://volcano.und.nodak.edu/vwdocs/volc_images/europe_west_asia/heimaey/heimaey.html