The Eruption
http://volcano.und.nodak.edu/vwdocs/volc_images/europe_west_asia/heimaey/heimaey.html
Iceland is known for its volcanic activity. A few years before Heimaey erupted; a nearby sub oceanic eruption formed the new island of Surtsey. The town of Vestmannaeyjar already had an extinct volcano on its outskirts, the volcano was known as Helgafell. It was thought to have been extinct for several hundred years. In January 1973 a new fissure opened up a few hundred yards from the extinct volcano. It went clear across the island and into the ocean on both sides. Boats escaping the harbor saw red magma under the water, and sub oceanic power and water lines from the mainland were broken by the eruption. In the initial eruption a curtain of lava 500 feet erupted from the fissure, after a few days the eruption was mostly from a single vent, with a cinder cone 300 feet tall. The lava flows from the eruption were a viscous slow moving basaltic magma. Average speeds for the lava flows were 3 to 9 yards a day. These relatively slow speeds are what made it possible to try and cool and divert the lava.
http://notendur.centrum.is/~edda/heimaey1.html