On the morning of Tuesday 23rd January, 1973, at 1.55.a.m., an   eruption began from a 1600-metre fissure on the eastern side of Heimaey in   the Vestmann Islands. The eruption came without warning and was totally   unexpected.
A few mild shocks had been felt from 10 p.m. that night, the sharpest of them   occurring at 1.40 a.m. On Monday night, 22nd January, people in Heimaey   went to bed at the usual time, as on a normal weekday.

All the boats were in harbour, for during the day there had been a   south-  easterly gale, force 12, with rainfall. Just before 2 a.m. there was
  a telephone call to the police station in the town centre . Information was   received that an eruption had started a short distance above and east of   Kirkjubær," the church farm" at the easternmost end of the town.

The police officers on duty immediately drove to the area, where they found   the fissure east of Kirkjubær had now opened all the way to the sea to the   north, and southwards east of Helgafell, as far as they could see.

The whole length of the fissure was erupting, with a row of lava fountains so   close to one another that it was like an unbroken wall of fire. The eruption   began in what is now the main crater of the new volcano, later known as   Eldfell.
From the beginning lava ran down the slope from the fissure east and   north-  east, and at once started to form a lava salient out to sea. Soon the   fire alarm was sounded, while fire and police cars patrolled the streets with   sirens going in order to wake people.

Within about two hours most of the population was afoot. People then began   to stream down to the harbour, having just had time to put on the most   necessary warm clothing and gather together a few belongings. Thanks to   the gale of the previous day there were between 60-70 boats in the   harbour.

Both island boars and others that had taken shelter there were now hurriedly   prepared for departure, and the fist left for Þorlákshöfn at 2.30 a.m.   followed by a steady stream. For reasons of safety the town council   decided that night to evacuate the whole population, apart from those   employed on essential work.

There was a danger of the harbour approaches being sealed off, should the   fissure extend any further northwards, while the airfield might be closed,   too, if it extended southwards. Contact was also made with Icelandair, the   smaller airways companies in Reykjavík, and the NATO Defence Force in   Keflavík.

Aircraft from all these landed on Heimaey, for it was good flying weather,   and during the night 300 people, mostly the sick and aged, were   transported to Reykjavík by air. Some time after 4 a.m. the State Radio   began to broadcast announcements and news reports on the eruption. Thus   it may be reckoned that about 5,000 people were evacuated from Heimaey   on the first night of the eruption, most of them by boat.

The whole operation went remarkably smoothly and without mishap, thanks   above all the favourable weather that night, but also to the calmness of the   people in faxe of the calamity that had overwhelmed them. By the morning   of Tuesday 23rd January the most urgent rescue operations had therefore   been completed and the islanders escaped unscathed from the greatest peril   that had ever threatened the population of an urban area in Iceland.
  Between two and three hundred stayed behind to carry out essential duties.

It is estimated that approximately 250 million cubic metres of lava and   ash were produced by the eruption,about 10% of which were ash and   pumice. The volcano had reached a height of around 225 metres by the end   of the eruption.
Heimaey had previously been some 12 square kilometres, but had extended   to 14,5 square kilometres after the eruption. About 5,5 million tons of   seawater containing some 180 thousand tons of salt were pumped onto the   lava flow in an attempt to cool it.
Some 360 houses were destroyed on Heimaey, about 30% of the town’s   house, and some 400 were damaged, while 400 houses escaped nearly   unscathed. About 1,5 million tons of ash fell on the town, approximately one   thousand tons covered the hospital’s roof alone.
By 1975, most of the ash had been cleaned away and moved to the new lava   field, where it was used to make roads, enlarge air strips and make   foundations for new houses. About two-thirds of the islanders cane back   after the eruption about 3500 out of 5300 pre-eruption residents. The total   population is now about 5000.