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Eldfell

2007 Schools Wikipedia Selection. Related subjects: European Geography

   Eldfell is a cinder cone volcano just over 200 metres (650 feet) high
   on the Icelandic island of Heimaey. It formed in a volcanic eruption
   which began without warning just outside the town of Heimaey on January
   23, 1973. Its name means Fire Mountain in Icelandic.

   The eruption caused a major crisis for the island and nearly led to its
   permanent evacuation. Volcanic ash fell over most of the island,
   destroying many houses, and a lava flow threatened to close off the
   harbour, the island's main income source via its fishing fleet. An
   operation was mounted to cool the advancing lava flow by pumping sea
   water onto it, which was successful in preventing the loss of the
   harbour.

   Following the end of the eruption, the islanders used the heat from the
   slowly cooling lava flows to provide hot water and to generate
   electricity. They also used some of the extensive tephra fall of
   airborne volcanic material to extend the runway at the island's small
   airport, and as landfill on which 200 new houses were built.

Background

   Heimaey before the eruption
   Enlarge
   Heimaey before the eruption

   Iceland is a region of frequent volcanic activity, due to its location
   astride the Mid-Atlantic Ridge, where the North American and Eurasian
   Plates are moving apart, and also over the Iceland hotspot, which
   greatly enhances the volcanic activity. It is estimated that a third of
   all the basaltic lava erupted in the world in recorded history has been
   produced by Icelandic eruptions.

   The Vestmannaeyjar ( Icelandic for Westman islands) archipelago lies
   off the south coast of Iceland, and consists of several small islands,
   all formed by eruptions in the Holocene epoch. Heimaey, the largest
   island in the group and the only inhabited one, also contains some
   material from the Pleistocene era. The most prominent feature on
   Heimaey before 1973 was Helgafell, a 200 metre (650 foot) high volcanic
   cone formed in an eruption about 5,000 years ago.

   The Vestmannaeyjar archipelago was settled in about 874 AD, originally
   by escaped Irish slaves belonging to Norse settlers on the mainland.
   These settlers gave the islands their name, Ireland being west of
   mainland Scandinavia. Although plagued by poor water supplies and
   piracy during much of its history, Heimaey became the most important
   centre of the Icelandic fishing industry, having one of the few good
   harbours on the southern side of the country, and being situated in
   very rich fishing grounds.

   Since the settlement, no eruptions had been known to occur on the
   islands until 1963, when a new member of the archipelago, Surtsey, was
   formed by a four year eruption which began offshore about 20 kilometres
   (12 miles) south-west of Heimaey. However, offshore eruptions may have
   taken place in 1637 and 1896. Scientists have speculated that volcanic
   activity in the archipelago may be increasing due to the southward
   propagation of the rift zone which crosses Iceland.

The eruption begins

   At about 20:00 on 21 January 1973, a series of small tremors began to
   occur around Heimaey. They were too weak to be felt by the residents of
   the island, but a seismic station 60 kilometres (35 miles) away
   recorded over 100 small tremors between 01:00 and 03:00 on 22 January.
   The tremors continued at a reduced rate until 11:00 that day, after
   which they stopped until 23:00 that evening. From 23:00 until 01:34 on
   23 January, seven tremors were detected, the largest of which measured
   2.7 on the Richter scale.

   Small tremors are very common at plate boundaries, and nothing here
   indicated that they heralded a major eruption. The onset of the
   eruption was therefore almost entirely unexpected. At about 01:55 on 23
   January, a fissure opened up on the eastern side of the island, barely
   a kilometre away from the centre of the town of Heimaey, approximately
   200 metres (650 feet) east of Kirkjubær (Church farm), where the
   island's church had once been located.

   The fissure rapidly extended to a length of 2 kilometres (1.2 miles),
   crossing the island from one shore to the other. Submarine activity
   also occurred just offshore at the northern and southern ends of the
   fissure. Spectacular lava fountaining occurred along the whole fissure,
   which reached a maximum length of about 3 kilometres (2 miles) during
   the first few hours of the eruption, but activity soon became
   concentrated on one vent, about 0.8 kilometre (0.5 mile) north of the
   old volcanic cone of Helgafell and just outside the eastern edge of the
   town.

   During the early days of the eruption, the rate of lava and tephra
   emission from the fissure was estimated to be 100 cubic metres per
   second (3,500 cubic feet per second), and within two days, the lava
   fountains had built a cinder cone over 100 metres (330 feet) high. The
   name initially given to the new volcano was Kirkjufell (Church
   Mountain), owing to its proximity to Kirkjubær. This name was not
   adopted by the official Icelandic place-naming committee, who chose
   Eldfell (Fire Mountain) instead, despite local opposition.

Evacuation

   In the early hours of the eruption, the Icelandic State Civil Defence
   Organisation evacuated the entire population of Heimaey, having
   previously developed evacuation plans for an emergency such as this.
   The evacuation was necessary because lava flows were already moving
   slowly into the eastern side of town, and the whole of the small island
   was threatened by the likelihood of heavy ash fall.

   Because of severe storms in the days before the eruption, almost the
   entire fishing fleet was in the harbour, a stroke of luck which greatly
   assisted the organisation of the rapid evacuation. The population was
   alerted to the situation by fire engines sounding their sirens, and
   gathered by the harbour with just the small amount of possessions they
   were able to carry. The first boats left for Þorlákshöfn at about
   02:30, just half an hour after the start of the eruption.

   Most of the population left the island by boat. Fortunately, the lava
   flows and tephra fall did not at first affect the island's airstrip,
   and a few people who were unable to travel by boat were evacuated by
   air—primarily the elderly and patients from the hospital. Within six
   hours of the onset of the eruption, almost all of the 5,300 people of
   the island were safely on the mainland. A few people remained to carry
   out essential functions and to salvage belongings from threatened
   houses.

Destruction of houses, creation of land

   Houses buried by ash
   Enlarge
   Houses buried by ash

   Houses close to the rift were soon destroyed by lava flows and tephra
   fall. A few days after the eruption began, the prevailing wind
   direction moved to the west, resulting in extensive tephra falls over
   the rest of the island, causing extensive property damage. Many houses
   were destroyed by the weight of the ash fall, but crews of volunteers
   working to clear the ash from roofs and board up windows saved many
   more. By the end of January, tephra covered most of the island,
   reaching 5 metres (16 feet) deep in places. Apart from falling ash,
   some houses were also burned down by fires caused by lava bombs, or
   overridden by advancing lava flows.

   By early February, the heavy tephra fall had abated, but lava flows
   began to cause serious damage. Submarine activity just north of the
   fissure severed an electric power cable and a water pipeline which
   supplied electrical power and water from the Icelandic mainland, and
   lava began to flow into the harbour, a situation which caused serious
   concerns - if the harbour was destroyed, the island's fishing industry
   would be devastated. As Heimaey was responsible for some 25% of
   Iceland's total annual catch, the effect on the whole country's economy
   would be significant. Efforts to prevent the loss of the harbour are
   described further below.

   Lava flows also moved into the sea east of the island, creating new
   land that would eventually add over 2 square kilometres (0.8 square
   mile) to the island, and into the eastern parts of town, destroying
   several hundred houses. The flows were thick and blocky aa lava
   (Icelandic:apalhraun) flows, and covered the ground to average depths
   of about 40 metre (130 feet), reaching 100 metre (330 feet) thick in
   places. Later on in the eruption, a surge of lava destroyed one fish
   processing plant and damaged two others, and also demolished the town's
   power generating plant.

   Despite the eruption's close proximity to the town and the extensive
   property damage, only one fatality could be attributed to the eruption
   - a man who had broken into a chemist's store to acquire drugs was
   suffocated by toxic fumes. Carbon dioxide, with small amounts of
   poisonous gases, became concentrated in many buildings partially buried
   by tephra, and several other people were affected when entering these
   buildings.

   Efforts to mitigate the hazards presented by the accumulation of
   poisonous gas included the building of a large tephra wall to divert
   gases away from the town, and the digging of a trench to channel away
   the CO[2] (carbon dioxide). These defences were only partially
   effective, as they relied on the assumption that the gases were
   produced at the vent, and flowed into the town from there. It is
   believed that as least some of the CO[2] originated deep within the
   volcanic conduit and percolated through older volcanic rocks, rising
   directly into the town.

Lava-cooling operations

   Steam rises copiously where seawater is being used to cool the flows
   Enlarge
   Steam rises copiously where seawater is being used to cool the flows

   The possibility of lava flows cutting off the harbour was the most
   significant threat facing the town. One contingency plan devised,
   should the harbour be closed off, was to cut through a low sand spit on
   the north side of the island to provide a new channel into the harbour,
   but it was hoped that if the lava flow could be slowed, this would not
   be necessary. Lava flows had been sprayed with water in attempts to
   slow them in Hawaii and on Mount Etna, but these had been rather
   small-scale operations with limited success. However, Professor
   Þorbjörn Sigurgeirsson of the University of Iceland calculated that it
   should be relatively easy to solidify the lava flows by spraying them
   with more copius amounts of sea water.

   The first attempt to slow the lava flow by spraying the leading edge
   with sea water began on 7 February, and although the volume of water
   being pumped on was rather small at 100 litres per second (26 US
   (liquid) gallons per second), the flow was noticeably affected. The
   water cooling of the lava was slow, but achieved a maximum efficiency,
   with almost all the water being converted to steam. Once the viability
   of lava cooling had been proven, efforts to halt the flows were
   increased.

   The pumping capacity was increased in early March, when a large chunk
   of the crater wall broke away from the summit of Eldfell and began to
   be carried along the top of the lava flow towards the harbour. The
   chunk, dubbed Flakkarinn (The Wanderer), would have seriously
   threatened the viability of the harbour if it had reached it, and the
   dredging boat Sandey was brought in on 1 March to prevent its advance.
   Professor Sigurgeirsson provided advice to the pumping crews on where
   to direct their efforts to most efficiently slow the flows. Eventually
   the Wanderer broke up into two pieces which both stopped approximately
   100 metres (330 feet) from the harbour mouth.

   The ensuing lava-cooling operations were the most ambitious that had
   ever been undertaken. The Sandey was able to spray up to 400 litres per
   second (105 US gallons per second) onto the advancing flow, and a
   network of pipes was laid on top of the lava to distribute the seawater
   over as wide an area as possible. Wooden supports for the pipes caught
   fire where the lava was hottest, and even aluminium supports melted,
   but the pipes themselves were prevented from melting by the cold
   seawater flowing through them. Up to 1.2 hectares (3 acres) of lava
   flow could be cooled at one time, with internal barriers then being
   created within the flow, which thickened and piled up upon itself.
   A lava flow nearly 4 months after it had stopped flowing into a street
   - photographed 23 July 1973
   Enlarge
   A lava flow nearly 4 months after it had stopped flowing into a street
   - photographed 23 July 1973

   The work involved in laying pipes over an active lava was highly
   dangerous, with low visibility due to the extensive emission of steam.
   Rough tracks were made onto the flow by bulldozing tephra, but these
   tracks quickly became very uneven and moved several metres a day. The
   pipelayers used bulldozers and walkie-talkies to advance through the
   steam to lay more pipes. The workers dubbed themselves 'The Suicide
   Squad', and managed to lay pipes up to 130 metres (430 feet) inward
   from the flow front, directly over the advance. Although several men
   sustained minor burns, no serious injuries were received.

   By the end of March, a fifth of the town had been covered by lava
   flows, and increased pumping capacity was required. Thirty-two pumps,
   each with a capacity of up to 1000 litres per second (265 US gallons
   per second), were brought in from the USA. After these pumps began to
   cool the flow advancing towards the town, its movement slowed
   dramatically and soon stopped. Failure of pump shafts became a problem
   after a few weeks, probably because they were designed for pumping oil
   rather than water, and new and improved shafts had to be manufactured
   in Reykjavík and brought in.

   One notable feature of the lava cooling operation was the deposit of
   large amounts of salt where seawater was sprayed onto the lava. Large
   expanses of flow became encrusted with extensive white deposits, and it
   was estimated that up to 220,000 tonnes (240,000 short tons) of salt
   was deposited in total.

   The eruption had made headlines around the world when it began, and was
   covered constantly by Icelandic news crews throughout. In Europe, the
   eruption was one of the biggest news items while it continued,
   competing for front page space with breakthroughs then being made in
   the Vietnam War peace talks in Paris. The efforts of the islanders to
   halt the lava flows received particular attention, with coverage in
   publications such as National Geographic (e.g. Volcano overwhelms an
   Icelandic village, 1973). The attention focused on the island as a
   result of the eruption led to a later upsurge in tourism once the
   eruption was over .

The eruption dies down

   Sketch showing the changes to Heimaey caused by the eruption of Eldfell
   Enlarge
   Sketch showing the changes to Heimaey caused by the eruption of Eldfell

   The volume of lava being emitted during the eruption fell steadily
   after the first few days. From its initial rate of 100 cubic metres per
   second (3500 cubic feet per second), the emission rate fell to about 60
   cubic metres per second (2100 cubic feet per second) by 8 February, and
   just 10 cubic metres per second (350 cubic feet per second) by the
   middle of March. The decline was slower after that, but by the middle
   of April the flow rate had fallen to about 5 cubic metres per second
   (180 cubic feet per second).

   Short-lived submarine activity was discovered by a fishing vessel on 26
   May, about 4 kilometres (2.5 miles) north-east of Heimaey and 1
   kilometre (0.6 mile) off the coast of the mainland. The eruption
   finally came to an end in early July, when flowing lava was no longer
   visible, although subsurface flows may have continued for a few days
   longer. Shortly before the end of the eruption, a tiltmeter 1150 metres
   (3750 feet) from the crater which had been measuring ground deformation
   throughout the eruption detected subsidence towards the crater,
   implying that the shallow magma chamber which had fed the eruption was
   emptying out.

   In total, the volume of lava and tephra emitted during the five-month
   eruption was estimated to be about 0.25 cubic kilometre (0.06 cubic
   mile). About 2.5 square kilometres (1 square mile) of new land was
   added to the island, increasing its pre-eruption area by some 20%. In
   the end, the harbour entrance was narrowed considerably but not closed
   off, and the new lava flow acted as a breakwater, actually improving
   the shelter afforded by the harbour. Flakkarinn rafted several hundred
   metres towards the harbour along the top of the lava flow, but came to
   a halt well away from the water's edge.

Heimaey since the eruption

   The street shown above, cleared of lava after the eruption
   Enlarge
   The street shown above, cleared of lava after the eruption

   The insides of lava flows can remain at temperatures of several hundred
   degrees for many years due to the very low thermal conductivity of
   rock. Following the end of the eruption, scientists began to assess the
   feasibility of extracting geothermal heat from the gradually cooling
   flows. Experimental heating systems were soon devised, and by 1974 the
   first house was connected. The scheme was extended to several more
   houses and the hospital, and in 1979 construction began of four larger
   plants to extract heat from the flows. Each plant extracted energy from
   a square 100 metres (330 feet) on each side, by percolating water down
   into the hot parts and collecting the resulting steam. Up to 40
   megawatts (MW) of power could be generated by the plants, which also
   then supplied hot water to nearly every house on the island.
   Helgafell (left) and Eldfell (right) today. The line of the 1973
   fissure south of Eldfell is clearly seen
   Enlarge
   Helgafell (left) and Eldfell (right) today. The line of the 1973
   fissure south of Eldfell is clearly seen

   The abundant tephra produced by the eruption was used to extend the
   runways at the island's small airport, and also as landfill on which
   200 new homes were built. By mid-1974, about half the pre-eruption
   population had returned to the island, and by March 1975, about 80% had
   returned. The recovery and reconstruction of Heimaey was paid for by
   all Icelanders via a hypothecated sales tax, as well as through
   international aid totalling US$ 2.1 million primarily from Denmark but
   with substantial contributions from the United States and several
   international organisations. With the harbour improved by the new lava
   breakwater, the fishing industry regained its former vigour and the
   island today remains the most important fishing centre in the nation.

   By the end of the eruption, Eldfell stood about 220 metres (720 feet)
   above sea level. Since then, its height has dropped by 18 to 20 metres
   (60 to 65 feet), due to slumping and compacting of the unconsolidated
   gravelly tephra as well as wind erosion. The islanders have planted
   grass around the lower slopes of the otherwise bare hill, to stabilise
   it against further erosion, and eventually it is expected that most of
   the volcano will be covered by grass, as neighbouring Helgafell is.
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