Eldfell
Encyclopedia
Eldfell is a composite volcanic cone
just over 200 metres (656.2 ft) high on the Iceland
ic island of Heimaey
. It formed in a volcanic eruption which began without warning just outside the town of Heimaey on 23 January 1973. Its name means Mountain of Fire 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 around 400 homes, 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.
After the eruption finished, the islanders used heat from the slowly cooling lava flows to provide hot water and to generate electricity
. They also used some of the extensive tephra
, fall-out of airborne volcanic material, to extend the runway at the island's small airport, and as landfill
, on which 200 new houses were built.
, where the North American
and Eurasian Plate
s are moving apart, and also over the Iceland hotspot
, which greatly enhances the volcanic activity. It is estimated that a third of all the basalt
ic 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 ft) 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 (12.4 mi) 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 largest tremor 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 ft) east of Kirkjubær (Church farm), where the island's church had once been located.
The fissure rapidly extended from 300 metres to a length of 2 kilometres (1.2 mi), 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 fountain
ing 50 to 150 metres high occurred along the whole fissure, which reached a maximum length of about 3 kilometres (1.9 mi) during the first few hours of the eruption, but activity soon became concentrated on one vent, about 0.8 kilometre (0.497098189319845 mi) 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 ft) 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. The fountains’ Strombolian eruptions continued until 19 February, depositing thick tephra over the northern half of the island and adding to the cone until it was 200 metres (660 ft) high.
The eruption column that caused the air fall “occasionally rose to 9,000 metres (30,000 ft), or nearly to the tropopause
”. Lava flows from the cone traveled north and east to produce a “continuously expanding lava delta
” along the east coast of the island and into the harbor, where small explosions built up a diminutive island that was soon overtaken by the advancing delta.
"the viscosity
of the lava fragments ejected by the blasts was, for basalt, relatively high. Very little spatter was produced and scoria
bombs sometimes broke up explosively in flight (presumably due to rapid vesiculation
), and by rapid impact on landing." The high viscosity led to a "massive, blocky aā lava flow which moved slowly but relentlessly toward the north, northeast, and east."
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. Planes were sent from Reykjavik
and Keflavik
to help speed the process. 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. Cattle, horses and sheep on the island were slaughtered.
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 kilometre (0.77220431718507 sq mi) to the island, and into the eastern parts of town, destroying several hundred houses. The flows were thick and blocky aā lava (Icelandic: apalhraun) flows, and covered the ground to average depths of about 40 metre (130 ft), reaching 100 metre (330 ft) 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 CO2 (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 CO2 originated deep within the volcanic conduit and percolated through older volcanic rocks, rising directly into the town.
and on Mount Etna
, but these had been rather small-scale operations with limited success. However, Páll Zóphóníasson calculated that it should be relatively easy to solidify the lava flows by spraying them with more copious 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 litre
s per second (26 US (liquid) gallon
s 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 Þorbjörn 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 ft) 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 12,000 square metres (3 acre
s) 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.
The work involved in laying pipes over an active lava flow 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-talkie
s 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 ft) 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 tonne
s (240,000 short ton
s) of salt was deposited in total.
Sigurgeirsson called these protective measures “undoubtedly the most extensive that have ever been used in a volcanic eruption” and said that “had it not been for the cooling, the lava tongue [into the harbor] could be expected to…extend further along its direction of movement…for a whole month longer than it actually did. It failed by only about 100 meters to block the entrance to the harbor.”
The entire operation cost a total of US$1,447,742 at the time.
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.
The attention focused on the island as a result of the eruption led to a later upsurge in tourism
once the eruption was over.
Short-lived submarine activity was discovered by a fishing vessel on 26 May, about 4 kilometres (2.5 mi) north-east of Heimaey and 1 kilometre (0.621372736649807 mi) 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 ft) 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 kilometre (0.965255396481338 sq mi) 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, 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.
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 ft) 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.
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, as over a third of Iceland's total fish catch is from this harbour.
By the end of the eruption, Eldfell stood about 220 metres (720 ft) 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 gravel
ly 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.
Volcanic cone
Volcanic cones are among the simplest volcanic formations. They are built by ejecta from a volcanic vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, depending upon the nature and size of the fragments ejected during the eruption...
just over 200 metres (656.2 ft) high on the Iceland
Iceland
Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...
ic island of Heimaey
Heimaey
Heimaey , literally Home Island, is an Icelandic island. At a size of 13.4 km² , it is the largest island in the Vestmannaeyjar archipelago, and the largest and most populated Icelandic island outside the main island of Iceland. Heimaey lies approximately 4 nautical miles off the south coast...
. It formed in a volcanic eruption which began without warning just outside the town of Heimaey on 23 January 1973. Its name means Mountain of Fire in Icelandic
Icelandic language
Icelandic is a North Germanic language, the main language of Iceland. Its closest relative is Faroese.Icelandic is an Indo-European language belonging to the North Germanic or Nordic branch of the Germanic languages. Historically, it was the westernmost of the Indo-European languages prior to the...
.
The eruption caused a major crisis for the island and nearly led to its permanent evacuation
Emergency evacuation
Emergency evacuation is the immediate and rapid movement of people away from the threat or actual occurrence of a hazard. Examples range from the small scale evacuation of a building due to a bomb threat or fire to the large scale evacuation of a district because of a flood, bombardment or...
. Volcanic ash
Volcanic ash
Volcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions, less than in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact...
fell over most of the island, destroying around 400 homes, and a lava flow threatened to close off the harbour, the island's main income source via its fishing
Fishing
Fishing is the activity of trying to catch wild fish. Fish are normally caught in the wild. Techniques for catching fish include hand gathering, spearing, netting, angling and trapping....
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.
After the eruption finished, the islanders used heat from the slowly cooling lava flows to provide hot water and to generate electricity
Electricity generation
Electricity generation is the process of generating electric energy from other forms of energy.The fundamental principles of electricity generation were discovered during the 1820s and early 1830s by the British scientist Michael Faraday...
. They also used some of the extensive tephra
Tephra
200px|thumb|right|Tephra horizons in south-central [[Iceland]]. The thick and light coloured layer at center of the photo is [[rhyolitic]] tephra from [[Hekla]]....
, fall-out of airborne volcanic material, to extend the runway at the island's small airport, and as landfill
Landfill
A landfill site , is a site for the disposal of waste materials by burial and is the oldest form of waste treatment...
, on which 200 new houses were built.
Background
Iceland is a region of frequent volcanic activity, due to its location astride the Mid-Atlantic RidgeMid-Atlantic Ridge
The Mid-Atlantic Ridge is a mid-ocean ridge, a divergent tectonic plate boundary located along the floor of the Atlantic Ocean, and part of the longest mountain range in the world. It separates the Eurasian Plate and North American Plate in the North Atlantic, and the African Plate from the South...
, where the North American
North American Plate
The North American Plate is a tectonic plate covering most of North America, Greenland, Cuba, Bahamas, and parts of Siberia, Japan and Iceland. It extends eastward to the Mid-Atlantic Ridge and westward to the Chersky Range in eastern Siberia. The plate includes both continental and oceanic crust...
and Eurasian Plate
Eurasian Plate
The Eurasian Plate is a tectonic plate which includes most of the continent of Eurasia , with the notable exceptions of the Indian subcontinent, the Arabian subcontinent, and the area east of the Chersky Range in East Siberia...
s are moving apart, and also over the Iceland hotspot
Iceland hotspot
The Iceland hotspot is a hotspot which is partly responsible for the high volcanic activity which has formed the island of Iceland.-Description:...
, which greatly enhances the volcanic activity. It is estimated that a third of all the basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
ic lava erupted in the world in recorded history has been produced by Icelandic eruptions.
The Vestmannaeyjar (Icelandic
Icelandic language
Icelandic is a North Germanic language, the main language of Iceland. Its closest relative is Faroese.Icelandic is an Indo-European language belonging to the North Germanic or Nordic branch of the Germanic languages. Historically, it was the westernmost of the Indo-European languages prior to the...
for Westman islands) archipelago
Archipelago
An archipelago , sometimes called an island group, is a chain or cluster of islands. The word archipelago is derived from the Greek ἄρχι- – arkhi- and πέλαγος – pélagos through the Italian arcipelago...
lies off the south coast of Iceland, and consists of several small islands, all formed by eruptions in the Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...
epoch. Heimaey, the largest island in the group and the only inhabited one, also contains some material from the Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
era. The most prominent feature on Heimaey before 1973 was Helgafell
Helgafell (volcano)
Helgafell is an inactive 227 metre high volcanic cone located on the island of Heimaey in the Vestmannaeyjar archipelago in Iceland.The Stórhöfði peninsula immediately to the south of Helgafell in what is now southern Heimaey formed about 6000 years ago, with Helgafell forming from a secondary...
, a 200 metre (650 ft) 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
Irish people
The Irish people are an ethnic group who originate in Ireland, an island in northwestern Europe. Ireland has been populated for around 9,000 years , with the Irish people's earliest ancestors recorded having legends of being descended from groups such as the Nemedians, Fomorians, Fir Bolg, Tuatha...
slaves belonging to Norse
Viking
The term Viking is customarily used to refer to the Norse explorers, warriors, merchants, and pirates who raided, traded, explored and settled in wide areas of Europe, Asia and the North Atlantic islands from the late 8th to the mid-11th century.These Norsemen used their famed longships to...
settlers on the mainland. These settlers gave the islands their name, Ireland being west of mainland Scandinavia
Scandinavia
Scandinavia is a cultural, historical and ethno-linguistic region in northern Europe that includes the three kingdoms of Denmark, Norway and Sweden, characterized by their common ethno-cultural heritage and language. Modern Norway and Sweden proper are situated on the Scandinavian Peninsula,...
. Although plagued by poor water supplies and piracy
Piracy
Piracy is an act of robbery or criminal violence at sea. The term can include acts committed on land, in the air, or in other major bodies of water or on a shore. It does not normally include crimes committed against persons traveling on the same vessel as the perpetrator...
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
Surtsey
Surtsey is a volcanic island off the southern coast of Iceland. At it is also the southernmost point of Iceland. It was formed in a volcanic eruption which began 130 metres below sea level, and reached the surface on 15 November 1963. The eruption lasted until 5 June 1967, when the island...
, was formed by a four-year eruption which began offshore about 20 kilometres (12.4 mi) 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 (37.3 mi) away, near the mainland, recorded over 100 large tremors between 01:00 and 03:00 on 22 January that appeared to be emanating from south of Heimaey. 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 that grew shallower and more intense, while the epicenter moved closer to the town of Vestmannaeyjar.The largest tremor measured 2.7 on the Richter scale
Richter magnitude scale
The expression Richter magnitude scale refers to a number of ways to assign a single number to quantify the energy contained in an earthquake....
.
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 ft) east of Kirkjubær (Church farm), where the island's church had once been located.
The fissure rapidly extended from 300 metres to a length of 2 kilometres (1.2 mi), 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 fountain
Lava fountain
A lava fountain is a volcanic phenomenon in which lava is forcefully but non-explosively ejected from a crater, vent, or fissure. Lava fountains may reach heights of up to . They may occur as a series of short pulses, or a continuous jet of lava. They are commonly seen in Hawaiian eruptions.-See...
ing 50 to 150 metres high occurred along the whole fissure, which reached a maximum length of about 3 kilometres (1.9 mi) during the first few hours of the eruption, but activity soon became concentrated on one vent, about 0.8 kilometre (0.497098189319845 mi) 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
Tephra
200px|thumb|right|Tephra horizons in south-central [[Iceland]]. The thick and light coloured layer at center of the photo is [[rhyolitic]] tephra from [[Hekla]]....
emission from the fissure was estimated to be 100 cubic metres per second
Second
The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock....
(3,500 cubic feet per second), and within two days, the lava fountains had built a cinder cone
Cinder cone
According to the , Cinder Cone is the proper name of 1 cinder cone in Canada and 7 cinder cones in the United States:In Canada: Cinder Cone In the United States:...
over 100 metres (330 ft) 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. The fountains’ Strombolian eruptions continued until 19 February, depositing thick tephra over the northern half of the island and adding to the cone until it was 200 metres (660 ft) high.
The eruption column that caused the air fall “occasionally rose to 9,000 metres (30,000 ft), or nearly to the tropopause
Tropopause
The tropopause is the atmospheric boundary between the troposphere and the stratosphere.-Definition:Going upward from the surface, it is the point where air ceases to cool with height, and becomes almost completely dry...
”. Lava flows from the cone traveled north and east to produce a “continuously expanding lava delta
Lava delta
Lava deltas form wherever sub-aerial flows of lava enter standing bodies of water. The lava cools and breaks up as it encounters the water, with the resulting fragments filling in the seabed topography such that the sub-aerial flow can move further offshore...
” along the east coast of the island and into the harbor, where small explosions built up a diminutive island that was soon overtaken by the advancing delta.
"the viscosity
Viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...
of the lava fragments ejected by the blasts was, for basalt, relatively high. Very little spatter was produced and scoria
Scoria
Scoria is a volcanic rock containing many holes or vesicles. It is most generally dark in color , and basaltic or andesitic in composition. Scoria is relatively low in mass as a result of its numerous macroscopic ellipsoidal vesicles, but in contrast to pumice, all scoria has a specific gravity...
bombs sometimes broke up explosively in flight (presumably due to rapid vesiculation
Vesicular texture
Vesicular texture is a volcanic rock texture characterised by a rock being pitted with many cavities at its surface and inside. The texture is often found in extrusive aphanitic, or glassy, igneous rock...
), and by rapid impact on landing." The high viscosity led to a "massive, blocky aā lava flow which moved slowly but relentlessly toward the north, northeast, and east."
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 ashVolcanic ash
Volcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions, less than in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact...
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
Þorlákshöfn
Þorlákshöfn is a town on the southern coast of Iceland in the Municipality called Ölfus.The town name is named after Þorláki Helga who was bishop at Skálholt...
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
Tephra
200px|thumb|right|Tephra horizons in south-central [[Iceland]]. The thick and light coloured layer at center of the photo is [[rhyolitic]] tephra from [[Hekla]]....
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. Planes were sent from Reykjavik
Reykjavík
Reykjavík is the capital and largest city in Iceland.Its latitude at 64°08' N makes it the world's northernmost capital of a sovereign state. It is located in southwestern Iceland, on the southern shore of Faxaflói Bay...
and Keflavik
Keflavík
Keflavík is a town in the Reykjanes region in southwest Iceland. In 2009 its population was of 8,169.In 1995 it merged with Njarðvík and Hafnir to form a municipality called Reykjanesbær with a population of 13,971 .- History :...
to help speed the process. 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. Cattle, horses and sheep on the island were slaughtered.
Destruction of houses, creation of land
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 ft) 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 kilometre (0.77220431718507 sq mi) to the island, and into the eastern parts of town, destroying several hundred houses. The flows were thick and blocky aā lava (Icelandic: apalhraun) flows, and covered the ground to average depths of about 40 metre (130 ft), reaching 100 metre (330 ft) 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 CO2 (carbon dioxide)
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
. 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 CO2 originated deep within the volcanic conduit and percolated through older volcanic rocks, rising directly into the town.
Lava-cooling operations
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 HawaiiHawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...
and on Mount Etna
Mount Etna
Mount Etna is an active stratovolcano on the east coast of Sicily, close to Messina and Catania. It is the tallest active volcano in Europe, currently standing high, though this varies with summit eruptions; the mountain is 21 m higher than it was in 1981.. It is the highest mountain in...
, but these had been rather small-scale operations with limited success. However, Páll Zóphóníasson calculated that it should be relatively easy to solidify the lava flows by spraying them with more copious 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 litre
Litre
pic|200px|right|thumb|One litre is equivalent to this cubeEach side is 10 cm1 litre water = 1 kilogram water The litre is a metric system unit of volume equal to 1 cubic decimetre , to 1,000 cubic centimetres , and to 1/1,000 cubic metre...
s per second (26 US (liquid) gallon
Gallon
The gallon is a measure of volume. Historically it has had many different definitions, but there are three definitions in current use: the imperial gallon which is used in the United Kingdom and semi-officially within Canada, the United States liquid gallon and the lesser used United States dry...
s 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
Steam
Steam is the technical term for water vapor, the gaseous phase of water, which is formed when water boils. In common language it is often used to refer to the visible mist of water droplets formed as this water vapor condenses in the presence of cooler air...
. 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 Þorbjörn 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 ft) 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
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
supports melted, but the pipes themselves were prevented from melting by the cold seawater flowing through them. Up to 12,000 square metres (3 acre
Acre
The acre is a unit of area in a number of different systems, including the imperial and U.S. customary systems. The most commonly used acres today are the international acre and, in the United States, the survey acre. The most common use of the acre is to measure tracts of land.The acre is related...
s) 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.
The work involved in laying pipes over an active lava flow 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-talkie
Walkie-talkie
A walkie-talkie is a hand-held, portable, two-way radio transceiver. Its development during the Second World War has been variously credited to Donald L. Hings, radio engineer Alfred J. Gross, and engineering teams at Motorola...
s 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 ft) 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
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. 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
Reykjavík
Reykjavík is the capital and largest city in Iceland.Its latitude at 64°08' N makes it the world's northernmost capital of a sovereign state. It is located in southwestern Iceland, on the southern shore of Faxaflói Bay...
and brought in.
One notable feature of the lava cooling operation was the deposit of large amounts of salt
Salt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...
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 tonne
Tonne
The tonne, known as the metric ton in the US , often put pleonastically as "metric tonne" to avoid confusion with ton, is a metric system unit of mass equal to 1000 kilograms. The tonne is not an International System of Units unit, but is accepted for use with the SI...
s (240,000 short ton
Short ton
The short ton is a unit of mass equal to . In the United States it is often called simply ton without distinguishing it from the metric ton or the long ton ; rather, the other two are specifically noted. There are, however, some U.S...
s) of salt was deposited in total.
Sigurgeirsson called these protective measures “undoubtedly the most extensive that have ever been used in a volcanic eruption” and said that “had it not been for the cooling, the lava tongue [into the harbor] could be expected to…extend further along its direction of movement…for a whole month longer than it actually did. It failed by only about 100 meters to block the entrance to the harbor.”
The entire operation cost a total of US$1,447,742 at the time.
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
Vietnam War
The Vietnam War was a Cold War-era military conflict that occurred in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. This war followed the First Indochina War and was fought between North Vietnam, supported by its communist allies, and the government of...
peace talks in Paris
Paris
Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...
. The efforts of the islanders to halt the lava flows received particular attention, with coverage in publications such as National Geographic.
The attention focused on the island as a result of the eruption led to a later upsurge in tourism
Tourism
Tourism is travel for recreational, leisure or business purposes. The World Tourism Organization defines tourists as people "traveling to and staying in places outside their usual environment for not more than one consecutive year for leisure, business and other purposes".Tourism has become a...
once the eruption was over.
The eruption dies down
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 mi) north-east of Heimaey and 1 kilometre (0.621372736649807 mi) 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
Tiltmeter
A tiltmeter is an instrument designed to measure very small changes from the horizontal level, either on the ground or in structures. A similar term, in less common usage, is the inclinometer...
1150 metres (3750 ft) from the crater which had been measuring ground deformation throughout the eruption detected subsidence towards the crater, implying that the shallow magma chamber
Magma chamber
A magma chamber is a large underground pool of molten rock found beneath the surface of the Earth. The molten rock in such a chamber is under great pressure, and given enough time, that pressure can gradually fracture the rock around it creating outlets for the magma...
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 kilometre (0.965255396481338 sq mi) 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, 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 insides of lava flows can remain at temperatures of several hundred degrees for many years due to the very low thermal conductivityThermal conductivity
In physics, thermal conductivity, k, is the property of a material's ability to conduct heat. It appears primarily in Fourier's Law for heat conduction....
of rock. Following the end of the eruption, scientists began to assess the feasibility of extracting geothermal
Geothermal heating
Geothermal heating is the direct use of geothermal energy for heating applications. Humans have taken advantage of geothermal heat this way since the Paleolithic era. Approximately seventy countries made direct use of a total of 270 PJ of geothermal heating in 2004...
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 ft) 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.
The abundant tephra produced by the eruption was used to extend the runways at the island's small airport, and also as landfill
Land reclamation
Land reclamation, usually known as reclamation, is the process to create new land from sea or riverbeds. The land reclaimed is known as reclamation ground or landfill.- Habitation :...
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
Hypothecation
Hypothecation is the practice where a borrower pledges collateral to secure a debt. The borrower retains ownership of the collateral, but it is "hypothetically" controlled by the creditor in that he has the right to seize possession if the borrower defaults...
sales tax
Sales tax
A sales tax is a tax, usually paid by the consumer at the point of purchase, itemized separately from the base price, for certain goods and services. The tax amount is usually calculated by applying a percentage rate to the taxable price of a sale....
, as well as through international aid totalling US$ 2.1 million primarily from Denmark
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. 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, as over a third of Iceland's total fish catch is from this harbour.
By the end of the eruption, Eldfell stood about 220 metres (720 ft) 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 gravel
Gravel
Gravel is composed of unconsolidated rock fragments that have a general particle size range and include size classes from granule- to boulder-sized fragments. Gravel can be sub-categorized into granule and cobble...
ly tephra
Tephra
200px|thumb|right|Tephra horizons in south-central [[Iceland]]. The thick and light coloured layer at center of the photo is [[rhyolitic]] tephra from [[Hekla]]....
as well as wind erosion
Erosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...
. The islanders have planted grass
Grass
Grasses, or more technically graminoids, are monocotyledonous, usually herbaceous plants with narrow leaves growing from the base. They include the "true grasses", of the Poaceae family, as well as the sedges and the rushes . The true grasses include cereals, bamboo and the grasses of lawns ...
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.
See also
- Geography of IcelandGeography of IcelandIceland is a medium-sized island in the North Atlantic ocean. The island is located east of Greenland and immediately south of the Arctic Circle, atop the divergent boundary of the Mid-Atlantic Ridge in the North Atlantic Ocean. It lies about from New York City and from Scotland...
- Lakes of Iceland
- List of volcanoes in Iceland
- Volcanism in Iceland
Further reading
- Bertmarks förlag, K.G., Aktuellt 1973 (1973) ISSN 0343-6993, p. 97-104
- Center for Short-Lived Phenomena Event Reports 1545, 1547, 1552, 1567,
- Kristjansson L., Simon I., Cohen M.L., Björnsson S. (1975), Ground tilt measurements during the 1973 Heimaey eruption, Journal of Geophysical Research, v. 80, p. 2951–2954
- Mattsson H., Hoskuldsson A. (2003), Geology of the Heimaey volcanic centre, south Iceland: early evolution of a central volcano in a propagating rift?, Journal of Volcanology and Geothermal Research, v. 127, p. 55–71
- McPhee, J.John McPheeJohn Angus McPhee is an American Pulitzer Prize-winning writer, widely considered one of the pioneers of creative nonfiction....
, The Control of Nature (1989) ISBN 0374128901. The middle third of this book is devoted to this eruption, its immediate effects, the lava-cooling operations, and the people involved and affected.