Eldfell
| Eldfell | ||
|---|---|---|
 Helgafell (left) and Eldfell (right) today. The volcanic fissure of the eruption is clearly visible south of the Eldfell. |
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| height | 200 m | |
| location | Off the south coast of Iceland | |
| Coordinates | 63 ° 25 '50 " N , 20 ° 14' 47" W | |
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| Type | Cinder cone , crevice volcano | |
| rock | basalt | |
| Last eruption | 1973 (active) | |
 The lava flow four months after it was prevented from flowing (July 23, 1973 photo) |
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The Eldfell ([ ˈɛltfɛtl̥ ], Icelandic fire mountain ) is a volcano with a 200 m high cinder cone on the 13.4 km² Icelandic island of Heimaey . It formed without warning during volcanic eruptions a few hundred meters outside the city of Heimaey on January 23, 1973. Since the end of the eruptions in July 1973, the volcano has been in a state of rest.
overview
The eruptions caused a crisis for the then approx. 5,000 inhabitants and almost led to their permanent evacuation from the island.
Volcanic ash fell on Heimaey and destroyed many houses in the process. Lava flows threatened to separate the natural harbor from the sea. This would have severely affected the islanders' main source of income, fishing . Using large amounts of seawater, however, the lava was successfully cooled to the point that it came to a standstill and not only could the port continue to be used, but the 40 m high lava walls even protected it extremely well against the notorious winter storms from the east and south-east.
After the end of the eruptions, the slowly cooling lava flows were used to generate energy and hot water . The fallen pyroclastics were used to expand the airport and reclaim land , making space for 200 new houses.
Settlement
The Vestmannaeyjar (Icelandic Westman Islands ) were first settled in 874, originally possibly by fleeing Irish slaves belonging to the Nordic settlers on Iceland. These settlers gave their name ( Westmen ) to the island according to a theory , since Ireland lies west of Scandinavia.
Although there is a lack of fresh water on Heimaey and the settlers have been harassed by piracy, the island has become an important center of Icelandic fishing, as the waters are rich in fish. In addition, around the middle of the 20th century, it finally succeeded in expanding its own port, which could also accommodate motor ships and trawlers. From then on, the establishment of its own fishing industry was successfully promoted.
Geological situation
Because of its location over the Mid-Atlantic Ridge , where the Eurasian and North American plates move apart, Iceland is a region of high volcanic activity. The location of Iceland over a hotspot named after the country, which is now widely accepted by scientists, contributes significantly to the number and intensity of the outbreaks.
The Vestmannaeyjar archipelago is located off the south coast of Iceland and consists of several islands formed in the Holocene . The Vestmannaeyjar volcanic system is the youngest and most southerly of Iceland's eastern volcanic zone and has been active since the Ice Age.
Heimaey, the largest island in the group and the only one inhabited, also contains material from the Pleistocene . Before the eruption of the Eldfell, the Helgafell , a 200 m high and about 6,000 year old volcanic cone, was the most famous volcano on the island.
Modern eruptions
Since the settlement, the first major eruptions occurred in 1637 and 1896 as submarine events. Another eruption occurred in 1963 when the new island of Surtsey formed about 20 km southwest .
Scientists suspect that the increased volcanic activity is due to an expansion of the rift zone crossing Iceland to the south.
Eruption 1973
Beginning of the eruptions
On January 21, 1973, a series of weak earthquakes began around Heimaey at around 8 p.m. At first they were too weak to be noticed by the residents, but could be recorded by a seismograph 60 km away . Between 01:00 and 03:00 the following night (January 22nd) it recorded over 100 quakes. Then the number of quakes decreased again and stopped completely by 11:00. It was not until late in the evening of that day, at 11 p.m., that the earthquakes started again. Although only seven quakes were measured by 1:34 the following day, they were stronger than the previous ones; the strongest achieved a value of 2.7 on the Richter scale .
Such quakes are not uncommon at the edges of lithospheric plates , and so there was nothing to indicate an impending volcanic eruption. The eruptions therefore started practically unexpectedly. At about 1:55 a.m. on January 23, a crevice opened on the east side of the island, only about 1 km from the center of Heimaey and only 200 m east of the nearest courtyard, Kirkjubær (Icelandic churchyard), where one of the island's churches is located found.
The crevice quickly enlarged to a length of 2 km. Undersea activities were also registered, just off the north and south coasts. During the first hours, spectacular lava fountains could be observed along the fissure - a maximum of 3 km long - but the activity then concentrated on an opening about 800 m north of the Helgafell volcano and just outside the city.
During the first few days of the eruptions, an estimated 100 cubic meters of lava and pyroclastics were ejected per second . Within two days, the lava fountains had raised a volcanic cone with a height of 100 m. Originally this new volcano was called Kirkjufell (Kirchenberg) because of its proximity to the former church. However, this name was not adopted by the Icelandic authorities; they gave the volcano the name Eldfell ('fire mountain') against the resistance of the local population .
Evacuations
In the first hours of the eruptions, the Icelandic civil protection authority implemented emergency plans drawn up in advance and the entire population of the island was evacuated. The evacuation was necessary because lava flows were already beginning to flow into the east end of the city, and the entire island was threatened by falling ash .
Fortunately, due to severe storms in the preceding days, almost the entire fishing fleet was in the port, which enabled a quick evacuation. The population was alerted by the fire brigade by means of sirens and gathered in the harbor. The first boats left the island towards Þorlákshöfn at 02:30, only half an hour after the eruption began.
Most of the population left Heimaey by ship. Fortunately, lava and ash did not threaten the airfield at the beginning, so some people could also be flown out. This mainly affected elderly residents and the patients at the local hospital who could not be transported by ship. Almost all 5,300 residents were safely relocated to the main Icelandic island within six hours. Only a few people stayed behind for important work or for rescuing valuables in threatened houses.
Effects of the eruption: destruction of houses, creation of land
Houses close to the crevice were soon destroyed by lava or pyroclastics. A few days after the eruption began, the main wind direction turned west, carrying most of the ash onto the island and town. Many houses were destroyed by the weight of the falling ashes, and some were saved by volunteers. Until the end of January, pyroclastics covered large parts of the island, in some places up to 5 m high. Some houses were also set on fire by lava bombs or came under advancing lava flows.
At the beginning of February, the precipitation of pyroclastics slowly subsided, but lava flows continued to cause destruction. Submarine activity north of the island destroyed both the power cable and aqueduct that served Heimaey from the main island.
Lava also threatened to spill the port entrance. This would have been a catastrophe for the Icelandic economy, as the fishing industry is Iceland's main source of income and Heimaey is the country's main port with around 25% of Iceland's fishing.
In addition to the destruction of houses in the city, the lava also created over two square kilometers of new land in the northeast of the island. The lava flows consisted of thick, crusty ʻAʻā lava and covered the area around the volcano with an average 40 m thick lava layer, in some places up to 100 m high. As the eruptions continued, the lava flows destroyed one fish processing factory and seriously damaged two others, as well as destroying the island's power station.
Despite the outbreaks occurring so close to the city, only one death was reported. A man died after inhaling toxic fumes while trying to get something from a basement. Carbon dioxide , combined with a low concentration of toxic gases, accumulated in many buildings covered by volcanic ash. Several other people were injured breathing these gases while trying to enter contaminated homes.
Efforts have been made to evacuate the city's toxic gases. For this purpose, trenches were dug and walls were built up so that the gases, which are heavier than air, can flow out of the city or prevent them from reaching them in the first place. It was assumed that the gases came from the volcanic fissure. In retrospect, it was found that at least some of the gases underground from the volcano could have penetrated them through the old rock below the city.
Cooling the lava
The worst threat to the city was the lava flows; they threatened to separate the harbor from the sea. It has already been discussed to dig a new port entrance through a spit in the north of the island if the old one should actually be closed, but efforts have also been made to prevent it from getting that far. Attempts had already been made to use water to cool lava flows in, for example, Hawaii and Mount Etna, and in this way to stop them. These attempts made little profit, however, and they had always been small bets. Nonetheless, Prof. Þorbjörn Sigurgeirsson from Háskóli Íslands , an Icelandic university in Reykjavík , suggested spraying the lava flows with an enormous amount of seawater and thus preventing them from penetrating further into the city and the port.
The first such attempts were made on February 7th. Although only about 100 liters of water per second was pumped onto the lava, the advance slowed noticeably. The lava cooled only very slowly, but the method turned out to be very efficient, as practically all of the water used evaporated and thus extracted the heat energy from the lava. Encouraged by the first successes, efforts were rapidly increased.
At the beginning of March, a larger piece of the crater broke off and flowed in the lava flow towards the harbor. This boulder called Flakkarinn ( The Wanderer ) posed a great threat to the port if it had reached it. Attempts were made from the Sandey dredger to cool the lava flow and bring it to a standstill. The Flakkarinn finally broke into two parts, each of which remained 100 m from the port.
The subsequent attempts to cool the lava were the largest such operation in history. Up to 400 liters of water per second were sprayed onto the lava from the Sandey . In addition, a network of water pipes was placed directly on the lava in order to distribute the sea water over the largest possible area directly on the lava. Wooden reinforcements for the pipes soon caught fire from the heat, and aluminum parts of the pipe system also began to melt. The pipes themselves survived the enormous heat thanks to the cooling by the sea water. This method soon allowed an area of 1.2 hectares to be cooled. Some areas were cooled particularly intensively and thus formed natural barriers, which were further strengthened by the flowing lava that was also cooled again.
The work of placing water pipes on a lava flow that had solidified on the surface, but was still very hot and, thanks to the liquid lava inside, was still pushing forward several meters per day, was extremely dangerous. In addition, the evaporating water made visibility difficult and thus further hindered the work. With bulldozers provisional way on the lava were created, but quickly became uneven and moved several meters per day. The line layers, who called themselves Das Suicide Squad, were able to lay lines up to 130 m from the solid ground over the lava, directly onto the still moving lava flow. Several workers were burned, but none were seriously injured.
At the end of March, a fifth of the city was covered by lava. 32 pumps with a capacity of 1000 liters per second each were delivered from the USA , which finally ended the further advance of the lava flows. These pumps were actually designed to pump oil and therefore had to be retrofitted with spare parts specially developed in Reykjavík.
With the sea water, a large amount of sea salt was also applied to the lava, so that a salt crust soon formed on the solidifying rock. Estimates indicate that up to 220,000 tons of salt were deposited on land in this way.
The eruptions had made headlines around the world, and in Iceland in particular, it was widely reported. In Europe , too , news of what was going on in Iceland attracted attention, although it was competing for front-page positions with the peace negotiations on the Vietnam War in Paris . Attempts to cool the lava flows in particular attracted attention and found their way into publications such as National Geographic ( Volcano overwhelms an Icelandic village , 1973). The attention the volcanic eruption brought to Iceland, and Heimaey in particular, led to a surge in tourism in the aftermath of the eruptions.
The outbreak subsides
After the first few days, the supply of fresh lava decreased again. If 100 cubic meters of lava were initially ejected per second, this value sank to 60 m³ by February 8th. In the middle of March, only 10 m³ per second came to the surface. After that, this value did not drop as much: around the middle of April, 5 m³ were still emitted.
On May 26, volcanic activity was observed on the seabed between Heimaey and Iceland from a fishing boat, but this soon subsided. The eruptions came to a complete standstill in early July, when no more fresh lava emerged on the surface, although lava continued to flow below the surface for a few more days. Showed just before the end of the outbreaks a 1150m away from the crater Inappropriate level of, is that the floor under the crater inwardly arched, which suggested, is that the magma chamber under the volcano had emptied.
A total of 0.23 cubic kilometers of lava and 0.02 cubic kilometers of tephra were ejected during the five month eruptions. Approximately 2.5 km² of new land was added to the island, an increase of 20%. The port entrance was narrowed considerably, but remained open. In fact, the lava actually improved the harbor as the new solidified lava now serves as an additional breakwater .
Heimaey after the outbreaks
Due to the poor thermal conductivity of the solidified lava, the temperature inside the lava flows is still several hundred degrees Celsius even years after the eruption. Soon after the eruption ended, geologists began looking for ways to harness this energy source. Appropriate heating systems were soon developed, and as early as 1974 the first house was connected to this energy source. Little by little, other houses were supplied with heating energy. From 1979 four power plants were built to use the lava energy. Each of these power plants extracted the thermal energy from an area of 100 by 100 meters by pumping cold water into the rock and utilizing the returning steam. Up to 40 megawatts of power could be generated, which was enough to supply practically all houses on the island.
The vast numbers of pyroclastics were used to enlarge the runway at the island's airport, and they were also used to create new land in the sea on which 200 new houses could be built. By mid-1974 about half of the population had returned to the island, and by March 1975 it was already 80%. The restoration of the infrastructure on Heimaey was financed through a dedicated Iceland-wide sales tax , with international aid amounting to 2.1 million US dollars being made available, mainly from the former motherland Denmark , but also from the USA and several international organizations. The old hustle and bustle soon returned to the harbor, which was better protected by the new breakwater, and it remained the country's most important fishing center.
Eldfell today and in the future
At the end of the eruptions, the height of the Eldfell was about 220 m above sea level. Since then, the height has decreased by about 18 to 20 m, which is due to both erosion from the wind and rain and the compaction of the material. Grass was planted at the foot of the volcano to slow down further erosion. In the future, the entire Eldfell should be covered with grass as much as possible, as is the case with the nearby Helgafell.
The typical behavior of a volcano in the Vestmannaeyjar Archipelago is a single phase of volcanic activity. This makes further Eldfell eruptions very unlikely, but not impossible, long after the initial active phase.
Pompeii of the north
Pompeii of the North is a project that has set itself the goal of excavating part - about 7 to 10 houses - of the almost 400 buried buildings. The name alludes to the excavations in Pompeii , where houses buried by the volcano Vesuvius were exposed.
The uncovered buildings are then to be made accessible to the public as a museum in order to give a realistic impression of the events. Since the project was founded in summer 2005, three residential buildings on the buried street Suðurvegur have already been uncovered (as of 2006).
literature
- Þorleifur Einarsson (1974), The Heimaey Eruption in Words and Pictures , Heimskringla, Reykjavík
- Kristjansson L., Simon I., Cohen ML, Björnsson S. (1975), Ground tilt measurements during the 1973 Heimaey eruption , Journal of Geophysical Research, v. 80, pp. 2951-2954
- Lava-Cooling Operations During the 1973 Eruption of Eldfell Volcano, Heimaey, Vestmannaeyjar, Iceland , US Geological Survey Open-File Report 97-724
- Williams Jr.R.S., Moore J.G. (1983), Man Against Volcano: The Eruption on Heimaey, Vestmannaeyjar, Iceland , 2nd edition, published by the US Geological Survey ( PDF )
- John McPhee, The Control of Nature (1989), ISBN 0-374-12890-1 The middle third of this book is devoted to the Eldfell eruption and its consequences.
- Mattsson H., Hoskuldsson A. (2003), Geology of the Heimaey volcanic center, south Iceland: early evolution of a central volcano in a propagating rift? , Journal of Volcanology and Geothermal Research, v. 127, pp. 55-71
Web links
- Eldfell in the Global Volcanism Program of the Smithsonian Institution (English)
- VolcanoWorld information (English)
- Information from eyjar.is (English)
- A report on the eruptions and the evacuation (English)
Individual evidence
- ^ Guðjón Eyjólfsson: Vestmannaeyjar. Ferðafélag Íslands, árbók 2009, p. 165
- ↑ cf. z. B. Guðjón Eyjólfsson: Vestmannaeyjar. Ferðafélag Íslands, árbók 2009, p. 125 ff.
- ↑ cf. z. B. Eldfell in the Smithsonian Institution's Global Volcanism Program , accessed February 13, 2011
- ^ Guðjón Eyjólfsson: Vestmannaeyjar. Ferðafélag Íslands, árbók 2009, p. 169 f.
- ^ R. Williams, J. Moore: Man Against Volcano: The Eruption on Heimaey, Vestmannaeyjar, Iceland , 1976, p. 12
- ↑ Worlds of Fire: Eldheimar ( Memento of October 4, 2006 in the Internet Archive ) (Pompeii of the North), accessed: February 20, 2011
