81-462: Hecla is the traditional English spelling of the Icelandic volcano, Hekla , and may also refer to: Places [ edit ] Fury and Hecla Strait , Nunavut, Canada Hecla, Kentucky , USA Hecla, Missouri , USA Hecla, Montana , USA Hecla Iron Works Building , Brooklyn, NY, USA Hecla, South Dakota , USA Hecla, Wyoming , USA,
162-436: A flow rate of around 1500 m³/s. For the first two hours, tephra was produced at the rate of 10000 m³/s. The cloud from the eruption, which had reached 53,000 feet (16,154 m) by 10:10 pm, caused a lightning storm . The tephra was transported northwards by the wind, causing the sky to turn black in places – 190 km (120 mi) away at Blönduós tephra fell from midnight until 2 am, and ash fell on
243-460: A trawler 330 km (210 mi) away at 2 am. Icelanders sampled the tephra fall in their locality by putting a plate outside to capture everything that fell onto it. This, and other measurements, showed the area covered was long and narrow with the 1 mm contour (an equivalent of 8 tonnes per hectare) extending to the north coast. By 5:30 on 6 May, the lava flow measured 4 km (2.5 mi) long. Many lava bombs were found near
324-407: A 2–4 cm layer of tephra was deposited over Austur-Húnavatnssýsla and Skagafjördur, resulting in the deaths of both fish and livestock. Rangárvellir, Land and Hreppar also suffered damage. During the eruption up to 0.5 m (1 ft 8 in) lava bombs were thrown 15–20 km (9.3–12.4 mi) away, and flooding was caused by the sudden melting of snow and ice on Hekla's slopes. Hekla
405-462: A 900 m (3,000 ft) long fissure opened 1 m (11 sq ft)1 km north of the main Hlídargígar crater. That night it contained 17 lava fountains, each 20–50 m (66–164 ft) in height. By the evening of the next day, 10–12 craters had formed, each throwing pieces of lava 50–100 m (160–330 ft) in the air. This row of craters was named Öldugígar. Gradually
486-463: A VEI of 3 and produced 0.2 km (0.048 cu mi) of lava covering an area of 18.5 km (7.1 sq mi) and 6.6×10 m³ of tephra, deposited over an area of 40,000 km (15,000 sq mi), mainly to the northwest of the volcano. The main Hekla fissure only erupted at its far southwest end, most of the eruption was from other fissures nearby. The eruption stopped in
567-454: A century after the last eruption of Hekla proper, the longest dormant period since 1104. Before the eruption the volcano had been visible from the surrounding area but nothing remarkable was noticed. The eruption occurred at 6:41 am ± 3 min with a loud roar; later eruptions could be heard throughout Iceland. An earthquake at 6:50 am measured 6 on the Mercalli intensity scale and increased
648-499: A century later. It started on 25 July and was particularly violent (VEI 4), firing volcanic bombs as far as Vördufell , 40 km (25 mi) west. Tephra was deposited over Rangárvellir , Holt and Landeyjar , 0.2 km (0.048 cu mi) in total. A man in Landsveit was killed. A VEI-4 eruption began on 3 January and lasted for over 6 months, with 0.15 km (0.036 cu mi) of tephra being deposited to
729-471: A couple of hours or less. Some are very short (a week to ten days) whereas others can stretch into months and years (the 1947 eruption started 29 March 1947 and ended April 1948). But there is a general correlation: the longer Hekla goes dormant, the larger and more catastrophic its opening eruption will be. The most recent eruption was on 26 February 2000. One of the largest Holocene eruptions in Iceland
810-509: A crater at 780 m (2,560 ft) was producing a lava column which reached an altitude of around 1 km (0.62 mi). During the night a 700 m (2,300 ft) high lava fountain was thrown up from the main crater. A 500 m (1,600 ft) long fissure starting below the Lava Crater opened, and lava fountains and other lava flows emanated from it. One hour into the eruption, a new 400 m (1,300 ft) fissure opened to
891-458: A decade. The dates were recently recalibrated of the major eruptions and a table is given below as the difference in dates could cause confusion. Unless otherwise stated eruption dates in Year (2019 values) column are from Global Volcanism Program and Catalogue of Icelandic Volcanoes, As other sources can disagree, there has been a recent literature update. The values and range given in
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#1732765319208972-566: A fluorine content of 0.2%, and two days after the eruption contaminated grass had a dry weight content of up to 0.4% fluorine. 450 farms and 95,000 sheep were affected by the eruption. Some sheep were kept inside and fed on hay or moved, but other farmers were forced to graze their flocks outside. Tephra Tephra is fragmental material produced by a volcanic eruption regardless of composition, fragment size, or emplacement mechanism. Volcanologists also refer to airborne fragments as pyroclasts . Once clasts have fallen to
1053-672: A ghost town near Laramie Hecla and Fury Islands , Nunavut, Canada Hecla and Griper Bay , Nunavut and Northwest Territories, Canada Hecla-Grindstone Provincial Park , Manitoba, Canada Hecla (South Uist) , a 606 m mountain on the island of South Uist, Scotland Ships [ edit ] Hecla -class bomb vessel Hecla -class survey vessel HMS Hecla , various RMS Hecla , Cunard Line ocean liner Other uses [ edit ] Hecla Mining , Idaho based mining company Calumet and Hecla Mining Company , Michigan, USA Calumet & Hecla Band See also [ edit ] Hekla Topics referred to by
1134-498: A great eruption of the mountain. On the night of 1 September, the dwellers in its neighbourhood were terrified by a fearful underground groaning, which continued till mid-day on the 2nd. Then, with a tremendous crash, there were formed in the sides of the cone two large openings, whence there gushed torrents of lava, which flowed down two gorges on the flanks of the mountain. The whole summit was enveloped in clouds of vapour and volcanic dust. The neighbouring rivers became so hot as to kill
1215-579: A series of craters, two of which are generally the most active. Hekla has a morphological type between that of a fissure vent and stratovolcano (built from mixed lava and tephra eruptions) sited at a rift- transform junction in the area where the south Iceland seismic zone and eastern volcanic zone meet. The unusual form of Hekla is found on very few volcanoes around the world, notably Callaqui in Chile . The 5.5 km (3.4 mi) Heklugjá fissure opens along its entire length during major eruptions and
1296-659: A single buoyant jet of magma from the Earth's core instead of cracks in the ocean floor. This is reflected in the decreasing age of the islands east to west from Fuerteventura to El Hierro. There are about 60 volcanoes in Ethiopia, located in east Africa. In Southern Ethiopia, the Omo Kibish Rock Formation is composed of layers of tephra and sediment. Within these layers, several fossils have been discovered. In 1967, 2 Homo sapiens fossils were discovered in
1377-526: A single eruption—to create a chronological framework in which paleoenvironmental or archaeological records can be placed. Often, when a volcano explodes, biological organisms are killed and their remains are buried within the tephra layer. These fossils are later dated by scientists to determine the age of the fossil and its place within the geologic record. Tephra is any sized or composition pyroclastic material produced by an explosive volcanic eruption and precise geological definitions exist. It consists of
1458-560: A variety of materials, typically glassy particles formed by the cooling of droplets of magma , which may be vesicular, solid or flake-like, and a varying proportions of crystalline and mineral components originating from the mountain and the walls of the vent. As the particles fall to the ground, they are sorted to a certain extent by the wind and gravitational forces and form layers of unconsolidated material. The particles are further moved by ground surface or submarine water flow. The distribution of tephra following an eruption usually involves
1539-484: Is a religious site for locals. It last erupted in 1903. In 2017, new fossil evidence was discovered that determined the date of Paektu Mountain's first eruption, which had been a mystery. A team of scientists directed by Dr. Clive Oppenheimer, British volcanologist , discovered a larch trunk embedded within Paektu Mountain. After radiocarbon dating, the larch was determined to be 264 years old which coincides with
1620-570: Is closely studied today for parameters such as strain , tilt, deformation and other movement and seismic activity. Earthquakes in the volcano's vicinity are generally below magnitude 2 while it is dormant and magnitude 3 when erupting. The earliest recorded eruption of Hekla took place in 1104. Since then there have been between twenty and thirty considerable eruptions, with the mountain sometimes remaining active for periods of six years with little pause. Eruptions in Hekla are varied and difficult to predict. Precursor seismic activity may only be for
1701-399: Is different from Wikidata All article disambiguation pages All disambiguation pages Hekla Hekla ( Icelandic pronunciation: [ˈhɛhkla] ), or Hecla , is an active stratovolcano in the south of Iceland with a height of 1,491 m (4,892 ft). Hekla is one of Iceland's most active volcanoes ; over 20 eruptions have occurred in and around
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#17327653192081782-440: Is fed by a magma reservoir estimated to have a top 4 km (2.5 mi) below the surface with centroid 2.5 km (1.6 mi) lower. The chamber extends to an unusual depth of more than 10 km (6.2 mi), and the more silicic lavas have matured at more than 9 km (5.6 mi). Many of the eruptions commence with thicker more explosive rhyolite , dacite or andesite eruptives which create tephra and have
1863-521: Is likely that this was both the second greatest lava eruption of Hekla whilst Iceland was inhabited and the second greatest lava eruption in the world in the period 1900–1970. A total lava volume 0.8 km (0.19 cu mi) was produced with 0.21 km (0.050 cu mi) of tephra. The height of Hekla was 1,447 m (4,747 ft) before the eruption, increasing to a maximum of 1,503 m (4,931 ft), before dropping to 1,491 m (4,892 ft) subsequently. The eruption occurred over
1944-623: Is likely to be the source of the Efrahvolshraun lava on Hekla's west. The VEI-3 eruption began on 4 December. The VEI-2 eruption and the 1206 eruption distributed around 0.24 km (0.058 cu mi) of tephra mainly to the northeast. This VEI-4 eruption, which started on 11 July and lasted for a year, was the second largest tephra eruption of Hekla since Iceland was settled, covering 30,000 km (12,000 sq mi) of land with 0.31 km (0.074 cu mi) of tephra. Over 0.5 km (0.12 cu mi) of lava
2025-466: Is over forty thousand years old and has erupted 11 times since 1800. In South America , there are several historic active volcanoes. In southern Chile , the Chaitén volcano erupted in 2011 adding 160 meters to its rim. Prehistoric weapons and tools, formed from obsidian tephra blocks, were dated at 5,610 years ago and were discovered 400 km away. Due to the location of the subduction zone of
2106-431: Is the only Icelandic volcano to produce calc-alkaline lavas. Phenocrysts in Hekla's lava can contain plagioclase , pyroxene , titanomagnetite , olivine , and apatite . When not erupting Hekla is often covered with snow and small glaciers ; it is also unusually aseismic with activity only starting 30–80 minutes before an eruption. Hekla is located on the mid-ocean ridge, a diverging plate boundary . Hekla
2187-581: Is used in broad context within an account by Aristotle of an eruption on Vulcano (Hiera) in Meteorologica . The release of tephra into the troposphere affects the environment physically and chemically. Physically, volcanic blocks damage local flora and human settlements. Ash damages communication and electrical systems, coats forests and plant life, reducing photosynthesis , and pollutes groundwater . Tephra changes below- and above-ground air and water movement. Chemically, tephra release can affect
2268-533: The Canary Islands . The most recent El Hierro eruption occurred underwater, in 2011, and caused earthquakes and landslides throughout the Canary Islands. Instead of ash, floating rocks, 'restingolites' were released after every eruption. After the 2011 eruption, fossils of single-celled marine organisms were found in the restingolites verifying the origin theory that Canary Island growth comes from
2349-507: The Omo Kibish Formation by Richard Leaky , a paleoanthropologist. After radiocarbon dating, they were determined to be 195 thousand years old. Other mammals discovered in the formation include Hylochoerus meinertzhageni (forest hog) and Cephalophus (antelope). In Asia, several volcanic eruptions are still influencing local cultures today. In North Korea, Paektu Mountain , a stratovolcano, first erupted in 946 AD and
2430-704: The Roman culture. Also, in Italy, Stromboli volcano , a stratovolcano, last erupted in July 2019. Several volcanic eruptions have been studied in North America . On 18 May 1980, Mount St. Helens , a stratovolcano in Washington state , erupted, spreading five hundred million tons of tephra ash across Washington, Oregon, Montana and Idaho causing earthquakes , rockslides , and megatsunami which severely altered
2511-554: The last ice age . During the last 7,000 years, one third of the volcanic ash deposited in Scandinavia, Germany, Ireland, and the United Kingdom originated from Hekla. Hekla had been dormant for at least 250 years when it erupted explosively in 1104 (probably in the autumn), covering 55,000 km (21,000 sq mi) which is over half of Iceland with 1.2 km / 2.5 km of rhyodacitic tephra. This
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2592-527: The water cycle . Tephra particles can cause ice crystals to grow in clouds, which increases precipitation . Nearby watersheds and the ocean can experience elevated mineral levels, especially iron , which can cause explosive population growth in plankton communities. This, in turn, can result in eutrophication . In addition to tephrochronology, tephra is used by a variety of scientific disciplines including geology , paleoecology , anthropology , and paleontology , to date fossils, identify dates within
2673-549: The ʻAʻā lava type with Pāhoehoe and lava a budella (lava tubes) areas. In April and May 1948 CO 2 emitted from cracks in the ground pooled in hollows near to Hekla, killing 15 sheep and some wild animals and birds. In total 24,000 tonnes (26,000 tons) of CO 2 was emitted. Ditches were dug by farmers to drain these hollows, and the CO 2 emission had stopped by the end of the year. The 1970 eruption of Hekla started at 9:23 pm on 5 May 1970 and lasted until 5 July. It had
2754-474: The 12.5 km (4.8 sq mi) Nordurhraun . In total around 0.3 km (0.072 cu mi) of lava and 5 × 10 m (1.8 × 10 cu ft) of tephra were produced. An eruption may have occurred around 1440 at Raudölder ; despite being close to Hekla this is not classed as an eruption of Hekla based on the SiO 2 content of the lava. Details of the 1510 eruption were not recorded until
2835-596: The 946 AD eruption. Its tree rings are being studied and many new discoveries are being made about North Korea during that time. In northeastern China, a large volcanic eruption in the early Cretaceous caused the fossilization of an entire ecosystem known as the Jehol Biota when powerful pyroclastic flows inundated the area. The deposits include many perfectly preserved fossils of dinosaurs , birds , mammals , reptiles , fish , frogs , plants , and insects . Europe's volcanoes provide unique information about
2916-479: The Lava Crater. The longest lava stream produced was 8 km (5.0 mi) long and stopped in Stóraskógsbotnar. A scientist filming one of the lava streams on 2 November was hit by a block of lava and was killed. The lava flow stopped after 13 months on 21 April, having covered 40 km (15 sq mi) and with a maximum depth of 100 m (330 ft). The lava beds produced were mainly
2997-671: The Shoulder Crater had a 960 m (3,150 ft) circumference at its top and the Summit Crater a 700 m (2,300 ft)circumference at its highest point, 90 m (300 ft) above the ridge. Sandy tephra and ash fell over Iceland in May and June, sometimes making it dark in the daytime near Hekla. The tephra caused fluorine poisoning of grazing sheep, making them unable to walk. That winter more craters formed, building up cones. Explosive activity had ceased six months after
3078-459: The SiO 2 content of the lava. The eruption of 1766 was large (VEI-4) and produced the second largest lava flow, 1.3 km (0.31 cu mi) covering 65 km (25 sq mi), and third largest tephra volume, 0.24 km (0.058 cu mi), of any Icelandic volcano during the inhabited era. The eruption started at around 3:30 am on 5 April 1766 and ceased in May 1768. Initially
3159-416: The Year (2024 values) column used IntCal20 for H-5 and H-3 and ice core data for H-4 which were not available in 2019. Hekla 3, 4, and 5 produced huge amounts of rhyolitic ash and tephra, covering 80% of Iceland and providing useful date markers in soil profiles in other parts of Europe such as Orkney , Scandinavia, and elsewhere. H 3 and H 4 produced the largest layers of tephra in Iceland since
3240-399: The areas west and southwest of Hekla, leading to many cattle deaths, probably mainly from fluorosis . In late 1389 Hekla erupted again (VEI-3), starting with a large ejection of tephra to the southeast. Later "the eruption fissure moved itself out of the mountain proper and into the woods a little above Skard". Skard and another nearby farm were destroyed by a large lava flow that now forms
3321-432: The crater, the lava-stream was between forty and fifty feet deep and nearly a mile in width. On 12 October a fresh torrent of lava burst forth, and heaped up another similar mass. The mountain continued in a state of activity up to April 1846; then it rested for a while, and began again in the following month of October. Since then, however, it has enjoyed repose. The effects of these eruptions were disastrous. The whole island
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3402-470: The eastern Pacific's Nazca Plate, there are twenty one active volcanoes in southern Peru . In 2006, fossils, found under a layer of volcanic ash in Peru, were excavated by a team of paleontologists led by Mark D. Uhen, professor at George Mason University. The fossils were identified as 3 different types of archaeocetes, prehistoric whales, and are older than 36.61 million years which, as of 2011, makes them
3483-594: The entire eruption, which also caused lahars and tsunami . The tephra was deposited to the northwest, destroying and damaging farms and woodland in Þjórsárdalur, Land, Hreppar and Biskupstungur . Fine ash from the eruption reached Norway. There was damage to wildlife with significant numbers of trout , salmon , ptarmigan and farm animals dying. A very small eruption, possibly only VEI-1, took place on 2 April 1725, producing flows of lava from locations around Hekla which have since been covered by later lava flows. These eruptions are not classed as of Hekla itself based on
3564-534: The eruption had started, ash fell on Helsinki , Finland, having covered 2,860 km (1,780 mi) in this time. The initial tephra production rate in the first 30 minutes of the eruption was 75,000 m ·s , dropping to 22,000 m ·s for the next half-hour. The initial phase produced 0.18 km (0.043 cu mi) of tephra, equating to 4.5 × 10 km (1.1 × 10 cu mi) of Dense-rock equivalent , covering 3,130 km (1,210 sq mi) of land and sea. 98 farms were damaged by
3645-455: The eruption intensity until it covered a 4 km (2.5 mi) fissure on the ridge. The cloud from the eruption had ascended to a height of 30 km by 7:08 am, the wind then carried it southwards towards Eyjafjallajökull , turning it black. Pumice first landed on Fljótshlíð at around 7:10 am, and tephra and ash continued falling until it formed a 3–10 cm (1.2–3.9 in) layer. A lava bomb that landed 32 km (20 mi) from Hekla
3726-475: The eruption, but only 2 were no longer farmed in 1970. A large volunteer effort was mobilized to clear the tephra – around 1000 man-days by the end of July. The eruption produced around 3 ML (110 × 10 ^ cu ft) of water (snowmelt and directly from the fissure) which caused flooding of the Ytri Rangá river. In the first 20 hours of the eruption approximately 3,500 m ·s of lava
3807-488: The evening of the eruption; the largest had a magnitude of 4. The eruption started weakly at 9:23 pm IMT ± 2 min before increasing in power. The first pumice fell on Búrfell power station, 15 km (9.3 mi) away, at 9:35 pm causing people to evacuate. The eruption seems to have started in two locations at the same time – to the Shoulder crater's south-southwest and below the Lava Crater. At 10:30 pm
3888-556: The first eruption. Lava flowed from the Lava Crater continuously during the eruption, starting at a rate of over 100 m ·s , dropping to 5–10 m ·s in April and early May at a speed of around 20 cm·s before increasing, eventually reaching 150 m ·s at the end of June and at similar levels until mid-July with a peak flow speed of 2–2.5 m·s . From there it gradually decreased to under 10 m ·s in November. Initially
3969-421: The fish, and the sheep fled in terror from the adjoining heaths, some being burnt before they could escape. On the night of 15 September, two new openings were formed — one on the eastern, and the other on the southern slope — from both of which lava was discharged for twenty-two hours. It flowed to a distance of upwards of twenty miles, killing many cattle and destroying a large tract of pasturage. Twelve miles from
4050-509: The fossils record, and learn about prehistoric cultures and ecosystems. For example, carbonatite tephra found at Oldoinyo Lengai (a volcano in the East African Rift Valley) has buried and preserved fossilized footprints of humans near the site of the eruption. Under certain conditions, volcanic blocks can be preserved for billions of years and can travel up to 400 km away from the eruption. Volcanic eruptions around
4131-425: The ground, they remain as tephra unless hot enough to fuse into pyroclastic rock or tuff . When a volcano explodes, it releases a variety of tephra including ash, cinders, and blocks. These layers settle on the land and, over time, sedimentation occurs incorporating these tephra layers into the geologic record. Tephrochronology is a geochronological technique that uses discrete layers of tephra—volcanic ash from
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#17327653192084212-489: The history of Italy . One example is Mount Vesuvius , a stratovolcano located in southern Italy, which last erupted in March 1944. Earlier, in 79 AD, in an eruption which lasted 12 to 18 hours, Vesuvius had covered the city of Pompeii in molten lava, ash, pumice, volcanic blocks, and toxic gases. Much of the town was preserved and organic materials fossilized by the volcanic ash, and that has provided valuable information about
4293-467: The largest boulders falling to the ground quickest, therefore closest to the vent, while smaller fragments travel further – ash can often travel for thousands of miles, even circumglobal, as it can stay in the stratosphere for days to weeks following an eruption. When large amounts of tephra accumulate in the atmosphere from massive volcanic eruptions (or from a multitude of smaller eruptions occurring simultaneously), they can reflect light and heat from
4374-409: The last thousand years has come from Hekla, amounting to 5 km (1.2 cu mi). Cumulatively, the volcano has produced one of the largest volumes of lava of any in the world in the last millennium, around 8 km (1.9 cu mi). In Icelandic Hekla is the word for a short hooded cloak, which may relate to the frequent cloud cover on the summit. An early Latin source refers to
4455-474: The lava comprised 57–58% SiO 2 and 11% Fe 2 O 3 , from the time of peak flow onwards this changed to 54% SiO 2 and 13.5% Fe 2 O 3 . The lava river sometimes ran through lava tubes before emerging again. The lava front had a height of up to 15 m (49 ft). On 15 and 16 June, a branch of lava flow to the south of Melfell traveled over 1 km (0.62 mi) in 30 hours before slowing and stopping by 21 June, 7.8 km (4.8 mi) from
4536-555: The main crater, one had an area of 6 m (65 sq ft) and a likely weight of 12 tons. Xenoliths formed around 2% of the material produced by the craters. These were of rock types including basalt, andesite, ignimbrite and sedimentary rock . The eruption became stronger at Skjólkvíar on 12 May, with columns of steam attaining a height of 2,500 m (8,200 ft). The eruption intensity then gradually reduced until it stopped on 20 May. The lava field then had an area of 5.8 km (2.2 sq mi). Later that day
4617-552: The monk Benedeit from c. 1120 about the voyages of Saint Brendan mentions Hekla as the prison of Judas . In the Flatey Book Annal it was recorded that during the 1341 eruption, people saw large and small birds flying in the mountain's fire which were taken to be souls. In the 16th century Caspar Peucer wrote that the Gates of Hell could be found in "the bottomless abyss of Hekla Fell". The belief that Hekla
4698-456: The mountain as Mons Casule . After the eruption of 1104, stories, probably spread deliberately through Europe by Cistercian monks, told that Hekla was the gateway to Hell. The Cistercian monk Herbert of Clairvaux wrote in his De Miraculis (without naming Hekla): The renowned fiery cauldron of Sicily , which men call Hell's chimney ... that cauldron is affirmed to be like a small furnace compared to this enormous inferno. A poem by
4779-512: The northeast, producing two main lava fountains, and shortly after another adjoining fissure opened producing lava fountains to a height of 500 m (1,600 ft). At around midnight, another fissure opened northwest of the Lava Crater, later hurling an over 300 m (980 ft) long lava fountain, 200–300 m (660–980 ft) into the air. By midnight lava had already covered over 1 km (0.39 sq mi) and this extended to 7.5 km (2.9 sq mi) by next morning implying
4860-422: The number of active craters decreased, the most active of these built a cone 100 m (330 ft) higher than the level of the ridge. Lava flowed from its base until mid-June when the lava cut through the north crater wall. The larger cones produced more tephra, occasionally with lightning within the tephra cloud. By 5 July, the eruption had stopped. During eruptions of Hekla, fluorine is produced and sticks to
4941-438: The potential for pyroclastic flows . Other or the later part of eruptions come from thinner basalt tending magma which forms lava fields. The tephra produced by its eruptions is high in fluorine , which is poisonous to animals. Hekla's basaltic andesite lava generally has a SiO 2 content of over 54%, compared to the 45–50% of other nearby transitional alkaline basalt eruptions (see TAS classification ). It
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#17327653192085022-696: The same directions leading to many livestock deaths through fluorosis for the next two years. A small eruption (VEI-2) occurred between 27 February 1878 and April 1878, around 10 km (6.2 mi) east of Hekla, and produced 0.2 km (0.048 cu mi) of lava from two parallel fissures covering 15.5 km (6.0 sq mi). A small eruption (VEI-2) occurred between 25 April 1913 and 18 May 1913, around 10 km (6.2 mi) east of Hekla, and caused large fissures at Mundafell and Lambafit which produced 3.8 and 6.3 km (1.5 and 2.4 sq mi) of lava respectively. The VEI-4 eruption started on 29 March 1947 and ended on 21 April 1948. It
5103-446: The same term [REDACTED] This disambiguation page lists articles associated with the title Hecla . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Hecla&oldid=1200986582 " Categories : Disambiguation pages Place name disambiguation pages Hidden categories: Short description
5184-596: The size of the eruption. Tephra fragments are classified by size: The use of tephra layers, which bear their own unique chemistry and character, as temporal marker horizons in archaeological and geological sites, is known as tephrochronology . The word "tephra" and "pyroclast" both derive from Greek : The word τέφρα ( téphra ) means "ash", while pyroclast is derived from the Greek πῦρ ( pyr ), meaning "fire", and κλαστός ( klastós ), meaning "broken in pieces". The word τέφραv (means "ashes")
5265-467: The smoke. By the fourth, fifth, and sixth days, the eruption was greatly diminished, and only the shoulder and summit craters were erupting explosively. The explosive eruption increased in strength from 9–12 April and then from 28 April it reduced again. On 3 May, the volcano stopped throwing out lava in sudden explosions from its craters and changed to continuously ejecting tephra and ash for long periods, until early June when this reduced. On 2 September,
5346-469: The south-southeast, damaging Mýrdalur . A small (VEI-3) eruption began on 8 May 1636 and lasted for over a year. The 5 × 10 m (1.8 × 10 cu ft) of tephra from the eruption damaged pasture to the northeast causing death of livestock. Starting 13 January and lasting for over 7 months the eruption was one of Hekla's most destructive (VEI-4). Initially tephra was produced at 60,000 m ·s , 0.18 km (0.043 cu mi) during
5427-403: The south-southwest on 10 May and in Hlídargígar on 20 May, but a new fissure opened on the same day and lava flowed from this until 5 July. The lava was andesite containing olivine, similar to the lava produced later in the eruption of 1947. Before the eruption, a greater than normal amount of snow melting had occurred, indicating the volcano was heating up. Earth tremors began at 8:48 pm on
5508-404: The sun back through the atmosphere, in some cases causing the temperature to drop, resulting in a temporary " volcanic winter ". The effects of acidic rain and snow, the precipitation caused by tephra discharges into the atmosphere, can be seen for years after the eruptions have stopped. Tephra eruptions can affect ecosystems across millions of square kilometres or even entire continents depending on
5589-470: The surfaces of the grains of tephra. Fine grains can have a fluorine content of 350 ppm, and fluorine poisoning can start in sheep at a diet with fluorine content of 25 ppm. At 250 ppm, death can occur within a few days. In 1783, 79% of the Icelandic sheep stock were killed, probably as a result of fluorosis caused by the eruption of Lakagígar . Some of the ash produced in this eruption had
5670-536: The topography of nearby areas. In Yellowstone National Park , eruption-related flooding caused trees to collapse and wash into lake beds where they fossilized. Nearby forests were flooded, removing bark, leaves, and tree limbs. In 2006, the Augustine Volcano in Alaska erupted generating earthquakes, avalanches , and projected tephra ash approximately two hundred and ninety kilometers away. This dome volcano
5751-533: The volcano since the year 1210. During the Middle Ages , the Icelandic Norse called the volcano the "Gateway to Hell " and the idea spread over much of Europe. The volcano's frequent large and often initially explosive eruptions have covered much of Iceland with tephra , and these layers can be used to date eruptions of Iceland's other volcanoes. Approximately 10% of the tephra created in Iceland in
5832-400: The world have provided valuable scientific information on local ecosystems and ancient cultures. The Waw an Namus volcano is surrounded by an apron of dark tephra, which has a notable color contrast to the surrounding Sahara Desert . Africa's volcanoes have had an impact on the fossil record. Geographically a part of Africa, El Hierro is a shield volcano and the youngest and smallest of
5913-430: Was 0.5 m (1 ft 8 in) across and weighed 20 kg (44 lb). Between Vatnafjöll and Hekla, a layer of tephra up to 1 m (3 ft 3 in) thick was deposited, and this included bombs with a diameter larger than 0.5 m (1 ft 8 in). Bombs with surface areas of 50 m (540 sq ft) were dropped onto the slopes of Hekla, for up to 1 km (0.62 mi). 51 hours after
5994-449: Was also expelled. The tephra caused significant damage to the settlements of Skagafjörður and Fljót, leading to over 500 deaths that winter. The material output from this eruption had SiO 2 levels of between 56% and 64%, and apart from a slight abundance of olivine the lava, was typical of Hekla eruptions. A small eruption (VEI-3) started on 19 May and deposited around 5 × 10 km (1.2 × 10 cu mi) of tephra over
6075-480: Was dormant for more than sixty years before 1845, when it suddenly burst forth on 2 September at 9 am: After a violent storm on the night of the 2nd of September in that year, the surface of the ground in the Orkney Islands was found strown with volcanic dust. There was thus conveyed to the inhabitants of Great Britain an intimation that Hecla had been again at work. Accordingly, tidings soon after arrived of
6156-562: Was produced at 20,000 m ·s . The tephra deposition of a total amount of 0.17 km (0.041 cu mi) was mainly to the east-southeast; immediately to the east of Hekla the layer was 20–40 cm (7.9–15.7 in) deep. Fine ash was carried to the Faroes , Shetland and Orkney. Lava flows to the west and north-west covered an area of 25 km (9.7 sq mi) with a volume of 0.63 km (0.15 cu mi) of lava. Large quantities of dark ash were deposited over pasture in
6237-480: Was produced from the fissure, dividing into various branches and covering 12–15 km (4.6–5.8 sq mi). On the second day, 8 distinct eruption columns were discernible. A crater formed at 860 m (2,820 ft) called the Lava Crater ( Hraungígur ), producing a constant flow of lava. Another crater named the Shoulder Crater ( Axlargígur ) produced a column of smoke every 10 seconds together with loud explosions that created visible compression waves in
6318-495: Was strewn with volcanic ash, which, where it did not smother the grass outright, gave it a poisonous taint. The cattle that ate of it were attacked by a murrain , of which great numbers died. The ice and snow, which had gathered about the mountain for a long period of time, were wholly melted by the heat. Masses of pumice weighing nearly half a ton were thrown to a distance of between four and five miles. The eruption ceased around 5 April 1846. Initially in this VEI-4 eruption tephra
6399-649: Was the Hekla 3 (or H 3 ) eruption c. 1000 BC , which threw about 7.3 km (1.8 cu mi) of volcanic rock into the atmosphere, placing its Volcanic Explosivity Index (VEI) at 5. This would have cooled temperatures in the northern parts of the globe for a few years afterwards. Traces of this eruption have been identified in Scottish peat bogs , and in Ireland a study of tree rings dating from this period has shown negligible tree ring growth for
6480-433: Was the gate to Hell persisted until the 19th century. There is still a legend that witches gather on Hekla during Easter . Hekla is part of a volcanic ridge, 40 km (25 mi) long. The most active part of this ridge, a fissure about 5.5 km (3.4 mi) long named Heklugjá [ˈhɛhklʏˌcauː] , is considered to be within Hekla proper. Hekla looks rather like an overturned boat, with its keel being
6561-528: Was the second largest tephra eruption in the country in historical times with a VEI of 5. Farms upwind of the volcano 15 km (9.3 mi) in Þjórsárdalur valley, 50 km (31 mi) at Hrunamannaafréttur and 70 km (43 mi) at Lake Hvítárvatn were abandoned because of the damage. The eruption caused Hekla to become famous throughout Europe. A VEI-4 eruption began on 19 January 1158 producing over 0.15 km (0.036 cu mi) of lava and 0.2 km (0.048 cu mi) of tephra. It
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