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51-494: Eldvörp–Svartsengi is located in the southwest of Iceland, in the west of the Southern Peninsula, which forms the southwest tip of the country. The Icelandic toponym Svartsengi, literally "black meadow", designates a small valley at the foot of Sýlingarfell. From here, Keflavík and its eponymous international airport are 15 km (9.3 mi) to the northwest, the port town of Vogar is 11 km (6.8 mi) to

102-400: A chilled margin is often found on the intrusion side of the contact, while a contact aureole is found on the country rock side. The chilled margin is much finer grained than most of the intrusion, and may be different in composition, reflecting the initial composition of the intrusion before fractional crystallization, assimilation of country rock, or further magmatic injections modified

153-402: A layered intrusion . The ultimate source of magma is partial melting of rock in the upper mantle and lower crust . This produces magma that is less dense than its source rock. For example, a granitic magma, which is high in silica, has a density of 2.4 Mg/m , much less than the 2.8 Mg/m of high-grade metamorphic rock. This gives the magma tremendous buoyancy, so that ascent of the magma

204-565: A volcanic explosivity index of 1 to 3, which produce lava flows and limited projections of tephras . During the Holocene, the Svartsengi experienced between twelve and fifteen eruptive periods – a periodicity of approximately 1,000 years – as evidenced by the lava flows associated with it. These recurring activities are represented by a close succession of eruptions over a period of several decades. The last of these eruptions took place in

255-506: A contact aureole, and often contain xenolithic fragments of country rock suggesting brittle fracturing. Such intrusions are interpreted as occurring at shallow depth, and are commonly associated with volcanic rocks and collapse structures. An intrusion does not crystallize all minerals at once; rather, there is a sequence of crystallization that is reflected in the Bowen reaction series . Crystals formed early in cooling are generally denser than

306-423: A large event". Following an earthquake swarm warning in the early hours of the 14 January 2024, those that had returned to the town of Grindavík were re-evacuated shortly before further fissure eruptions, with lava entering the town and destroying three structures. This eruption only lasted two days; however, as of 17 January 2024, there was still measurable magma influx below Sundhnúkar and Grindavík, which meant that

357-466: A magnitude of 3. At the same time, the ground rose by more than five centimeters, mainly at around 1.5 km (0.93 mi) to the south-west of the Blue Lagoon and northwest of Þorbjörn. These phenomena were interpreted as the intrusion of magma at a depth of four to five kilometres (2.5 to 3 mi) below the sector most affected by soil uplift. Such events had already occurred in 2020 and 2022 in

408-425: A series of small earthquakes that began at around 21:00 local time. The Icelandic Meteorological Office stated that the eruption stemmed from a fissure with a length of about 3.5 km (2.2 mi), with lava flowing at a rate of around 100 to 200 cubic metres per second (3,500 to 7,100 cu ft/s). An Icelandic Civil Defence official told RUV that the eruption had happened quickly and appeared to be "quite

459-422: A span of 16 days. Following a substantial subsidence of 35 cm (14 in) on that date, a new phase of activity led to a land rise of about 30 cm (12 in) by December 8, which surpassed the level that was previously reached before 10 November. On the evening of 18 December 2023, a volcanic eruption began near Hagafell [ˈhaːɣaˌfɛtl̥] , about 4km (2.5 miles) north-east of Grindavík, following

510-412: A synonym for all igneous intrusions; as a dustbin category for intrusions whose size or character are not well determined; or as a name for a very large intrusion or for a crystallized magma chamber . A pluton that has intruded and obscured the contact between a terrane and adjacent rock is called a stitching pluton . Intrusions are broadly divided into discordant intrusions , which cut across

561-464: Is subpolar oceanic ( Köppen : Cfc ) with cool summers and moderately cold winters. There is not a truly dry month but June is the month that gets the least amount of precipitation. Winter high temperatures average above the freezing mark, and summer high temperatures are cool to mild. The warmest month on average is July with an average high of 14.2 °C (58 °F) and the coldest is January with an average high of 3.4 °C (38 °F). The town

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612-860: Is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth . Intrusions have a wide variety of forms and compositions, illustrated by examples like the Palisades Sill of New York and New Jersey ; the Henry Mountains of Utah ; the Bushveld Igneous Complex of South Africa ; Shiprock in New Mexico ; the Ardnamurchan intrusion in Scotland; and

663-404: Is inevitable once enough magma has accumulated. However, the question of precisely how large quantities of magma are able to shove aside country rock to make room for themselves (the room problem ) is still a matter of research. The composition of the magma and country rock and the stresses affecting the country rock strongly influence the kinds of intrusions that take place. For example, where

714-408: Is particularly important in classifying intrusive igneous rocks. Intrusions must displace existing country rock to make room for themselves. The question of how this takes place is called the room problem , and it remains a subject of active investigation for many kinds of intrusions. The term pluton is poorly defined, but has been used to describe an intrusion emplaced at great depth; as

765-783: Is represented in sports by Íþrótta- og ungmennafélag Keflavíkur . The former NATO military base Naval Air Station Keflavik is used as a setting for an important story line in Tom Clancy 's novel Red Storm Rising . Clancy speculated about the base, the geography, local flora, and the station equipment. NAS Keflavik is also a central setting in Icelandic writer Arnaldur Indriðason's 1999 mystery Napóleonsskjölin , translated into English in 2011 as Operation Napoleon . [REDACTED] Media related to Keflavík at Wikimedia Commons Igneous intrusion In geology , an igneous intrusion (or intrusive body or simply intrusion )

816-581: The Coastal Batholith of Peru is 1,100 kilometers (680 mi) long and 50 kilometers (31 mi) wide. They are usually formed from magma rich in silica , and never from gabbro or other rock rich in mafic minerals, but some batholiths are composed almost entirely of anorthosite . A sill is a tabular concordant intrusion, typically taking the form of a sheet parallel to sedimentary beds. They are otherwise similar to dikes. Most are of mafic composition, relatively low in silica, which gives them

867-723: The Cold War , Naval Air Station Keflavik played an important role in monitoring marine and submarine traffic from the Norwegian and Greenland seas into the Atlantic Ocean . Forces from the United States Air Force were added to provide radar monitoring, fighter intercept, in-flight refueling, and aerial/marine rescue. With increasing ranges for aircraft and the dissolution of the Soviet Union ,

918-532: The Sierra Nevada Batholith of California . Because the solid country rock into which magma intrudes is an excellent insulator , cooling of the magma is extremely slow, and intrusive igneous rock is coarse-grained ( phaneritic ). Intrusive igneous rocks are classified separately from extrusive igneous rocks, generally on the basis of their mineral content. The relative amounts of quartz , alkali feldspar , plagioclase , and feldspathoid

969-518: The 13th century with the " Reykjanes fires ", a series of effusive eruptions on Svartsengi and Reykjanes, which took place between 1210 and 1240 and which produced lava flows with an area of 50 km (19 sq mi) for Svartsengi alone. In December 2019 volcanic activity began near the hyaloclastite mountain Þorbjörn, which indicated that the Reykjanes Peninsula was beginning a new volcanic cycle after 800 years of inactivity. In

1020-572: The Svartsengi volcanic system consists of a set of fissures, cones and volcanic craters aligned over 30 km (19 mi) in length and 7 km (4.3 mi) in width, oriented north-east to south-west and surrounded by fields of lava: Þorbjörn (243 m (797 ft)), Hagafell (158 m (518 ft)), Sundhnúkur 134 m (440 ft) ( Sundhnúksgígar means the associated crater row), Sýlingarfell (206 m (676 ft)), Stóra-Skógfell (188 m (617 ft)), and Litla-Skógfell (85 m (279 ft)) are named volcanic hills from

1071-500: The Svartsengi, there are relay antennas; and to the south, on the edge of the volcano, stand the antennas of the Naval Radio Transmitter Facility Grindavik . The majority of Svartsengi is located in the municipality of Grindavíkurbær , with the exception of the northeastern end of the fissures which are found in that of Vogar, both in the region of Suðurnes. Lacking a central volcanic cone,

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1122-431: The area caused a swarm of intense earthquakes to begin. Several hundred tremors were detected daily with hypocenters between 6 and 1.5 kilometres (3.7 and 0.9 mi) deep, the vast majority of magnitude less than 3 but a few exceeding this value, up to 4.5 for the most powerful. On 27 October the alert level for aviation was reassessed to yellow. By 1 November, 10,000 tremors had already been recorded, including 26 exceeding

1173-468: The base became less important, and the last U.S. personnel were withdrawn in 2006. Within Iceland, Keflavík was renowned as a rich source of musicians during the 1960s and 1970s, and came to be known as bítlabærinn [ˈpihtlaˌpaiːrɪn] or " The Beatle Town". The local geography is dominated by fields of basalt rubble, interspersed with a few hardy plants and mosses. The climate of Keflavík

1224-447: The case given the continued evidence for magma accumulation. At 12:46 UTC on 29 May 2024, a further vigorous eruption commenced. After 24 days with a volume and area of its lava flows that were the largest of the five eruptions to date, it ceased on 22nd June. The 6th eruption in the series started about 21:25 UTC 22nd August 2024 and finished on 6th September 2024. The 7th eruption commenced at 23:14 20 November 2024 UTC. The proximity to

1275-423: The composition of the rest of the intrusion. Isotherms (surfaces of constant temperature) propagate away from the margin according to a square root law, so that if the outermost meter of the magma takes ten years to cool to a given temperature, the next inward meter will take 40 years, the next will take 90 years, and so on. This is an idealization, and such processes as magma convection (where cooled magma next to

1326-461: The contact between intrusion and country rock give clues to the conditions under which the intrusion took place. Catazonal intrusions have a thick aureole that grades into the intrusive body with no sharp margin, indicating considerable chemical reaction between intrusion and country rock, and often have broad migmatite zones. Foliations in the intrusion and the surrounding country rock are roughly parallel, with indications of extreme deformation in

1377-416: The contact is given by the relationship T / T 0 = 1 2 + 1 2 erf ⁡ ( x 2 k t ) {\displaystyle T/T_{0}={\frac {1}{2}}+{\frac {1}{2}}\operatorname {erf} ({\frac {x}{2{\sqrt {kt}}}})} where T 0 {\displaystyle T_{0}} is the initial temperature of

1428-468: The contact sinks to the bottom of the magma chamber and hotter magma takes its place) can alter the cooling process, reducing the thickness of chilled margins while hastening cooling of the intrusion as a whole. However, it is clear that thin dikes will cool much faster than larger intrusions, which explains why small intrusions near the surface (where the country rock is initially cold) are often nearly as fine-grained as volcanic rock. Structural features of

1479-510: The country rock. Such intrusions are interpreted as taking placed at great depth. Mesozonal intrusions have a much lower degree of metamorphism in their contact aureoles, and the contact between country rock and intrusion is clearly discernible. Migmatites are rare and deformation of country rock is moderate. Such intrusions are interpreted as occurring at medium depth. Epizonal intrusions are discordant with country rock and have sharp contacts with chilled margins, with only limited metamorphism in

1530-501: The crust is undergoing extension, magma can easily rise into tensional fractures in the upper crust to form dikes. Where the crust is under compression, magma at shallow depth will tend to form laccoliths instead, with the magma penetrating the least competent beds, such as shale beds. Ring dikes and cone sheets form only at shallow depth, where a plug of overlying country rock can be raised or lowered. The immense volumes of magma involved in batholiths can force their way upwards only when

1581-516: The existing structure of the country rock, and concordant intrusions that intrude parallel to existing bedding or fabric . These are further classified according to such criteria as size, evident mode of origin, or whether they are tabular in shape. An intrusive suite is a group of intrusions related in time and space. Dikes are tabular discordant intrusions, taking the form of sheets that cut across existing rock beds. They tend to resist erosion, so that they stand out as natural walls on

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1632-448: The exposure may be only the tip of a larger intrusive body, the classification is meaningful for bodies which do not change much in area with depth and that have other features suggesting a distinctive origin and mode of emplacement. Batholiths are discordant intrusions with an exposed area greater than 100 square kilometers (39 sq mi). Some are of truly enormous size, and their lower contacts are very rarely exposed. For example,

1683-401: The field, there is geochemical evidence. Zircon zoning provides important evidence for determining if a single magmatic event or a series of injections were the methods of emplacement. Large felsic intrusions likely form from melting of lower crust that has been heated by an intrusion of mafic magma from the upper mantle. The different densities of felsic and mafic magma limit mixing, so that

1734-499: The following years, multiple magmatic intrusions have formed in the Eldvörp-Svartsengi volcanic system, the first four of which stalled before reaching the surface. During this time volcanic unrest on the peninsula was mostly associated with the neighbouring Fagradalsfjall system, where three out of four confirmed magmatic intrusions culminated in volcanic eruptions. On 24 October 2023, a new magmatic intrusion underneath

1785-538: The formation of calderas . Volcanic necks are feeder pipes for volcanoes that have been exposed by erosion . Surface exposures are typically cylindrical, but the intrusion often becomes elliptical or even cloverleaf -shaped at depth. Dikes often radiate from a volcanic neck, suggesting that necks tend to form at intersections of dikes where passage of magma is least obstructed. Diatremes and breccia pipes are pipe-like bodies of breccia that are formed by particular kinds of explosive eruptions . As they have reached

1836-544: The geochemical composition of their lavas, and also a certain individuality in their topography and location, which has tended volcanologists to consider them with time as systems distinct from each other. Together with Reykjanes, Fagradalsfjall, Krýsuvík and Brennisteinsfjöll , Svartsengi is part of the Reykjanes volcanic belt . The lavas emitted by the Svartsengi are exclusively basalts —notably picrite and tholeite —and emerge through effusive eruptions with

1887-407: The hot material, k is the thermal diffusivity (typically close to 10 m s for most geologic materials), x is the distance from the contact, and t is the time since intrusion. This formula suggests that the magma close to the contact will be rapidly chilled while the country rock close to the contact is rapidly heated, while material further from the contact will be much slower to cool or heat. Thus

1938-452: The landscape. They vary in thickness from millimeter-thick films to over 300 meters (980 ft) and an individual sheet can have an area of 12,000 square kilometers (4,600 sq mi). They also vary widely in composition. Dikes form by hydraulic fracturing of the country rock by magma under pressure, and are more common in regions of crustal tension. Ring dikes and cone sheets are dikes with particular forms that are associated with

1989-541: The low viscosity necessary to penetrate between sedimentary beds. A laccolith is a concordant intrusion with a flat base and domed roof. Laccoliths typically form at shallow depth, less than 3 kilometers (1.9 mi), and in regions of crustal compression. Lopoliths are concordant intrusions with a saucer shape, somewhat resembling an inverted laccolith, but they can be much larger and form by different processes. Their immense size promotes very slow cooling, and this produces an unusually complete mineral segregation called

2040-517: The magma is highly silicic and buoyant, and are likely do so as diapirs in the ductile deep crust and through a variety of other mechanisms in the brittle upper crust. Igneous intrusions may form from a single magmatic event or several incremental events. Recent evidence suggests that incremental formation is more common for large intrusions. For example, the Palisades Sill was never a single body of magma 300 meters (980 ft) thick, but

2091-497: The most populated cities in the country, including Reykjavík, and the significant geothermal potential of the site led to the construction of the Svartsengi Power Station, commissioned in 1977. The water discharged near the power plant was heavily loaded with minerals, most notably in silica, and formed a silty body of water in the lava field, leading eventually to the construction of the Blue Lagoon in 1992. During

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2142-577: The municipality of Reykjanesbær . Keflavík International Airport , the country's largest airport (serving nearby Reykjavík ) is adjacent to the town. Keflavík was founded by Scottish entrepreneurs and engineers in the 16th century, and developed on account of its fishing and fish processing industry. In the 1940s an airport was built next to the town by the United States military , which served as an important refueling stop for trans-Atlantic flights, especially during World War II . During

2193-459: The north, the port town of Grindavík is 4 km (2.5 mi) to the south, and the cape Reykjanes 16 km (9.9 mi) to the southwest. Reykjavík , the national capital, is about 30 km (19 mi) to the northeast. The Svartsengi Power Station and the Blue Lagoon , served by routes 43 and 426 , are located on the volcanic system. At the top of Þorbjörn, the highest point of

2244-449: The possibility of additional fissures opening in the coming days remained elevated. The next eruption commenced on the early morning of 8th February 2024, stopped the next day, and was followed by a diking event that did not reach the surface on 2 March 2024. On the evening of 16th March a further eruption occurred between Hagafell and Stóra-Skógfell. This eruption ceased on 9th of May, having not increased in power, as some speculated might be

2295-459: The same sector without this leading to an eruption. On 9 November 2023, seismicity reached levels close to 5 on the Richter scale, which led to the decision to close the Blue Lagoon as a precaution. The frequency and intensity of the earthquakes dramatically increased on 10 November, with 20,000 tremors recorded by that time, the largest of which exceeded magnitude 5.3. An evacuation was ordered in

2346-456: The seismic activity of November 2023, work was begun on a diversionary berm to protect the plant in case of an eruption. Keflav%C3%ADk Keflavík (pronounced [ˈcʰɛplaˌviːk] , meaning Driftwood Bay ) is a town in the Reykjanes region in southwest Iceland . It is included in the municipality of Reykjanesbær whose population as of 2016 is 15,129. In 1995, Keflavík merged with nearby Njarðvík and Hafnir to form

2397-405: The silicic magma floats on the mafic magma. Such limited mixing as takes place results in the small inclusions of mafic rock commonly found in granites and granodiorites. An intrusion of magma loses heat to the surrounding country rock through heat conduction. Near the contact of hot material with cold material, if the hot material is initially uniform in temperature, the temperature profile across

2448-420: The southwest to the northeast. Two other volcanic systems surround Svartsengi, namely Reykjanes to the west and Fagradalsfjall to the east, both also consisting of a set of fissures, cones and craters oriented in a parallel manner. Thus, although they have similar geological and topographical characteristics, and function on the same tectonic principle in a rift context, they also possess notable differences in

2499-520: The surface they are really extrusions, but the non erupted material is an intrusion and indeed due to erosion may be difficult to distinguish from an intrusion that never reached the surface when magma/lava. The root material of a diatreme is identical to intrusive material nearby, if it exists, that never reached the then surface when formed. A stock is a non-tabular discordant intrusion whose exposure covers less than 100 square kilometers (39 sq mi). Although this seems arbitrary, particularly since

2550-525: The town of Grindavík , which is located near the area of the seismic activity. Large-scale subsidence in and around the town is reported to have caused significant damage. This was due to the movement of magma into a dike beneath the Sundhnúkur craters ( Sundhnúkagígaröðin ), which subsequently propagated south-west under the town. From the beginning of the earthquakes until 10 November, the land at Svartsengi rose by more than 10 cm (4 in) within

2601-401: Was formed from multiple injections of magma. An intrusive body is described as multiple when it forms from repeated injections of magma of similar composition, and as composite when formed of repeated injections of magma of unlike composition. A composite dike can include rocks as different as granophyre and diabase . While there is often little visual evidence of multiple injections in

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