The volcanic system of Krýsuvík (or Krísuvík, both pronounced in Icelandic, also Trölladyngja-Krýsuvík or Krýsuvík-Trölladyngja volcanic system), is situated in the south–west of

Iceland Iceland is a Nordic countries, Nordic island country between the Atlantic Ocean, North Atlantic and Arctic Oceans, on the Mid-Atlantic Ridge between North America and Europe. It is culturally and politically linked with Europe and is the regi ...

on the

Reykjanes Reykjanes () is a small headland on the south-western end of the Reykjanes Peninsula in Iceland, giving the main peninsula its name. Volcanic action is responsible for forming the entire peninsula. The nearest town is Keflavik. The name, , trans ...

peninsula. It is located in the middle of Reykjanes and on the divergent

plate boundary Plate tectonics (, ) is the scientific theory that the Earth's lithosphere comprises a number of large tectonic plates, which have been slowly moving since 3–4 billion years ago. The model builds on the concept of , an idea developed durin ...

of the

Mid-Atlantic Ridge The Mid-Atlantic Ridge is a mid-ocean ridge (a Divergent boundary, divergent or constructive Plate tectonics, plate boundary) located along the floor of the Atlantic Ocean, and part of the List of longest mountain chains on Earth, longest mountai ...

which traverses Iceland. It was named after the

Krýsuvík Krýsuvík (also Krísuvík, both pronounced in Icelandic language, Icelandic) is an area in Southwest (Icelandic constituency), Southwest Iceland at about 35 km from Reykjavík. Geography and access It is situated on the Reykjanes penins ...

area which is part of it and consists of a fissure system without a

central volcano A central volcano is a type of volcano formed by basalts and silica-rich volcanic rocks. They contain very few or no volcanic rocks of intermediate composition, such that they are chemically bimodal volcanism, bimodal. Large silicic eruptions at c ...

.Thorvaldur Thordarson, Ármann Höskuldsson: ''Postglacial volcanism in Iceland. Jökull No. 58'' (2008).
Retrieved 20 August 2020. However, there are some indications—namely, the discovery by

geophysical Geophysics () is a subject of natural science concerned with the physical processes and properties of Earth and its surrounding space environment, and the use of quantitative methods for their analysis. Geophysicists conduct investigations acros ...

methods of what scientists interpret as a buried

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the str ...

, combined with the well-known, vigorous

hydrothermal Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with th ...

system above it—that an embryonic central

magma chamber A magma chamber is a large pool of liquid rock beneath the surface of the Earth. The molten rock, or magma, in such a chamber is less dense than the surrounding country rock, which produces buoyant forces on the magma that tend to drive it u ...

may already exist or be actively developing. The volcanic system has a length of , a width of around , covers an area of , and its highest elevation is . It is one of 4 (or up to 7, depending on the source) volcanic systems situated within the

Reykjanes Volcanic Belt The Reykjanes Peninsula ( ) in southwest Iceland is the continuation of the mostly submarine Reykjanes Ridge, a part of the Mid-Atlantic Ridge, on land and reaching from Esjan, Esja in the north and Hengill in the east to Reykjanestá in the ...

. The volcanic systems are arranged en echelon and at an angle that varies from 20 to 45° to the direction of the rift zone on the divergent plate boundary traversing Reykjanes.

General characteristics

The volcanic system of Krýsuvík has no central volcanic edifice, but rather a fissure swarm that is long, is composed of a mixture of volcanic and tectonic fissures and faults, of which are volcanic fissures. Recent

work on the system, employing

magnetotelluric Magnetotellurics (MT) is an electromagnetic geophysical method for inferring the earth's subsurface electrical conductivity from measurements of natural geomagnetic and geoelectric field variation at the Earth's surface. Investigation depth ran ...

resistivity Electrical resistivity (also called volume resistivity or specific electrical resistance) is a fundamental specific property of a material that measures its electrical resistance or how strongly it resists electric current. A low resistivity i ...

sampling and

modeling A model is an informative representation of an object, person, or system. The term originally denoted the Plan_(drawing), plans of a building in late 16th-century English, and derived via French language, French and Italian language, Italian ult ...

, indicates the presence of a buried

with possibly an embryonic central

beneath the system. This suggests that it could eventually develop into a central volcano like the similar, but more mature

Hengill Hengill () is a volcanic table mountain situated in the south-west of Iceland, to the south of Þingvellir. The volcano is still active, as evidenced by its numerous hot springs and fumaroles, but the last eruption occurred approximately 2,000&n ...

volcanic system farther to the east on the peninsula. There are no known submarine fissures of the system which nevertheless reaches from the south coast in direction south–west to north–east over the Reykjanes Peninsula. The northernmost fissures are thought to reach

Lake Rauðavatn A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from t ...

on the outskirts of

Reykjavík Reykjavík is the Capital city, capital and largest city in Iceland. It is located in southwestern Iceland on the southern shore of Faxaflói, the Faxaflói Bay. With a latitude of 64°08′ N, the city is List of northernmost items, the worl ...

. There are no ice-covered volcanoes connected to the Krýsuvík system, but Lake

Kleifarvatn Kleifarvatn () is the largest lake on the Reykjanesskagi, Reykjanes Peninsula in Iceland, situated in the southern part of the peninsula. It is located on the Fissure vent, fissure zone of the Mid-Atlantic Ridge. The lake has no visible water c ...

lies within the system and

geothermal activity Geothermal activity is a group of natural heat transfer processes, occurring on Earth's surface, caused by the presence of excess heat in the subsurface of the affected area, usually caused by the presence of an igneous intrusion underground. Geot ...

is found at the lake bottom. The Krýsuvík volcanic system has a tendency to

effusive In physics and chemistry, effusion is the process in which a gas escapes from a container through a hole of diameter considerably smaller than the mean free path of the molecules. Such a hole is often described as a ''pinhole'' and the escape ...

basaltic fissure eruptions; the last eruption took place in the 14th century. The

Fagradalsfjall Fagradalsfjall () is an active tuya volcano formed in the Last Glacial Period on the Southern Peninsula (Iceland), Reykjanes Peninsula, around from Reykjavík, Iceland. Fagradalsfjall is also the name for the wider volcanic system covering an ...

fissure swarm that erupted in 2021 was initially considered potentially a branch or a secondary part of the Krýsuvík volcanic system, but it is now usually considered a separate volcanic system. The eruption products of the Krýsuvík system consist exclusively of

basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...

Eruptions

The volcanic system is centered on the divergent plate boundary on Reykjanes peninsula. It is easier there for

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...

to reach the surface, because of the multitude of tectonic and volcanic faults and fissures in such regions. There have been at least 10 volcanic episodes within the volcanic system in the last 8,000 years. These episodes each comprised many single eruptions and were most probably connected to

rift In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear downfaulted depression, called a graben, or more commonly a half-graben ...

ing. Some

Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...

eruptions have been dated specifically, especially the eruption that produced Búrfellshraun (ca. 5290 BP). Since the time of settlement in Iceland, which is thought to have been in the 9th century, more eruptions have taken place within the system, all of them in the

Middle Ages In the history of Europe, the Middle Ages or medieval period lasted approximately from the 5th to the late 15th centuries, similarly to the post-classical period of global history. It began with the fall of the Western Roman Empire and ...

. The

Krýsuvík fires The Krýsuvík fires were a period of volcanic activity in a fissure swarm known as Krýsuvík (volcanic system), Krýsuvík (:is: Krýsuvíkureldar) on the Reykjanes peninsula. The fires started in the middle of the 12th century, probably in ...

were a period of volcanic activity which started in the middle of the 12th century, probably in 1151 and written sources indicate that they ended in 1188. The activity of

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

shield volcano A shield volcano is a type of volcano named for its low profile, resembling a shield lying on the ground. It is formed by the eruption of highly fluid (low viscosity) lava, which travels farther and forms thinner flows than the more viscous lava ...

es such as Þráinskjöldur and Hrútagjá , as well as of

tuya A tuya is a flat-topped, steep-sided volcano formed when lava erupts through a thick glacier or ice sheet. They are rare worldwide, being confined to regions which were covered by glaciers and had active volcanism during the same period. As lava ...

s like

within the volcanic system, are seen as separate from the fissure system, although the bigger volcanoes control parts of the

topography Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the landforms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary sci ...

. The Krýsuvík system has a tendency to phreatic explosions, often within rifting episodes or during eruption series. The underground of Reykjanes peninsula is soaked with water as it has a high groundwater level as well as saline sea water in its cave systems. There is a prehistoric

maar A maar is a broad, low-relief volcanic crater caused by a phreatomagmatic eruption (an explosion which occurs when groundwater comes into contact with hot lava or magma). A maar characteristically fills with water to form a relatively shallow ...

complex around Grænavatn at Krýsuvík which has its origin in phreatic explosions connected to a period of effusive eruptions. There an explosion connected to geothermal activity of an old borehole in 1999 at ''Seltún''. Starting on 27 September 2021, an intense earthquake swarm began that was concentrated around the Keilir region with over 1000 earthquakes with a magnitude 4.2 event on 2 October. The earthquakes sparked concern that a second eruption could begin in the area but it was not known definitely what was causing the swarm. During the overnight hours of 10 October 2021, a strong M3.2 earthquake occurred SSW of Keilier.

List of lava fields

These are some lava fields which originated in eruptions of the Krýsuvík volcanic system since the end of the last glacial spell 13,000 years ago.

Búrfellshraun

Around 8,000 years ago, the Búrfell crater near

Hafnarfjörður Hafnarfjörður, officially Hafnarfjarðarkaupstaður, is a port town and municipality in Iceland, located about south of Reykjavík. The municipality consists of two non-contiguous areas in the Capital Region (Iceland), Capital Region, on the s ...

produced a lava field called . Today, a big part of midtown Hafnarfjörður is built onto and around Búrfellshraun. The crater contains a

lava channel A lava channel is a stream of fluid lava contained within zones of static (i.e., solid and stationary) lava or lava levees. The initial channel may not contain levees per se, until the parental flow solidifies over what develops into the channel a ...

called .

Óbrinnishólabruni

The lavas came 2,000 years ago from some craters near Bláfjallavegur (Road 407) which have since been destroyed by quarrying. The name Óbrinnishólar means that there was no “fire” in them during further eruptions in the region in historical time. Parts of Hafnarfjörður (midtown and ) are located on top of this lava field.

Kapelluhraun

The lavas of (, "chapel lava") from historical time (erupted around 1150) have been given this name because of a medieval chapel whose ruins are still standing on them. A small statue of

Saint Barbara Saint Barbara (; ; ; ), known in the Eastern Orthodox Church as the Great Martyr Barbara, was an Early Christianity, early Christian Greek saint and martyr. There is no reference to her in the authentic early Christian writings nor in the origin ...

was found at the place. The Kapelluhraun lava field consists of

pāhoehoe Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or unde ...

and aā lava which streamed from the highland down to the bay of

Straumsvík Straumsvík (, "stream cove") is a harbour on the northern shore of the Reykjanes Peninsula in Iceland Iceland is a Nordic countries, Nordic island country between the Atlantic Ocean, North Atlantic and Arctic Oceans, on the Mid-Atlantic R ...

near today's

aluminium smelter Aluminium smelting is the process of extracting aluminium from its oxide, alumina, generally by the Hall-Héroult process. Alumina is extracted from the ore bauxite by means of the Bayer process at an List of alumina refineries, alumina refinery. ...

and there into the sea. The events were part of a ca. 30 years long unrest period in the late 12th century which is called ''Krýsuvík Fires''. This unrest period included repeated eruption series and rifting episodes and is recorded in ''

Flateyjarbók ''Flateyjarbók'' (; "Book of Flatey, Breiðafjörður, Flatey") is an important medieval Iceland, Icelandic manuscript. It is also known as GkS 1005 fol. and by the Latin name ''Codex Flateyensis''. It was commissioned by Jón Hákonarson and p ...

''. The eruption fissures had a length of and respectively, and the lava flows cover around . Today it is a

golf course A golf course is the grounds on which the sport of golf is played. It consists of a series of holes, each consisting of a teeing ground, tee box, a #Fairway and rough, fairway, the #Fairway and rough, rough and other hazard (golf), hazards, and ...

is situated in the middle of these lavas, seen when looking from Route 41 between Straumsvík and Hafnarfjörður in direction of

Faxaflói Faxaflói (), sometimes Faxa Bay, Faxe Bay or Faxi Bay,Thorstein Thorsteinsson. 1930. ''Iceland, 1930: A Handbook Published on the Fortieth Anniversary of Landsbanki Íslands (National Bank of Iceland)''. Reykjavík: Ríkisprentsmidjan Gutenberg. ...

Landforms

The Seltún geothermal area is situated next to Krýsuvík in direction of lake

(Route 42) and at the foot of

Sveifluháls Sveifluháls () is a Mafic rock, mafic hyaloclastite ridge of 397 m height in the southwest of Iceland in Gullbringusýsla (Reykjanes Peninsula). It is part of Krýsuvík (volcanic system), Krýsuvík volcanic system and of the protected area ...

hyaloclastite Hyaloclastite is a volcanoclastic accumulation or breccia consisting of glass (from the Greek ''hyalus'') fragments (clasts) formed by quench fragmentation of lava flow surfaces during submarine or subglacial extrusion. It occurs as thin marg ...

ridge. It is a geothermal high temperature area,

hydrothermal alteration Metasomatism (from the Greek μετά ''metá'' "change" and σῶμα ''sôma'' "body") is the chemical alteration of a Rock (geology), rock by hydrothermal and other fluids. It is traditionally defined as metamorphism which involves a change in t ...

has led to a multicolored environment. Here

solfatara A fumarole (or fumerole) is a vent in the surface of the Earth or another rocky planet from which hot volcanic gases and vapors are emitted, without any accompanying liquids or solids. Fumaroles are characteristic of the late stages of volcani ...

fumarole A fumarole (or fumerole) is a vent in the surface of the Earth or another rocky planet from which hot volcanic gases and vapors are emitted, without any accompanying liquids or solids. Fumaroles are characteristic of the late stages of volcani ...

mudpot A mudpot, or mud pool, is a type of acidic hot spring, or fumarole, with limited water. It usually takes the form of a pool of bubbling mud, as a result of the acid and microorganisms decomposing surrounding rock into clay and mud. Description ...

s and

hot spring A hot spring, hydrothermal spring, or geothermal spring is a Spring (hydrology), spring produced by the emergence of Geothermal activity, geothermally heated groundwater onto the surface of the Earth. The groundwater is heated either by shallow ...

s are formed; the soil is coloured bright yellow, red, and green caused by

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

oxidation Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is ...

sulfur Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...

and

calcite Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...

precipitation. The sulfur deposits were mined in 1722–1728 and in the 19th century. The German scientist

Robert Bunsen Robert Wilhelm Eberhard Bunsen (; 30 March 1811 – 16 August 1899) was a German chemist. He investigated emission spectra of heated elements, and discovered caesium (in 1860) and rubidium (in 1861) with the physicist Gustav Kirchhoff. The Bu ...

visited the site in 1845 and, based on research there, proposed a hypothesis on formation of

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...

in nature. Also found in the area are the lava field from the 12th century as well as some

subglacial mounds and formations like

Helgafell Helgafell may refer to: * Helgafell (Hafnarfjörður), a mountain , on the Reykjanes peninsula, south-west Iceland * Helgafell, a mountain , in Mosfellsbær north-east of Reykjavík * Helgafell, a mountain at , in Rangárþing eystra, south-cen ...

and

Trölladyngja Situated in the Ódáðahraun lava field, Trölladyngja () is the biggest of the Icelandic shield volcanoes, reaching a height of above sea level, and rising almost above the surrounding desert and lava fields. It part of the Bárðarbunga vol ...

Geothermal activity

Some active geothermal high temperature areas are to be found in the system, especially at . Since 2009 repeated uplift episodes with earthquake swarms occurred, probably connected to

igneous intrusions Igneous rock ( ), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava. The magma can be derived from partial m ...

and hydrothermal changes.

External links

General information

* Krýsuvík at *

Volcano monitoring

Icelandic Met Office (IMO). Earthquake Monitoring. Reykjanes Peninsula

IMO. Aviation Color Code

Geologist Páll Einarsson explains geology and volcanism of Reykjanes Peninsula as well as the 2020 earthquake series which partially takes place within this volcanic system

RÚV Ríkisútvarpið (, ; abbr. RÚV ) is Iceland's national public broadcasting, public-service broadcasting organization. Founded in 1930, it operates from studios in the country's capital, Reykjavík, as well as regional centres around the count ...

. 20 October 2020. (in Icelandic)

Tourism

Seltún. Visit Reykjanes. Official website.

References

{{Volcanoes of Iceland, state=collapsed Volcanic systems of Iceland Reykjanes Volcanic Belt Krýsuvík Volcanic System Dormant volcanoes