Sveifluháls () is a

mafic A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks include ...

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 of 397 m height in the southwest 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 ...

in Gullbringusýsla (

Reykjanes Peninsula Southern Peninsula (, ) is an administrative unit and part of Reykjanesskagi (pronounced ), or Reykjanes Peninsula, a region in southwest Iceland. It was named after Reykjanes, the southwestern tip of Reykjanesskagi. The region has a populatio ...

). It is part of

Krýsuvík volcanic system Krýsuvík (also Krísuvík, both pronounced in Icelandic) is an area in Southwest Iceland at about 35 km from Reykjavík. Geography and access It is situated on the Reykjanes peninsula between Þorlákshöfn and Grindavík and accessed ...

and of the protected area Reykjanes Fólkvangur.

Geography

The mountain is situated between 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 ...

and the valley ''Móhálsadalur'' . In some parts of the ridge, there are geothermal areas, esp. at

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 ...

and Seltún.Lucía Magali Ramírez-González et al.: ''Remote sensing of surface Hydrothermal Alteration, identification of Minerals and Thermal anomalies at Sveifluháls-Krýsuvík high temperature Geothermal field, SW Iceland.'' 2019 IOP Conf. Ser.: Earth Environ. Sci. 254 012005
Retrieved 25 August 2020. It is located at about 5 km from the southern coast of Reykjanes Peninsula. The ridge actually consists of two parallel narrow ridge segments with a 0,5 km wide valley in between. Sveifluháls is also called ''Austurháls'' in contrast to its parallel ridge on the other side of Móhálsadalur, the ''Núpshlídarháls'' ridge, which is also called ''Vesturháls'' . Road 42 passes by directly at the foot of the mountain between the same and lake Kleifarvatn.

Geology

Sveifluháls is a

basaltic Basalt (; ) is an 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 surface of a rocky planet or moon. More than 90% ...

ridge, actually a "ca. 22 km long tindar complex". G.B.M.Pedersen, P. Grosse: ''Morphometry of subaerial shield volcanoes and glaciovolcanoes from Reykjanes Peninsula, Iceland: Effects of eruption environment.'' Journal of Volcanology and Geothermal Research 282, (2014), 115–133.
/ref> It consists as is usual for such subglacially formed volcanoes, of

pillow lava Pillow lavas are lavas that contain characteristic pillow-shaped structures that are attributed to the extrusion of the lava underwater, or ''subaqueous extrusion''. Pillow lavas in volcanic rock are characterized by thick sequences of discontinu ...

s under a layer of

phreatomagmatic Phreatomagmatic eruptions are volcanic eruptions resulting from interaction between magma and water. They differ from exclusively magmatic eruptions and phreatic eruptions. Unlike phreatic eruptions, the products of phreatomagmatic eruptions conta ...

tephra Tephra is fragmental material produced by a Volcano, volcanic eruption regardless of composition, fragment size, or emplacement mechanism. Volcanologists also refer to airborne fragments as pyroclasts. Once clasts have fallen to the ground, ...

(hyaloclastite). Pedersen and her coworkers think that the

Ice Age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages, and g ...

glacier which was covering it at time of formation had a thickness between 70 and 400 m.

Formation of Sveifluháls

Mercurio postulates that the ridge formation started with eruptions under a 450 – 600 m thick ice sheet between 42.000 – 12,400 years BP. The melting of glacier ice induced the formation of one or more subglacial meltwater lakes. Dropping overburden pressures lead to the eruption of vitric

tuff Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock co ...

. Over time this tuff accumulated and formed circular

tuff cone Volcanic cones are among the simplest volcanic landforms. They are built by ejecta from a volcanic vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, depending upon the nature and s ...

s, elongated tuff cones and ridges, volcanic edifices that were arranged "along 60 semi-parallel individual linear segments" (i.e. eruption fissures – in this case subglacial ones) "that vary in length between 0,25 and 1,5 km."Emily Constantine Mercurio: ''Processes, Products and Depositional Environments of Ice-Confined Basaltic Fissure Eruptions: A Case Study of the Sveifluháls Volcanic Complex, SW Iceland.'' University of Pittsburgh. (2011)
Retrieved 26 August 2020. In the following time, these edifices grew and developed further by subaqueous

density current Density (volumetric mass density or specific mass) is the ratio of a substance's mass to its volume. The symbol most often used for density is ''ρ'' (the lower case Greek language, Greek letter rho), although the Latin letter ''D'' (or ''d'') ...

s and resuspense resp. settling of the tuff within the meltwater lakes. This was facilitated by over steepening or retreat of the ice walls around the growing volcano.

Igneous Intrusion In geology, an igneous intrusion (or intrusive body or simply intrusion) 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 com ...

s into the piles of tuff also helped destabilizing them. The tuff cones and ridges grew and merged, but they also enclosed a source of

jökulhlaup A jökulhlaup ( ) (literally "glacial run") is a type of glacial outburst flood. It is an Icelandic term that has been adopted in glaciological terminology in many languages. It originally referred to the well-known subglacial outburst floo ...

in between them, inter-ridge meltwater catchments with volumes of up to 15 000 000 m3. In the whole, the eruptions of Sveifluháls may have produced 17.25 km3 of meltwater and a

DRE DRE may refer to: * ''Dre'' (album), 2010 by American rapper Soulja Boy Tell 'Em, 2010 * Dre (given name) **Dr. Dre Andre Romell Young (born February 18, 1965), known professionally as Dr. Dre, is an American rapper, record producer, recor ...

of 2,0 km3. In the end, the meltwater lakes drained and at least one of the eruption centers produced subaerial lava, which means that there is a

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 ...

component in the ridge, not all of it was produced by

subglacial eruption Subglacial eruptions, those of ice-covered volcanoes, result in the interaction of magma with ice and snow, leading to meltwater formation, jökulhlaups, and lahars. Flooding associated with meltwater is a significant hazard in some volcanic a ...

s. The eruption in the whole was probably similar to the Gjálp eruption within the

Grímsvötn Grímsvötn (; ''vötn'' = "waters", singular: ) is an active volcano with a (partially subglacial) fissure system located in Vatnajökull National Park, Iceland. The central volcano is completely subglacial and located under the northwestern side ...

Volcanic System in 1996.

Geothermal activity at Sveifluháls

Especially in two areas, geothermal activity at Sveifluháls is intense and connected to Krysuvík volcanic system. These are Seltún on the one hand, and the hills behind the farm and school of

on the other hand (so called ''Hveradalir'' ). Hot ground,

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 ...

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 and mud pots are to be found there. Measurements in Seltún even show a

thermal A thermal column (or thermal) is a rising mass of buoyant air, a convective current in the atmosphere, that transfers heat energy vertically. Thermals are created by the uneven heating of Earth's surface from solar radiation, and are an example ...

output of about 4 MW.

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 ...

and this heat lead to

precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, rain and snow mixed ("sleet" in Commonwe ...

of minerals like

hematite Hematite (), also spelled as haematite, is a common iron oxide compound with the formula, Fe2O3 and is widely found in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of . ...

goethite Goethite (, ) is a mineral of the diaspore group, consisting of iron(III) oxide-hydroxide, specifically the α- polymorph. It is found in soil and other low-temperature environments such as sediment. Goethite has been well known since ancient t ...

and different

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 ...

compounds.

Hiking

Many hiking trails lead up on Sveifluháls or are to be found in the vicinity. For example, there are trails up from Seltún at the southern end of the ridge to ''Arnarvatn'' and from there into the ''Móhálsadalur'' , or for hiking a round to ''Hetta'' , one of the southernmost summits of the long Sveifluháls ridge. There is also the possibility to hike from ''Vatnsskarð (Reykjanes)'' up on Sveifluháls and follow the ridge to the highest summit ''Stapatindur'' .Ari Trausti Guðmundsson, Pétur Þorsteinsson: ''Íslensk fjöll. Gönguleiðir á 152 tind.'' Reykjavík 2004, p. 266-267

External links

General information

*http://icelandicvolcanos.is/?volcano=KRI Krýsuvík. Catalogue of Icelandic Volcanoes. *https://volcano.si.edu/volcano.cfm?vn=371030 Krýsuvík. Global Volcanism Program. Smithsonian Institution.

Volcano monitoring

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

IMO. Aviation Color Code

Tourism

Sveifluháls. Visit Reykjanes. Official Website.

References

{{DEFAULTSORT:Sveifluhals Subglacial volcanoes of Iceland Southern Peninsula (Iceland) Krýsuvík Volcanic System Reykjanes Volcanic Belt Mountains of Iceland Hyaloclastite ridges