Brennisteinsfjöll (, "Sulfur mountains"
Brennisteinsfjöll. Detailed description. In: Catalogue of Icelandic Volcanoes. Retrieved 27 July 2020) is a minor Volcanism of Iceland, volcanic system, with crater rows and small

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 on the

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 ...

in southwest

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 ...

Geography

The mountain range is located at about from

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 ...

as well as

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 ...

and to the south of the cities on the Reykjanes peninsula of Southwest Iceland. Brennisteinfjöll is not high. The highest mountain is

Vífilsfell Vífilsfell () is a hyaloclastite ridge in southwestern Iceland (Weichselian). It is 655 m high and located west of Jósepsdalur valley on the volcanic plateau of Hellisheiði. It forms the northernmost offset of the Bláfjöll mountain massif ...

with 655 m.

Geology

Position within Iceland’s volcano-tectonic environment

In Iceland there are about 32 volcanic systems. Volcanic system means a volcano-tectonic fissure system and – very often a bigger volcano, a so-called

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 ...

which in most cases is a

stratovolcano A stratovolcano, also known as a composite volcano, is a typically conical volcano built up by many alternating layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with ...

and may contain a

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 ...

. Brennisteinsfjöll does not include such a central volcano. The existence of the fissure systems in Iceland is explained by its situation, located on top 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 ...

, a divergent plate boundary. There is most probably also a magmatic hot spot under the island which stands for increased magma production. Brennisteinsfjöll is one of four (some scientists say five) volcanic systems on the big peninsula of Reykjanes in Southwest Iceland, as such the system forms part of 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 ...

. These others are: Reykjanes volcanic system, around ''Gunnuhver'' at the tip of the peninsula, which mostly includes Svartsengi with the geothermal power station and the Blue Lagoon; to the east of the Reykjanes system is the

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

, including the geothermal areas around ''Seltún'',

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 Trölladyngja (Reykjanes) as well as lake Kleifarvatn; and to the northeast of the Brennisteinsfjöll lies the Hengill volcanic system which reaches out to the northeast over the lake

Þingvallavatn Þingvallavatn (, ), anglicised as Thingvallavatn, is a rift valley lake in southwestern Iceland. With a surface of 84 km2 it is the largest natural lake in Iceland. Its greatest depth is 114 m. At the northern shore of the lake, at Þingvellir ( ...

Þingvellir Þingvellir (, anglicised as ThingvellirThe spelling ''Pingvellir'' is sometimes seen, although the letter "p" is unrelated to the letter thorn (letter), "þ" (thorn), which is pronounced as "th".) was the site of the Althing, Alþing, the annual ...

.Thor Thordarson, Armann Hoskuldsson: Iceland. Classic geology of Europe 3. Harpenden 2002, p. 14 These volcanic systems are arranged en echelon and in a ca. 45° angle to the direction of

rifting 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 Fault (geology), downfaulted depression, called a graben, or more commonly ...

, scientists define this as an oblique arrangement. The volcanic systems of Reykjanes, Brennisteinsfjöll included, are stretched out in northeast-southwesterly direction over the rift on the peninsula.

General description of the Brennisteinsfjöll volcanic system

The volcanic system of Brennisteinsfjöll is long, has a width of about and covers about . Most to the south are the ''Stóra Eldborg'' crater row and to the north ''Nyðri Eldborg''.Daníel Páll Jónasson: Hraunflæði á höfuðborgarsvæðinu Saga hraunflæðis á svæðinu á nútíma og kortlagning mögulegra farvega til byggða. BS ritgerð. Leiðbeinandi:Ármann Höskuldsson. Háskóli Íslands, Reykjavík 2012. The volcanic system was the most productive of all the volcanic systems of the Reykjanes peninsula during the

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 ...

with 30-40 eruptions and around 10 since the settlement of Iceland in the 9th century.

Eruptions and current situation

One of the bigger lava flows of the system run south from Brennisteinsfjöll to the coast at Herdísarvík bay forming lava falls on their way. Previously it was thought that this lava flow had ceased before the settlement of Iceland (i.e. the end of the 8th century), but this is now thought that this was not the case as the coastal trail (now Route 42) was covered in lava at one stage. The last eruption in the Brennisteinsfjöll volcanic system was a VEI-2 eruption in 1341. It is a possible cause of St. Mary Magdalene’s flood 1342 in Central Europe und following bad years with Black Death to 1350. Brennisstein is the word for sulfur on Iceland, so great sulfur emissions with worldwide cooling for some years are possible and quite normal by this volcanic system. Most of its rocks consist 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 ...

Brennisteinsfjöll geothermal areas

There is a high temperature geothermal area in Brennisteinsfjöll, but it is rather remote, about southeast of Reykjavík in the inner part of the Reykjavík peninsula.Huang Maochang: Possible environmental impacts of drilling exploratory wells for geothermal development in the Brennisteinsfjöll area, SW-Iceland. United National University. Geothermal Training Programme. Reports 2001, no.5.
/ref> Fumaroles are to be found within an area of a few acres, and two more areas show signs of hydrothermal alteration. The surface conditions are complicated with a rough lava surface and the geothermal features which are located at a height of can only be reached on foot. The stratigraphy of the region includes hyaloclastite, older and younger lava flows. In a fault, not far from Grindarskörð , there are traces of a former geothermal area which is no more active.

Sulfur mining

As the name (Brennisteinsfjöll = Sulfur Mountains) suggests,

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 ...

is found here, though today in small amounts. But in the 19th century, a sulfur mine was run in the region by people from the United Kingdom. Mining was carried out just til the 1880s. The mine was situated in a lava slope. The sulfur “was deposited into holes and fractures in the lava and between lava layers”. It was therefore difficult to reach and mine. The miners had first to break up the lava to get to the sulfur. The current geothermal activity is above this area. The place of the former mine can be found by hiking the old trail Selvogsgata and the following the so-called Draugahlíðar between the lava and the slope. There are still some ruins of the former mine and traces of transportation paths.

Known mountains, craters and other volcanic landforms

Part of the Brennisteinsfjöll volcanic system are the Brennisteinsfjöll themselves (up on Hellisheiði), not really a mountain range, more some hills and crater rows, and the

Bláfjöll Bláfjöll (, "blue mountains") are a small mountain range in the southwest of Iceland on Reykjanes peninsula at about 30 km from Reykjavík. They form sort of a double mountain massif to the west and in the east of JósepsdalurÞór Vigf ...

mountain massif. The system includes two

es, Heiðin há and

Leitin Leitin () is a small shield volcano in the southwest of Iceland. Name Leitin ("the hills") is sometimes also called Leiti ("hills") or Leitahraun after its eruption products (“the lava of Leiti”). Geography The lava shield is located ...

. Among the many smaller

subglacial mound A subglacial mound is a type of subglacial volcano formed when lava erupts beneath a thick glacier or ice sheet. The magma forming these volcanoes was not hot enough to melt a vertical pipe right through the overlying glacial ice, instead forming ...

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, craters and eruptive vents are Stóra-Kóngsfell, Drottning, the Þríhnúkagígar crater trio – now famous because it is possible to see a magmatic feeder system from the inside -, and some craters named Eldborg (e.g.

Eldborg í Bláfjöllum The volcanic cone of Eldborg í Bláfjöllum () is to be found at about 2 km from the skiing area in Bláfjöll, i.e. at about 25 km from Reykjavík, in Iceland.Ísland Vegaatlas. Reykjavík 2006, p.1 Scoria cones Eldborg í Bláfjö ...

and Stóra-Eldborg undir Geitahlíð). The rootless cones of Rauðhólar near Reykjavík are also connected to a lava flow from this volcanic system.

Nature protection in Brennisteinsfjöll

Some protected areas are to be found in the region of Brennisteinsfjöll. These are Herdísarvík Nature Reserve, Reykjanes Country Park,

Country Park and the two Natural Monuments ''Eldborgir undir Geitahlíð'' and ''Eldborg í Bláfjöllum''.Suðvesturland. Friðlýst Svæði. Umhverfisstofnun. Government of Iceland.(in Icelandic

External links

Volcanism of Brennisteinsfjöll

Brennsteinsfjöll
in the

Catalogue of Icelandic Volcanoes The Catalogue of Icelandic Volcanoes (CIV) is a web resource that was created to serve as an official source of information about potentially active volcanoes monitored by Iceland. The creation of the website followed the disruptive 2010 eruption ...

*
Huang Maochang: Possible environmental impacts of drilling exploratory wells for geothermal development in the Brennisteinsfjöll area, SW-Iceland. United National University. Geothermal Training Programme. Reports 2001, no.5.

Volcano monitoring

* https://en.vedur.is/earthquakes-and-volcanism/earthquakes/reykjanespeninsula/ Icelandic Met Office (IMO). Earthquake Monitoring. Reykjanes Peninsula *https://en.vedur.is/earthquakes-and-volcanism/volcanic-eruptions/ IMO. Aviation Color Code

References

{{DEFAULTSORT:Brennisteinsfjoll Volcanoes of Iceland VEI-2 volcanoes Southern Peninsula (Iceland) Volcanic systems of Iceland Reykjanes Volcanic Belt Brennisteinsfjöll Volcanic System