Prestahnúkur
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The peak Prestahnúkur () with a height of , is in the Western Volcanic Zone to the west of the
Highlands of Iceland The Highland (Icelandic language, Icelandic: ''Hálendið)'' or The Central Highland is an area that comprises much of the interior land of Iceland. The Highland is situated above and is mostly uninhabitable. The soil is primarily volcanic as ...
to the west of
Langjökull Langjökull (, Icelandic for "long glacier") is the second largest ice cap in Iceland (), after Vatnajökull. It is situated in the west of the Icelandic interior or Highlands of Iceland and can be seen clearly from Haukadalur. It covers the ...
glacier, or to be more specific, to the west of
Geitlandsjökull Geitlandsjökull () is a lateral glacier of Langjökull, with a flowshed of from the second largest ice cap in Iceland at , in the west of Iceland. It has also been used as the name for the substantial Langjökull ice cap, as has the name Suðurj ...
glacier, a part of the Langjökull. The
volcano A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most oft ...
Prestahnúkur includes the terrain under the Geitlandsjökull glacier continuous to the peak and also includes fissure fields to its north and south.


The volcanic system

The
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 ...
Prestahnúkur consists of a
rhyolite Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture (geology), texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained matri ...
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 ...
that was formed entirely under ice, and has been dated as 89 ± 24 , but another dating is about 60 ka. Two vents have been found. At the base of the northern flank is a geothermal area, with the rhyolite and hot springs suggesting that a long-lived magma chamber is or has been present. There has been intermittent seismic activity, mostly in an area about wide centred at the central volcano, but as no dyke intrusions have been observed, so it is unproven that the volcano is active. In 2009 geologists in their research of
earthquake An earthquakealso called a quake, tremor, or tembloris the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they ...
events in the area showed that volcanic fissures lie in direction southwest–northeast and reach under the glaciers Þórisjökull and
Geitlandsjökull Geitlandsjökull () is a lateral glacier of Langjökull, with a flowshed of from the second largest ice cap in Iceland at , in the west of Iceland. It has also been used as the name for the substantial Langjökull ice cap, as has the name Suðurj ...
-
Langjökull Langjökull (, Icelandic for "long glacier") is the second largest ice cap in Iceland (), after Vatnajökull. It is situated in the west of the Icelandic interior or Highlands of Iceland and can be seen clearly from Haukadalur. It covers the ...
. The Prestahnúkur fissure swarm has subsequently been defined as extending both to the north and south of the central volcano with a total length between and width up to . To the north the Hallmundarhraun lava flow is believed to have most likely erupted sometime between 782 and 860 CE and extends well beyond Eiríksjökull. The Jökulkrókur lava to its west is between 1800 and 4500 years and one of the Geitlandshraun lava flows to its south-east has been dated to 8900 years BP. The other Geitlandshraun lava flow is under ice just north of the central volcano and is undated, but older. The Ok shield volcano rises to a height of to the east-nor-east of the central volcano. To the south-east of the central volcano some of the fissure swarm is now covered by lava from the
Skjaldbreiður Skjaldbreiður (, "broad shield") is an Icelandic lava shield formed in a huge and quite protracted eruption series from about roughly 9,500 years ago. The extensive lava fields which were produced by this eruption, flowed southwards, and f ...
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 ...
which is in a neighbouring volcanic system. The southern extent of the fissure swarm is unclear and may overlap with that of the
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. Intraglacial volcanic formations in the fissure swarm include tuyas produced by fissure eruptions through single vents and tindars. Apart from the Hrúðurkarlar tindars which cut obliquely across the swarm, the tindars parallel the fissure swarm at a strike of about 30°.


Rock Geology

The central volcanoes rhyolite has for Iceland a high silica content of about 77%, and must have come from a single batch of magma over a relatively short time span of less than 20 years. It was for some time a popular exploited construction material, partly for export. But the mine has been closed. The fissure swarm lavas are
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 ...
ic
olivine The mineral olivine () is a magnesium iron Silicate minerals, silicate with the chemical formula . It is a type of Nesosilicates, nesosilicate or orthosilicate. The primary component of the Earth's upper mantle (Earth), upper mantle, it is a com ...
tholeiite The tholeiitic magma series () is one of two main magma series in subalkaline igneous rocks, the other being the Calc-alkaline magma series, calc-alkaline series. A magma series is a chemically distinct range of magma compositions that describes ...
.


The name

The name means "peak of the priests". The origin of the name was an expedition of two priests into the highlands in the 17th century. It was seen as quite an enterprise at the time when they went into this region. They explored especially a valley behind the Þórisjökull called Þórisdalur, which had a bad reputation in sagas and folk stories because it was believed to be haunted by ghosts and that lawless people would be living there. As is clear today, they found nothing of the sort, but they were regarded as heroes when they came back from this expedition.


Highland Road Kaldidalur and mountaineering

The highland road Kaldadalsvegur is situated not far from the mountain and it is possible to access the mountain by a bad jeep track and climb it.


See also

* List of mountains in Iceland *
Volcanism of Iceland :''The volcano system in Iceland that started activity on August 17, 2014, and ended on February 27, 2015, is Bárðarbunga.'' :''The volcano in Iceland that erupted in May 2011 is Grímsvötn.'' Iceland experiences frequent volcanic activity, ...
**
List of volcanic eruptions in Iceland This is an incomplete list of volcanic eruptions in Iceland. Please see External links below for databases of Icelandic eruptions which include over 530 events. ''For latest information about the current/ongoing series of eruptions near Grindav ...
**
List of volcanoes in Iceland There are too many presumed extinct or now inactive volcanic features to list all of these below, so most monogenetic volcanoes can not be mentioned individually. This list of volcanoes in Iceland only includes major active and dormant volcano, ...


Notes


References


Sources

* * * *


External links


Prestahnúkur
in the Catalogue of Icelandic Volcanoes
Icelandic Meteorological Institute, 2009, Icelandic with English summary and maps

Photo: with a jeep onto the mountain
* {{DEFAULTSORT:Prestahnukur Central volcanoes of Iceland Active volcanoes West Volcanic Zone of Iceland Borgarbyggð Volcanic systems of Iceland