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 ...
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 ...
desert
A desert is a landscape where little precipitation occurs and, consequently, living conditions create unique biomes and ecosystems. The lack of vegetation exposes the unprotected surface of the ground to denudation. About one-third of the la ...
and close to
Askja
Askja () is an active volcano situated in a remote part of the central highlands of Iceland. The name Askja refers to a complex of nested calderas within the surrounding Dyngjufjöll mountains, which rise to , ''askja'' meaning ''box'' or ' ...
volcano. The desert is a large
lava
Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...
field originating from
eruption
A volcanic eruption occurs when material is expelled from a volcanic vent or fissure. Several types of volcanic eruptions have been distinguished by volcanologists. These are often named after famous volcanoes where that type of behavior has ...
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 in the area. Herðubreið was formed beneath the ice sheet that covered Iceland during the last
glacial period
A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate betw ...
.
Overview
This distinctive mountain has been known by its present name since at least 1300. Archive.org Due to the mountain's steep and unstable sides, the first definite ascent was in 1908 by Hans Reck and Sigurður Sumarliðason, despite centuries of knowledge of its existence.
The mountain is often referred to as "The Queen of Icelandic Mountains" by Icelanders due to its beautiful shape. It was voted in 2002 "Iceland’s favourite mountain".
Near the mountain lies an
oasis
In ecology, an oasis (; : oases ) is a fertile area of a desert or semi-desert environmentFjalla-Eyvindur, who lived there during the winter of 1774–1775.
In 2019, Herðubreið became a part of Vatnajökull National Park.
Geology
Herðubreið is a basaltic central subglacial volcano that formed during the last ice age under ice at least as thick as its current prominence of about . It is usually described as a composite volcano which is the same as 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 ...
. It is separate from the present potentially active fissure swarms and central volcanoes nearby and is believed to be inactive. Its original magma reservoirs are believed to have been at , and below the surface. There is in the upper crust, between deep, a broad belt of shallow seismicity extending from to the south of Herðubreið to the mountain itself due to plate boundary spreading. There is also deeper activity likely to be related to magmatic movements but perhaps this is related to the shallow volcano-tectonic seismic activity at the active
Askja
Askja () is an active volcano situated in a remote part of the central highlands of Iceland. The name Askja refers to a complex of nested calderas within the surrounding Dyngjufjöll mountains, which rise to , ''askja'' meaning ''box'' or ' ...
volcano nearby. Herðubreið is a classic tuya and was quickly recognised as such after the landform was described firstly as a subglacial volcanic construct in 1947.
The eruption sequence likely started before the glaciation of the last ice age south of Herðubreið in the ridge area called Herdubreidartögl with
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 basalt being erupted. Glaciation resulted in pressure on the magma reservoir that initially may have switched off further eruptive activity. In due course a second stage in the southern part of Herðubreið melted the ice with initial olivine tholeiite lava deposition under a lake that was followed by underwater
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 ...
mass flow deposits. This stage was not as confined by ice as the next stage and has evidence of a subaerial lava sheet, and had only moderately steep ice walls below this. As the ice sheet thickened further towards the glacial maximum of 12–15,000 years ago hyaloclastite, then pillow lavas under steep-sided hyaloclastite occurred. These built up until Herðubreið emerged above the lake surface, from a lake with almost vertical confining ice walls many about tall. If as happened in Herðubreið's case the eruption in its last stage became again sub-aerial with a lava cap and a spatter cone or crater vent.
Accordingly the southern portion of the plateau at the top of Herðubreiðar has a deep crater, which can contain a lake in summer. While by the end of glaciation, Herðubreiðar was extinct, volcanic activity resumed for a time at Herdubreidartögl to its south with fallout deposits and olivine tholeiitic lava flows in a much more spread out fashion.
See also
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Geography of Iceland
Iceland is an island country at the confluence of the Atlantic Ocean, North Atlantic and Arctic Ocean, Arctic oceans, east of Greenland and immediately south of the Arctic Circle, atop the constructive boundary of the northern Mid-Atlantic Ridg ...
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 ...
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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, ...