Helgafell () is a mountain on

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 ...

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 ...

. The height of the mountain is 338 m.

Name

Many mountains in Iceland bear the name of ''Helgafell''. It means “''holy mountain''” and is thought that in the

Viking Vikings were seafaring people originally from Scandinavia (present-day Denmark, Norway, and Sweden), who from the late 8th to the late 11th centuries raided, pirated, traded, and settled throughout parts of Europe.Roesdahl, pp. 9� ...

era, these mountains played a special – if unknown – role in the worship of their gods.Ari Trausti Guðmundsson, Pétur Þorsteinsson: Íslensk fjöll. Gönguleiðir á 152 tind. Reykjavík 2004, p. 98 An architect from Reykjavík measured out the positions of the very old

cairn A cairn is a human-made pile (or stack) of stones raised for a purpose, usually as a marker or as a burial mound. The word ''cairn'' comes from the (plural ). Cairns have been and are used for a broad variety of purposes. In prehistory, t ...

on top of Helgafell as well as the cairns of two other mountains in the vicinity and came to the conclusion that by using the positions of the sun as well as the shades of the cairns, the Vikings had constructed a calendar.

Subglacial volcano

The mountain is a

hyaloclastite ridge 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 margi ...

formed during the Weichselian glaciation of the

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 ...

epoch. Erica A. Massey: A Comparative Study of Glaciovolcanic Palagonitization of Tholeitic and Alkaline Sideromelane in Helgafell, Icland, and Wells Gray-Clearwater Volcanic Filed, BC, Canada. B.Sc., The University of British Columbia, 2014
/ref> Its typical form shows well as there is not much vegetation on its slopes. Helgafell is located in a tectonically and volcanically active region: the last eruption on Reykjanes peninsula in February 2024. The mountain is situated within the area of the

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 ...

. It “is thought to have formed in a single subglacial

fissure eruption A fissure vent, also known as a volcanic fissure, eruption fissure or simply a fissure, is a linear volcanic vent through which lava erupts, usually without any explosive activity. The vent is often a few metres wide and may be many kilom ...

under at least 500 m of glacial ice“. The original ridge was about 2km long. 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 ...

lava flows, also from the neighbouring

Brennisteinsfjöll Brennisteinsfjöll (, "Sulfur mountains"
Brennisteinsfjöll. Detailed description. In: Catalogue of Icelandic Volcano ...

volcanic system, surrounded the mountain later. Helgafell is made mostly from

palagonite Palagonite is an alteration product from the interaction of water with volcanic glass of chemical composition similar to basalt. Palagonite can also result from the interaction between water and basalt melt. The water flashes to steam on contact ...

, i.e. palagonitized

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, ...

dikes Dyke or dike may refer to: General uses * Dyke (slang), a slang word meaning "lesbian" * Dike (geology), formations of magma or sediment that cut through and across the layering of adjacent rocks * Dike (mythology), ''Dikē'', the Greek goddess ...

and a small amount 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 ...

Formation of Helgafell

Helgafell is most probably a monogenetic

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 ...

, because no traces of subaerial eruptions were found on its slopes. H.H.Schopka, M.T.Gudmundsson, H.Tuffen: The formation of Helgafell, southwest Iceland, a monogenetic subglacial hyaloclastite ridge: Sedimentology, hydrology and volcano–ice interaction. Journal of Volcanology and Geothermal Research 152 (2006) 359–377. Retrieved 9 August 2020.
/ref> The ice sheet under which the Helgafell eruptions took place, was about 500 m thick at time of eruption. In the beginning a fissure opened at right angles to the ice flow, which was from the southeast to the northwest. It was about 15 km from the glacier snout. There is a big

terminal moraine A terminal moraine, also called an end moraine, is a type of moraine that forms at the terminal (edge) of a glacier, marking its maximum advance. At this point, debris that has accumulated by plucking and abrasion, has been pushed by the front e ...

at the coast at

Álftanes Álftanes () is the name of a town and a collection of small peninsulas in Iceland. It means ''swan peninsula''. The best known of these peninsulas extrudes from the eastern part of Reykjanes with the town of the same name in the Capital Region ...

. Rapid ice melting was the consequence of

explosive eruption In volcanology, an explosive eruption is a volcanic eruption of the most violent type. A notable example is the 1980 eruption of Mount St. Helens. Such eruptions result when sufficient gas has dissolved under pressure within a Viscosity, viscous ...

and therefore

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 ...

fragmentation from the start of the eruption. At Helgafell next an edifice was formed about 300 m high in an ice vault, meltwater drained away very fast through subglacial channels so that the explosive activity continued to the end, which seems to have been after some days. This explains the fact, that Helgafell is next to overall made from

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 ...

, whereas most other researched smaller subglacial volcanoes showed a basis of

pillow lavas 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 ...

. Of these and some small

intrusions In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of Intrusive rock, intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety o ...

, the researchers just found minimal quantities.

Aeolian erosion Aeolian processes, also spelled eolian, pertain to wind activity in the study of geology and weather and specifically to the wind's ability to shape the surface of the Earth (or other planets). Winds may erode, transport, and deposit materials ...

removed part of the summit in the

and other parts of the mountain slumped. The

lava field A lava field, sometimes called a lava bed, is a large, mostly flat area of lava flows. Such features are generally composed of highly fluid basalt lava, and can extend for tens or hundreds of kilometers across the underlying terrain. Morp ...

s surrounding Helgafell today are about 40–80 m in thickness as gravity surveys showed.

Hut Kaldársel and river Kaldá

Kaldársel is a hut run by an Icelandic youth organization (KFUM) where hikers also are welcome. It is possible to get by car along ''Kaldárselsvegur'' from

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 ...

up to a parking lot in the vicinity. The hut has its name from ''Kaldá'', a small

intermittent river Intermittent, temporary or seasonal rivers or streams cease to flow every year or at least twice every five years. Such rivers drain large arid and semi-arid areas, covering approximately a third of the Earth's surface. The extent of tempora ...

nearby. The area around it is fenced in, because it is part of the drinking water resources of the neighboring towns. Folk tales “explain” the disappearances of the river: Once a man could use witch craft, but lost two of his sons who drowned in the river. He shall then have used some of his tricks so that the river had to go underground.

Hiking

The mountain is relatively close to

as well as to

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 ...

. Many hiking trails are in its vicinity and also up on the mountain, so that it is a very popular hiking area. There are also two long hiking trails at the base of the mountain: the ''Reykjavegur'' which makes it possible to hike all the length of Reykjanes Peninsula (about 120 km) and the old trail of Selvogsgata.See t.d. map p. 11 in: Reynir Ingibjartsson: 25 Gönguleiðir á Reykjanesskaga. Náttúrann við Bæjarveggin. Reykjavík It is a rather easy hike up on the mountain and even easier to hike around it or just up on Valahnúkarskarð between Helgafell and Valahnúkar (another subglacial mound from the Pleistocene as well as the mountain Húsfell in a certain distance).

External links

Still another hike: Helgafell – Valahnúkar – Húsfell Erica A. Massey: A Comparative Study of Glaciovolcanic Palagonitization of Tholeitic and Alkaline Sideromelane in Helgafell, Icland, and Wells Gray-Clearwater Volcanic Filed, BC, Canada. B.Sc., The University of British Columbia, 2014

References

{{reflist Mountains of Iceland Volcanoes of Iceland Southern Peninsula (Iceland) Reykjanes Volcanic Belt Hyaloclastite ridges Monogenetic volcanoes