Ljósufjöll () is a

fissure vent 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 kilo ...

system and

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 ...

on the

Snæfellsnes The Snæfellsnes () is a peninsula situated to the west of Borgarfjörður, in western Iceland. The peninsula has a volcanic origin having the Snæfellsnes volcanic belt down its centre, and the Snæfellsjökull volcano A volcano is com ...

Peninsula in Iceland. The name derives from the central volcano and translates into English as "Mountains of the Light".

Geography

The volcanic system has a length of about and a maximum width at its eastern end of about . The north-western part of the Ljósufjöll volcanic system has

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 ...

hills and

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 ...

flows about wide. This progresses into the ridge like central volcano with its highest peak of . The fissure swarm widens to the south-east and extends towards the Haffjarðará river and the town of

Bifröst In Norse mythology, Bifröst (modern Icelandic: Bifröst ; from Old Norse: /ˈbiv.rɔst/), also called Bilröst and often anglicized as Bifrost, is a burning rainbow bridge that reaches between Midgard (Earth) and Asgard, the realm of the gods. ...

at the eastern base of the peninsula.

Geology

The volcanic system is part of the

Snæfellsnes volcanic belt The geological deformation of Iceland is the way that the rocks of the island of Iceland are changing due to tectonic forces. The geological deformation help to explain the location of earthquakes, volcanoes, fissures, and the shape of the island. ...

(zone). This is an intra-plate volcanic zone less than 3.3 million years old, erupting through of crust at Ljósufjöll. The belt has relatively low geothermal gradients for Iceland at about and erupts alkalic to transitional

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 ...

s, with the Ljósufjöll system tending to be less alkalotic. The Ljósufjöll volcanic system's oldest rocks are about 780,000 years old. It contains

cinder cone A cinder cone or scoria cone is a steep, volcanic cone, conical landform of loose pyroclastic rock, pyroclastic fragments, such as volcanic ash, clinkers, or scoria that has been built around a volcanic vent. The pyroclastic fragments are forme ...

s and is the only system on the peninsula that has erupted in recorded history, in 960 CE ± 10. This produced from a single crater a lava flow called Rauðhálsahraun , and a

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, ...

scoria layer that covered about . In this region of the system to the east, the younger basaltic formations often do not entirely cover the older

Neogene The Neogene ( ,) is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period million years ago ( Mya) to the beginning of the present Quaternary Period million years ago. It is the second period of th ...

basement rocks. The central volcano in the system is highly

silicic Silicic is an adjective to describe magma or igneous rock rich in silica. The amount of silica that constitutes a silicic rock is usually defined as at least 63 percent. Granite and rhyolite are the most common silicic rocks. Silicic is the g ...

with the largest

Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS), as well as the current and most recent of the twelve periods of the ...

rhyolitic Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals ( phenocrysts) in an otherwise fine-grained groundmass. The miner ...

outcrop in the Snæfellsnes volcanic belt, which causes a light coloration to the volcanoes rocks. The central volcano has erupted twice in the last 4000 years. The fissure swarm has produced about 17 basaltic lava flows 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 the largest covering . The most studied eruption of the system is one that occurred about 4000 years ago, called the Berserkjahraun eruption, near the north-west coast of the Snæfellsnes Peninsula. The four craters are in a west to east alignment and are known as Kothraunskúla , Smáhraunskúlur , Gráakúla and Rauðakúla . This must have had magma that evolved in two different storage zones, presumably one in the lower crust and one in the upper-mid-crust so as to be consistent with other findings in the Snæfellsnes volcanic belt. The studies done have included the Vatnafell

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 ...

, which is between the western portion of the definitely assigned Ljósufjöll volcanic system and the Helgrindur volcanic system and might belong to either system.

Activity

Seismic activity increased at a depth of between near Grjótárvatn , which is within the area of the volcanic system, in late 2024. This could be due to magma accumulation at depth or intra-plate tectonic movement.

References

External links

Ljósufjöll
in the Catalogue of Icelandic Volcanoes {{DEFAULTSORT:Ljosufjoll Volcanoes of Iceland Fissure vents VEI-3 volcanoes Active volcanoes Snæfellsnes Volcanic systems of Iceland Central volcanoes of Iceland

Geography

Geology

Activity

See also

References

External links