Ljósufjöll
| Ljósufjöll | |
|---|---|
 Grábrók [ˈkrauːˌprouːk] crater | |
| Highest point | |
| Elevation | 1,063 m (3,488 ft)[1] |
| Geography | |
 Approximate map of central volcanoes and their fissure fields (paler shading) in the Snæfellsnes volcanic belt: Ljósufjöll Mouse over is enabled on clicking the map and this will allow identification of features (yellow) mentioned in the text on this page.[1] | |
| Location | Iceland |
| Geology | |
| Mountain type | Fissure vents |
| Last eruption | 960 CE ± 10 years[2] |
Ljósufjöll (Icelandic pronunciation: [ˈljouːsʏˌfjœtl̥] ⓘ) is a fissure vent system and central volcano on the Snæfellsnes Peninsula in Iceland. The name derives from the central volcano and translates into English as "Mountains of the Light".
Geography
[edit]The volcanic system has a length of about 90 km (56 mi) and a maximum width at its eastern end of about 20 km (12 mi).[1] The north-western part of the Ljósufjöll volcanic system has hyaloclastite hills and lava flows about 3–6 km (1.9–3.7 mi) wide.[1] This progresses into the ridge like central volcano with its highest peak of 1,063 m (3,488 ft).[1] The fissure swarm widens to the south-east and extends towards the Haffjarðará river and the town of Bifröst at the eastern base of the peninsula.
Geology
[edit]The volcanic system is part of the Snæfellsnes volcanic belt (zone). This is an intra-plate volcanic zone less than 3.3 million years old, erupting through 25–29 km (16–18 mi) of crust at Ljósufjöll.[3] The belt has relatively low geothermal gradients for Iceland at about 40–60 °C/km (120–170 °F/mi) and erupts alkalic to transitional basalts, [3] with the Ljósufjöll system tending to be less alkalotic.[1]
The Ljósufjöll volcanic system's oldest rocks are about 780,000 years old.[1] It contains cinder cones and is the only system on the peninsula that has erupted in recorded history, in 960 CE ± 10.[2] This produced from a single crater a 13 km2 (5.0 sq mi) lava flow called Rauðhálsahraun [ˈrœyðˌhaulsaˌr̥œyːn], and a tephra scoria layer that covered about 50 km2 (19 sq mi).[1] In this region of the system to the east, the younger basaltic formations often do not entirely cover the older Neogene basement rocks.[1]
The central volcano in the system is highly silicic with the largest Quaternary rhyolitic 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.[1] The fissure swarm has produced about 17 basaltic lava flows during the Holocene with the largest covering 33 km2 (13 sq mi).[3] The most studied eruption of the system is one that occurred about 4000 years ago, called the Berserkjahraun [ˈpɛrˌsɛr̥caˌr̥œyːn] 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 [ˈkʰɔtˌr̥œynsˌkʰuːla], Smáhraunskúlur [ˈsmauːˌr̥œynsˌkʰuːlʏr̥], Gráakúla [ˈkrauːaˌkʰuːla] and Rauðakúla [ˈrœyːðaˌkʰuːla].[3] 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.[3] The studies done have included the Vatnafell [ˈvahtnaˌfɛtl̥] tuya, which is between the western portion of the definitely assigned Ljósufjöll volcanic system and the Helgrindur volcanic system and might belong to either system.[4]
Activity
[edit]Seismic activity increased at a depth of between 15 and 20 km (9.3 and 12.4 mi) near Grjótárvatn [ˈkrjouːtˌaurˌvahtn̥], 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.[5]
See also
[edit]References
[edit]- ^ a b c d e f g h i j Jóhannesson, Haukur (2016). "Catalogue of Icelandic Volcanoes - Ljósufjöll:Map Layers". Icelandic Meteorological Office, Institute of Earth Sciences at the University of Iceland, Civil Protection Department of the National Commissioner of the Iceland Police. Retrieved 24 February 2024.
- ^ a b "Ljósufjöll". Global Volcanism Program. Smithsonian Institution. Retrieved 2021-06-25.
- ^ a b c d e Kahl, M.; Bali, E.; Guðfinnsson, G.H.; Neave, D.A.; Ubide, T.; van der Meer, Q.H.A.; Matthews, S. (2021). "Conditions and Dynamics of Magma Storage in the Snæfellsnes Volcanic Zone, Western Iceland: Insights from the Búðahraun and Berserkjahraun Eruptions". Journal of Petrology. 62 (9). doi:10.1093/petrology/egab054.: Geological Context:Geology of the Snæfellsnes volcanic zone, Western Iceland
- ^ Burney, D.; Peate, D.W.; Riishuus, M.S.; Ukstins, I.A. (2020). "Reconstructing the plumbing system of an off-rift primitive alkaline tuya (Vatnafell, Iceland) using geothermobarometry and CSDs". Journal of Volcanology and Geothermal Research. 399: 106914. Bibcode:2020JVGR..39906914B. doi:10.1016/j.jvolgeores.2020.106914.
- ^ "Seismic activity in Grjótárvatn has increased in the last months". Icelandic Meteorological Office. 20 December 2024. Retrieved 21 December 2024.