Ljósufjöll

Geography

The volcanic system has a length of about 90 km and a maximum width at its eastern end of about 20 km. The north-western part of the Ljósufjöll volcanic system has hyaloclastite hills and lava flows about 3 - wide. This progresses into the ridge like central volcano with its highest peak of 1063 m. 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

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 – of crust at Ljósufjöll. The belt has relatively low geothermal gradients for Iceland at about 40 – and erupts alkalic to transitional basalts, 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 cones 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 13 km2 lava flow called Rauðhálsahraun , and a tephra scoria layer that covered about 50 km2. In this region of the system to the east, the younger basaltic formations often do not entirely cover the older Neogene basement rocks.

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.

Activity

Seismic activity increased at a depth of between 15 and 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

References

1. {{cite gvp
2. (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.
3. (2021). "Conditions and Dynamics of Magma Storage in the Snæfellsnes Volcanic Zone, Western Iceland: Insights from the Búðahraun and Berserkjahraun Eruptions". Journal of Petrology.
4. (2020). "Reconstructing the plumbing system of an off-rift primitive alkaline tuya (Vatnafell, Iceland) using geothermobarometry and CSDs". Journal of Volcanology and Geothermal Research.
5. (20 December 2024). "Seismic activity in Grjótárvatn has increased in the last months". [[Icelandic Meteorological Office]].