Postglacial eruptive history of the Askja region, North Iceland

• Published in: Bulletin of Volcanology
• Main Authors: Hartley, Margaret E., Thordarson, Thorvaldur, de Joux, Alexandra
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2016
• Subjects: Askja; Vatnaöldur; Hekla; Iceland
• Online Access: https://research.manchester.ac.uk/en/publications/0fddc830-45dc-468d-8aae-c051e73589b1; https://doi.org/10.1007/s00445-016-1022-7

Temporal variations in magma discharge rates on Iceland’s neovolcanic rift zones have been associated with deglaciation. We have used tephrochronological and stratigraphic dating of 175 separate eruptive units to estimate volumetric output and reconstruct eruption rates in the Askja region over the postglacial period. We have identified 14 tephra layers that can be used as time marker horizons in the near vicinity of Askja, including the Vatnaöldur (871 ± 2 AD) tephra which has not previously been reported in surface cover profiles in this region. Our improved tephrochronological resolution indicates that, over the past c. 1,500 years, Askja has been significantly more active than has previously been recognised. A minimum of 39 km3 of basaltic magma has been erupted at Askja since the area became ice-free at around 10.3 ka. The absence of the 7.2 ka Hekla 5 tephra from the Askja region suggests that all postglacial lavas now exposed at the surface are younger than 7.2 ka. Time-averaged magma discharge rates at Askja were highest between 7.2 and 4.3 ka. However, the available tephrochronological resolution is not sufficient to resolve any peak in volcanic activity following deglaciation.