Volcanism in Iceland in historical time: Volcano types, eruption styles and eruptive history
Introduction
Volcanism in Iceland is diverse for an oceanic island and has featured nearly all volcano types and eruption styles known on Earth (Thorarinsson and Sæmundsson, 1979, Thorarinsson, 1981). The volcano types range from archetypal mafic lava shields to classical conical-shape stratovolcanoes, whereas the styles of volcanic activity span the spectrum of effusive as well as phreatomagmatic and magmatic explosive eruptions in the settings of subaerial to subglacial and submarine environments. Although volcanism is typified by effusive basalt eruptions, it is also characterized by a range of explosive styles that includes felsic eruptions of subplinian and Plinian intensities as well as the renowned mafic subglacial phreatomagmatic eruptions. The effects of many Icelandic eruptions have been felt on a hemispheric scale and the very largest ones may have had global impact.
Just over 25 years ago, Thorarinsson and Sæmundsson (1979), published a decisive paper titled “Volcanic activity in historical times”, outlining the contemporary understanding of Icelandic volcanoes. Since then significant advances have been made and it is time to present a new review of the volcanic activity in Iceland in historical times, which is the principal objective of this paper.
Section snippets
Geologic setting
The Iceland basalt plateau is situated at the junction of two large submarine physiographic structures, the Mid-Atlantic Ridge and the Greenland–Iceland–Faeroe Ridge (Fig. 1). It rises more than 3000 m above the surrounding sea floor, has crustal thickness of 10–40 km and covers about 350,000 km2 (e.g. Gudmundsson, 2000 and references therein). About 30% of this area (∼103,000 km2) is above sea level, the remainder forms the 50–200 km wide shelf around the island. The construction of the Iceland
Volcano types and forms
The term volcano encompasses a wide range of structures that are constructed around the vent(s) by the volcanic activity, whether they are formed by single (monogenetic) or multiple (polygenetic) eruptions (Macdonald, 1972, Cas and Wright, 1987, Francis and Oppenheimer, 2004). The overall architecture of a volcano is primarily determined by the type of magma erupted, the habitual eruption behaviour, the shape of the vent system and the environmental setting (i.e. subaerial, subglacial,
Distribution and frequency of historical eruptions
Volcanic activity in Iceland in historical time (i.e. over the last 1100 years) is a direct continuation of the prehistoric Holocene activity and generally confined to the same volcanic regions. A total of 16 volcanic systems have been volcanically active during this period. Of 9 volcanic systems on the RVZ–WVZ sector of the axial zone (Fig. 2), 4 have erupted in the last 1100 years. Those are the, Reykjanes–Svartsengi, Krýsuvík, Brennisteinsfjöll, and Langjökull systems on the WVZ–RVZ (Fig. 3;
Summary
- 1.
Holocene volcanism in Iceland is confined to the neovolcanic zones, which are represented by discrete 15–50 km wide volcanic zones and belts that collectively cover about one-third of Iceland. Volcanic systems are the principal structure of the volcanic zones and in total there are 30 active systems in Iceland. The volcanic systems are comprised of a fissure swarm or a central volcano or both. A fissure swarm and a central volcano coexist on 12 systems, whereas 7 are only comprised of a central
Acknowledgements
We are grateful to Ágúst Gudmundsson and Magnús T. Gudmundsson for constructive reviews and suggestions, which resulted in significant improvements on the initial draft of this manuscript.
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