Jökull - 01.01.2015, Page 3

Structure and tectonic position of the Eyjafjallajökull volcano, S-Iceland
Figure 2. Map of the volcanoes of the South Iceland flank zone, showing their relationship to the tectonic grain
of the plate boundary zones (South Iceland Seismic Zone, SISZ, and the Eastern Volcanic Zone, EVZ) and the
topography off shore. Bathymetry contours are in metres. Fractures of the SISZ are after Einarsson (2010). –
Megineldstöðvar í jaðargosbelti Suðurlands og tengsl þeirra við sprungustefnur á landi og landslag á hafsbotni.
Dýptartölur eru í metrum. Sprungur á skjálftasvæði Suðurlands (SISZ) eru samkvæmt Einarsson (2010).
both zones, with the EVZ accommodating 40–100%
of the relative motion between the North America and
Eurasia plates (LaFemina et al., 2005). The spread-
ing rate decreases southwards and active rifting ter-
minates south of the Torfajökull volcano (Figure 2).
In the WVZ, on the other hand, the spreading rate de-
creases northwards, which leads to a slow rotation of
the Hreppar Microplate (Einarsson, 2008).
The Eyjafjallajökull volcano, that became the fo-
cus of attention during its 2010 eruptions, is one of
several volcanoes at the tip of the propagating rift. In
this paper we describe the structure of this volcanic
system, and clarify its position within this tectonic
framework and its relation to neighbouring volcanoes.
PLATE TECTONIC CONTEXT OF THE
VOLCANO
The volcanoes of the South Iceland Volcanic Flank
Zone, Hekla, Torfajökull, Vatnafjöll, Tindfjallajökull,
Katla, Eyjafjallajökull and Vestmannaeyjar (Figure
2), all have very different appearance and behaviour.
This probably reflects their different distance to the
plate boundary, difference in crustal structure, and dif-
ferent age and degree of maturity. Hekla and Torfa-
jökull are located at the junction of the EVZ with
the transform zone of South Iceland (SISZ). Vestman-
naeyjar are located farthest to the SW and are the
youngest member of the family, in a state of birth.
The alkalinity of the products of these seven volcanic
JÖKULL No. 65, 2015 3