Jökull - 01.01.2010, Blaðsíða 112

Hjartardóttir et al.
Figure 9. A part of the Kerlingar fault, viewed towards the west. Yellow dashed lines denote the top and bottom
of the fault scarp. The mountaintop is Mt. Hólskerling. – Horft í vesturátt að Kerlingamisgenginu. Efri og
neðri mörk misgengisins eru táknuð með brotnum gulum línum. Fjallstindurinn í baksýn kallast Hólskerling.
The formation of the fault
We consider three possible explanations for the exis-
tence of the Kerlingar fault:
1) That the fault was formed in a rifting event re-
lated to its location at the end of the Möðrudalur area,
which is in the continuation of the Kverkfjöll fissure
swarm.
2) That the fault was formed by stress transfer in re-
lation to the activity of the Húsavík transform fault
(Figure 1).
3) That the fault formed or was reactivated by isostatic
response due to rapid crustal deloading during the last
deglaciation.
The first point is supported by the location of
the fault in the continuation of the Kverkfjöll fis-
sure swarm, if we assume that the hyaloclastite for-
mations that form an arc-shaped continuation of the
Kverkfjöll fissure swarm are a part of the fissure
swarm (Figure 1). However, the fissure swarm (as
indicated by high density of tectonic fractures active
in the Holocene), ends ∼50 km south of the area,
while the Kerlingar fault area is mostly characterized
by hyaloclastite ridges, indicating subglacial Pleis-
tocene fissure eruptions (Kjartansson 1943). During
the Holocene, this area has therefore experienced few
or no rifting events. Also, the fault is not oriented
parallel with the most recent, sharp and narrow hyalo-
clastite ridges in the area, which are parallel with the
NVZ fissure swarms to the west. This suggests that
the fault was not formed in a typical rifting event.
Regarding the second point, the Kerlingar fault is
in the direct continuation of the Húsavík transform
fault (Figure 1), and it has been shown that the orienta-
tion of fractures in fissure swarms can change abruptly
where a fissure swarm intersects with a transform fault
(Gudmundsson et al. 1993). In a similar manner, the
unusual NW orientation of the Kerlingar fault could
be associated with the Húsavík transform fault. How-
ever, we consider such a link unlikely in the case of
the Kerlingar fault, mainly for two reasons. Firstly,
for this mechanism to be true, we would have to as-
sume that the Húsavík fault extends all the way to the
112 JÖKULL No. 60