Jökull - 01.01.2015, Side 62

Sigurðardóttir et al.
Vatnajökull
ice cap
Landbrot
lava field
Meðalland
lava field
Álftaver
lava field
Mýrdalsjökull
ice cap
Katla
Ö
K
E
Eyjafjalla-
jökull
Vík
Ha
Hj
R
Mý
rda
lss
an
du
r
19º10’W 18º20’W 17º30’W
63
º3
0’
N
63
º4
5’
N
64
º0
0’
N
0 24 km
El
dg
já
fis
su
re
Eldgjá lava flow
Skaftáreldar lava flow
Older lavas
Buried lava edge
Kriki hyaloclastite flow
S
La
ka
gíg
ar
Figure 1. The Eldgjá and Laki lava flows. Outline of the Álftaver lava field, including the approximate
location of the lava edge beneath Mýrdalssandur (discontinuous red line) from Larsen (2000). The out-
lines of the Meðalland, Landbrot and Skaftáreldar lava fields are based on Jóhannesson and Sæmundsson
(1990). E: Entujökull, S: Sólheimajökull, Ö: Öldufellsjökull, K: Kötlujkökull, Ha: Hafursey, Hj: Hjörleifshöfði,
R: Rjúpnafell. – Skaftáreldahraunið 1783 og Eldgjárhraunið frá 934 og skipting þess í hraunbreiðurnar sem
kenndar eru við Landbrot, Meðalland og Álftaver. Fyrra mat á staðsetningu hraunjaðars Eldgjárhrauns undir
Mýrdalssandi er sýnt með rauðri brotalínu (Larsen, 2000).
The Kriki hyaloclastite flow deposit is thought to have
formed during the Eldgjá eruption. It’s situated at the
northern margin of the Kötlujökull glacier (Figure 1).
The Kriki flow is a combination of subaerial lava, pil-
low lava, hyaloclastite breccia and hyaloclastite tuff.
The edges of the Kriki flow deposit are buried beneath
alluvium from rivers and jökulhlaups (Larsen, 2000).
Environmental changes at the Mýrdalssandur out-
wash plain
The southern coast of Iceland has evolved drastically
during the Holocene by a combination of glacial, flu-
vial, volcanic and marine processes (Nummedal et
al., 1987). The Mýrdalssandur outwash plain has
mostly been formed in volcanogenic jökulhlaups from
Katla and the surrounding environment has been dras-
tically changed over the past millennium (Thorarins-
son, 1975; Jónsson, 1982; Nummedal et al., 1987;
Larsen, 2000; 2010). The progradation at Mýrdals-
sandur has been very fast (Figure 2). The sediment
deposition from Katla jökulhlaups has extended the
coastline of southern Mýrdalssandur significantly and
it is considered now to lie 2.2–2.5 km south of its lo-
cation in 1660 (Figure 2) (Nummedal et al., 1987).
Katla eruptions melt their way through several
hundred meters of ice producing vast amounts of
meltwater, generating the largest floods observed
in Iceland (Thorarinsson, 1975; Tómasson, 1996;
62 JÖKULL No. 65, 2015