Jökull - 01.06.2000, Page 31

Helgi Björnsson et al.
H olt
V ík
H atta
Ey ja fja lla jöku ll
T ind fja lla jöku ll
Torfa jöku ll
M a rkarfljó t
Innr i -Em struá
F rem ri -
Em struá
K rossá
B lá fja lla kv ís l
B r
en
n iv
ín
sk
vís
l
H
ól
m
sá
Jök
u lkv
ís l
Le irá
S ká lm
K úð a-
fljó t
M
úlakv ís l
K
lif
a n
d i
Jö
k u
ls
á
40
0
800
1200
8 0
0
1200
Mýrdalsjökull
N
0 5 10 km
20° W
64° N
66° N
15° W
Ice land
M ýrda lssandur
S ó lhe im a-
sandur
F im m vörðu-
há ls
Figure 1. Location map of Mýrdalsjökull and surroundings; outwash plains and glacial rivers. Insert map of
Iceland showing the location of the neo-volcanic zone. – Mýrdalsjökull og nágrenni, jökulsandar, jökulár og
lega gosbeltisins á Íslandi.
1993, 2000), producing 30-35 km


of tephra, erupted
subglacially, mainly from the caldera (Þórarinsson,
1975), and 15 km


of lava, largely originating from
the fissure swarm (Jakobsson, 1979).
The central volcano is one of the most seismically
active in Iceland. The epicenters are bimodal; one
seismic zone lies within the caldera but the other bene-
ath its western rim at Goðabunga (Einarsson, 1977,
1983, 1991; Einarsson and Björnsson, 1987; Einars-
son and Brandsdóttir, 2000).
Since the settlement of Iceland (870 A.D.), twenty
volcanic eruptions, on average two per century, have
been traced to the Mýrdalsjökull volcanic system.
Eruptions under the ice cap rapidly melt large volu-
mes of ice, triggering enormous jökulhlaups from the
glacier margins, frequently breaking off large blocks
of ice (Pálsson 1883, 1945; Eyþórsson, 1945; Þór-
arinsson 1957, 1967, 1975; Rist, 1967a; Einarsson
et al., 1980; Larsen, 1993, 2000; Tómasson, 1996).
The jökulhlaups have threatened human population,
damaged vegetation, disrupted roads on the allu-
vial plains surrounding the ice cap and even genera-
30 JÖKULL No. 49