Jökull - 01.01.2014, Page 25

Volume estimate of nine prehistoric Katla tephra layers
Figure 1. Map showing the study area and its surroundings. The Katla volcanic system is shown in purple, the Katla caldera
is indicated with an ellipse in the southern part of the volcanic system, beneath the Mýrdalsjökull ice cap. Red points indicate
location of measured soil sections. Blue points show outcrops from other studies (Larsen, 2000; Larsen et al., 2005; Larsen,
unpublished data: Óladóttir et al., 2005; 2011a) Inset: map of the Neovolcanic zones of Iceland with following abbreviations:
EVZ - Eastern Volcanic Zone, WVZ - Western Volcanic Zone, NVZ - Northern Volcanic Zone, SVZ - Snæfellsnes Volcanic
Zone. Volcanic systems that produced tephra marker layers used in this study are: H - Hekla, B - Bárdarbunga-Veidivötn,
E - Eyjafjallajökull, T - Torfajökull and K - Katla. – Kort af rannsóknasvæðinu og umhverfi. Eldstöðvakerfið Katla er sýnt
fjólublátt, Kötluaskjan er táknuð með sporöskju í suðurhluta kerfisins undir Mýrdalsjökli. Rauðir punktar sýna staðset-
ningu mældra jarðvegssniða en bláir punktar sýna jarðvegssnið sem mæld voru í öðrum verkefnum (Larsen, 2000; Larsen
o.fl., 2005; Larsen, óbirt gögn; Óladóttir o.fl., 2005; 2011a). EVZ: Eystra gosbeltið, WVZ: Vestur gosbeltið, NVZ: Norður
gosbeltið, SVZ: Snæfellsnes gosbeltið. Gjóskuleiðarlög notuð í þessari rannsókn eru frá eftirfarandi eldstöðvakerfum: H:
Hekla, B: Bárðarbunga-Veiðivötn, E: Eyjafjallajökull, T: Torfajökull og K: Katla.
Two prehistoric Katla tephra layers with a west-
ward distribution have been mapped giving a rough
volume estimate of >1 km3 (uncompacted; Róberts-
dóttir, 1992). Lacasse et al. (1995) estimate the vol-
ume of the Vedde Ash to be a minimum 3.3 km3
and Larsen et al. (2001) have estimated volumes of
six silicic Katla tephra layers ranging from 0.07 to
0.29 km3, uncompacted, but other volume estimates
for prehistoric Katla tephra layers do not exist. How-
ever, there are indications that other prehistoric erup-
tions were of considerable magnitude, e.g. Katla vol-
cano is responsible for 17% of identified tephra lay-
ers around the Vatnajökull ice cap during the last
∼7600 years (Óladóttir et al., 2011a) with an aver-
age thickness of 1.3 cm (range 0.1–11.5 cm). Tephra
from Katla has also been transported to Scandinavia
and the mainland of Europe (e.g. Thorarinsson, 1981;
Wastegård and Davies, 2009; Lane et al., 2010) but
although tephra from the moderate sized Eyjafjalla-
jökull eruption in 2010 (0.27 km3 UCP; Gudmunds-
son et al., 2012) was transported to Europe the histor-
ical documents only account for the larger eruptions
(Thorarinsson, 1981).
JÖKULL No. 64, 2014 25