Jökull - 01.01.2019, Page 39

Einarsson
Figure 2. Map of the Katla and Eyjafjallajökul volcanoes and surrounding regions. Þ is Þykkvabæjarklaustur,
M is Mýrar, H is Höfðabrekka, K Kirkjubæjarklaustur, Ho Holt. Data sources, see Figure 1. – Kort af Kötlu og
Eyjafjallajökli og nærliggjandi svæðum. Þykkvabæjarklaustur, Mýrar, Höfðabrekka, Kirkjubæjarklaustur og
Holt eru merkt með Þ, M, H, K, Ho. Gögn eru þau sömu og á 1. mynd.
jökulhlaups out of the lowest caldera breach towards
the SE, to the Mýrdalssandur outwash plain (Larsen,
2000). The jökulhlaups and the associated ash fall
have been the principal hazards during eruptions of
Katla. The time sequence of large eruptions has been
remarkably regular since 1625, with two eruptions per
century, but the regularity has been broken during the
present repose time, that is the longest repose time of
Katla on record, more than 100 years.
The history of Katla eruptions is reviewed by
Thorarinsson (1975), and recently the historic ac-
counts of the eruptions 1625–1860 were assembled
and reviewed by Jónsson (2018). Earthquakes are
mentioned in connection with eruptions of Katla in
the following cases:
1311: A large eruption began on January 25, but
strong earthquakes were felt in the neighboring dis-
tricts on January 10 and 11, accompanied by light
ashfall, possibly from another eruption site, see below
(Thoroddsen, 1899, 1925). Apparently there were
51 farms severely damaged in the earthquakes. This
account is controversial and has been dismissed by
later authors. No tephra layer is known from Katla
corresponding to this year and this eruption is usually
not listed with Katla eruptions.
1580: The beginning of the eruption on August 11
was accompanied by felt earthquakes but it is not cer-
tain whether or not the earthquakes occurred before
the eruption.
1625: A very thorough contemporary account of this
eruption was written by Þorsteinn Magnússon who
lived at Þykkvabæjarklaustur in Ver, about 35 km SE
of the volcano (Þ in Figure 2). His description of the
beginning is (Jónsson, 2018, p. 65):
38 JÖKULL No. 69, 2019