Jökull - 01.01.2019, Page 44

Historical accounts of pre-eruption seismicity in Iceland
Figure 4. Map of Hekla Volcano and surrounding regions. Data sources, see Figure 1. – Kort af Heklu og
nánasta umhverfi. Gögn eru þau sömu og á 1. mynd.
Heklugos mikið og var eldurinn uppi nærri 12
mánuði, . . . , en séttu nótt jóla veturinn eftir varð land-
skjálfti svo mikill fyrir sunnan land að ofan féll bærinn
á Skarði eystra og margir bæir aðrir (Thoroddsen,
1899).
1510: This rather large eruption began on July 25 with
a violent phase and an earthquake that appears to have
taken place at the same time (Thorarinsson, 1967).
In Bishops’Annals is the following description
from Skálholt (Figure 4) at a distance of 40 km from
Hekla: „. . . að svo mikill jarðskjálfti og dynkur hefði
komið, að þeir hugðu að allur staðurinn mundi hrapa
í einu; þeir voru að borðum og hljóp hver maður út,
. . . . . . en sem þeir komu út á hlaðið, þá var allt loftið
glóanda að sjá sem það væri í einum loga . . . “
1554: An eruption in the Hekla volcanic system, 10
km SW of the Hekla main edifice (Kjartansson, 1945;
Thorarinsson, 1967; Pedersen et al., 2018), began in
May or early June and lasted about six weeks. It was
accompanied by a sequence of strong earthquakes that
lasted two weeks, but their relation to the timing of
the eruption is uncertain.
1597: An eruption began with an earthquake, immedi-
ately followed by heavy ashfall, on January 3 (based
on a contemporary description by bishop Oddur Ein-
arsson in Skálholt (Thorarinsson, 1967)). It lasted at
least 6 months.
The bishop writes: „. . . um kvöldrökkurstíma,
kom fyrst jarðskjálfti, svo mennn urðu fyrst varir við
nokkra kippi bæði hér og annars staðar, og þar fylgdi
með ógurlegt myrkur, . . . Í sama vetfangi gaus upp úr
Heklu suðaustanverðri eldur og eisa með sandi og
ösku. . . “
1693: The eruption began on February 13 between
19 and 20h with an exceptionally violent phase and
collapse of the NW flank. There were earthquakes as-
sociated with the beginning phase, but no indications
of them occurring before the first eruption was seen.
Some of the descriptions even indicate that the felt
shaking may have been induced by by low-frequency
sound waves in the air [„Af þessu urðu svo miklar
dunur, er allt umhverfið þrumaði og skalf. . . .“ (Thor-
arinsson, 1968)]. The eruption lasted seven months,
possibly as much as 101/2 months.
1725: An eruption began on April 2, in the morning,
and was preceded by strong earthquakes. The earth-
quakes were felt all through the night between April
1 and 2, and one farm, Haukadalur (Figure 4), was
seriously damaged. The eruption was a fairly small
eruption from a fissure near Hekla but not in the main
edifice (Thorarinsson, 1967; Pedersen et al., 2018).
JÖKULL No. 69, 2019 43