Jökull - 01.12.2003, Blaðsíða 45

The 1783–1785 Laki-Grímsvötn eruptions
Table B: Explosive activity, continued.
Date Index Source Quotation
18 July B53 4, p. 22 ...sandy ash was dispersed all over the Fire districts such that in the Fljótshverfi district all grazing fields were destroyed
as far as to the river Djúpá. [Tephra-fall from Grímsvötn volcano.]
19 July B54 2, p. 65 ...the volcanic plume stayed north of the mountains bordering the Síða and was directed towards west, occasional thunder
was heard. [Continued tephra fall from Grímsvötn?]
20 July B55 4, p. 22 ...same cloudy weather with thunder, lightning, cracking sounds and earthquakes.
21 July B56 4, p. 23 The plumewas directed towards the northwest and after this day no loud rumbling sounds were heard from this Vesturgjá,
despite fires continued to burn and flow from it into September.
22 July–2
August
B57 2, p. 66 ...occasional heavy rainfall, and during this time columns of fire and smoke with intermittent thunder and rumbling were
observed in the pasture.
24 July B58 4, p. 23 ...intensive fire coloured glare was seen in the sky...
24 July B59 7, p. 281 Fine-grained pumice-like material, which resembled finely cut tobacco, has been observed to fall in many localities, for
example on the Kjölur route along the Blanda River. [The section of the Kjölur route mentioned here is located in eastern
part of Húnavatnssýsla in North Iceland, 250 km north-northwest of the Laki fissures. The timing of this tephra fall is
uncertain but it obviously occurred before 24 July].
25 July B60 4, p. 23 Same fire coloured glare.
28 July B61 4, p. 23 ...rain in westerly wind, with sandy ash and a bad smell.
29 July B62 4, p. 25 ...calmweather, for the first time rumble and a boiling sound was heard northeast of Kaldbakur mountain, on a strike with
a high mountain called Blængur. The rumble and cracking was not any less than was heard earlier from Útnorðursgjá,
which had dwindled considerably at this stage. Later that day an awesome plume emerged from the site with ash-fall
that was largely dispersed over the Fljótshverfi district and the eastern part of the Síða district, reducing daylight such
that visibility in our homes was greatly diminished. [The line of sight from Prestbakki to Blængur is the direction to the
first fissure east of Laki mountain, labelled 6 on Figure 2.]
30 July B63 4, p. 26 ...thunder, rumbling and cracking sounds were heard almost continuously from all sides.
in July B64 4, p. 25 Near the farm Skaftárdalur on the eastern side of the Skaftá River gorge lava blobs [spatter bombs], which had fallen out
of the air, could still be seen, some were elongated and twisted together like a cow-dung. Some were still in one piece;
others had broken up on impact. [These spatter bombs were produced by rootless eruption within the lava flow, see also
description on 18 July.]
in July B65 4, p. 25 From there [Skaftárdalur farm] columns of fire were seen at two locations until 14 January 1784.
1–3 Aug. B66 4, p. 26 ...same boiling continued to be heard from this gjá [Landnorðursgjá], along with earthquakes, rumbling, thunder and
lightning...
6 Aug. B67 6, p. 297 Still the entire Fljótshverfi district was completely covered with sandy ash [i.e., from the tephra fall on 29–30 July].
9 Aug. B68 2, p. 66s ...intensive thunder and lightning was noticed around the fissure north of Fljótshverfi.
10–17 Aug. B69 4, p. 27 ...the boiling continued to be heard from Landnorðursgjá...
14 August B70 4, p. 27 ...the plume was directed away [from the rural settlement] by south-westerly wind.
<15 Aug. B71 12, p. 279 Two columns of smoke were seen from the farm Húsafell in Borgarfjarðarsýsla, which rose above the eastern part of
Kaldidalur Valley. [This description is in a letter written by Ólafur Stephensen on 15 August 1783. Here he is describing
the eruption columns of the Laki eruption. From this location the columns must have been viewed over the mountains at
the southern end of Langjökull glacier and to be seen from Húsafell the plume must have been at least 8.5 km high and
most likely considerably higher].
17–23 Aug. B72 4, p. 28 ... the same boiling sound was heard from Landnorðursgjá and showers, containing sandy ash, fell frequently [in the
Síða district].
23–31 Aug. B73 4, p. 28 ... activity continued as previously described, but now again intense tremor and cracking was felt from Austurgjá.
in August B74 4, p. 27 When the smokes coalesced and the fumes in them became too heavy, a stinking and sandy rain fell out of the cloud with
lightning and thunder. This occurred despite that clear and bright weather was around us.
in August B75 4, p. 27 When the activity dwindled, which commonly was at its peak during new and/or full moon, the fields recovered to some
degree.
1–7 Sept. B76 4, p. 28 Rain and acrid rain, fog and mist, thunder and lightning occurred frequently that week [in the Fire districts].
7 Sept. B77 7, p. 281 ...in the morning of 7 September fine-grained ash fell on a boat west of Vestmannaeyjar, so the sail and cloth covers
became dark grey in colour in 2–3 hours.
14 Sept. B78 4, p. 29 ...heavy ash-fall in easterly wind, which only reached as far west as Geirlandsá. [Geirlandsá River originates in Lauf-
fellsmýrar up in the Síða highlands flowing almost directly south to the central part of the Síða district. Thus it is
impossible that this ash-fall came from the Laki fissures because the wind was blowing from the east at the time. The
only possible eruption site which could have produced this ash and caused this type of dispersal is Grímsvötn.]
14–26 Sept. B79 4, p. 29 ...at nights the glare from the eruptive fissure reached up to the middle of the sky, especially in two places as it was seen
from Prestbakki. From Vesturgjá the glare was seen between Lambatungur and Kaldbakur mountain, but from Austurgjá
between Kaldbakur and Vothamrar.
26 Sept. B80 4, p. 29 An additional column of fire and steam, which had been seen few times before, appeared far east- northeast from Síða,
due north of Lómagnúpur, but northwest from Öræfi. This activity was ongoing until 24 October. That day intensive
earthquakes and strong sulfuric stench was noted from east-northeast, which indicated that this event was not all over yet
as became evident later... [These directions leave no doubt that Austur-Landnorðursgjá is Grímsvötn volcano].
25 Oct. B81 4, p. 30 ...a high column of fire ascended into the air from there [Grímsvötn] and was followed by an intensive lava surge [from
Útnorðursgjá] along with rumbling and claps for the next five days.
24 Nov. B82 4, p. 31 The activity was still so intensive in east-northeast, that the column of firewere seen above mountain Kaldbakur. In early
December the activity started to dwindle and the glare, which had been seen almost daily above the three gjá’s or vent
areas, diminished.
JÖKULL No. 53, 2003 43