Jökull - 01.01.2020, Page 43
Vestergaard et al.
some 40 km NW of Hekla, where his father was
bishop, and from then on followed the eruption. Thus,
the accounts of the initial phases of the eruption was
based on Einar Jónsson (1712–1788) (Thórarinsson,
1967). Thórarinsson (1967) is used in this study as a
"historical source" as it includes several accounts and
interpretations of previous eyewitness-narratives of
the eruptions, e.g. Einar Jónsson (1712–1788) (men-
tioned above) and Rev. Sveinn Vigfússon (1732–
1766). Since we have had access to the Danish-
Figure 2. A) An illustration of lava thickness measurements comprising examples of elevation profiles B), C),
D) and E) that meets and does not meet the requirements for lava thickness measurements. These are respec-
tively marked by accepted or not-accepted in the bottom left of the profile. The base of the flow marks level 0.
It is assumed that the thickness of the lava is reached at the level where the steep slope of the lava front levels
off. This marks level 1. The difference in elevation between level 1 and level 0 is taken as the thickness of
the flow for that particular profile. Average thicknesses are estimated from the accepted profile graphs and are
used in the bulk volume calculations. F) Map of the 1845–46 lava-flow field delineated into nine zones, and
close-up of thickness profile measurements marked with black lines. Zone 1: vent area, complex morphology
changing into channelised flows (approx. slope of area: ≤55◦). Zone 2: complex morphology changing into
channelised flows (≤40◦). Zone 3: lava-falls with complex narrow channels (≤40◦). Zone 4: channelised flows
(≤15◦). Zone 5 and 6: large inflation structure and breakouts though mostly clear in zone 5 (≤15◦). Zone 7
and 9: breakout (≤10◦). Zone 8: channelised flows and possibly inflation and breakout (≤10◦). Background
and boundary outlines as in Figure 1.
40 JÖKULL No. 70, 2020