Jökull - 01.01.2021, Page 67

Bedrock and tephra layer topography within the Katla caldera
Figure 12. a) The data used for interpolating a new bedrock DEM near the estimated location of the 1918
eruption site (area location within the caldera shown with a blue square on inlet) posted on a surface contour
map (10 m contour interval) of September 2019. Blue dotted clusters and lines show locations of RES-data
obtained in 2012–2019 (both 2D and 3D migrated). In May 2021, RES-profiles, allowing 3D migration (cluster
of magenta dots) as well as 2D migration (yellow dotted lines), were added. b) The resulting bedrock DEM.
The area outside the white dotted line, covered with transparent grey mask indicates where bedrock DEM is
unchanged from Björnsson et al. (2000). The dashed blue line indicates a clear ridge in the bedrock topography
at the boundary of the estimated eruption site (Gudmundsson et al., 2021, shown with red dotted ellipse). – a)
Staðsetning íssjármælinga sem nýtt var við gerð botnhæðarkorts af 1918 eldstöðinni (Magnús T. Guðmundsson
o.fl., 2021, sýnd með rauðri sporbaugslaga punktalínu) og nágrenni (afmarkað með bláu boxi á innskotsmynd),
lagt ofan á yfirborðshæðarkort (10 m hæðarlínubil) frá september 2019. Bláar punktalínur og skellur sýna
mælingar frá 2012–2019. Þann 15. maí 2021 var bætt við íssjármælingum sem unnið var úr með þrívíðri
(purpurarauðar punktaskellur) og tvívíðri (gular punktalínur) staðsetningarleiðréttingu á endurkastsflötum. b)
Nýtt botnhæðarkort (10 hæðarlínubil) af svæðinu. Skyggða svæðið utan hvítu punktalínunnar er óbreytt frá
botnkorti Helga Björnssonar o.fl. (2000). Bláa brotalínan gefur til kynna afgerandi hrygg í botnlandslagi í
jaðri áætlaðrar gosstöðvar.
this issue of Jökull. The new survey reveals much
more complex topography in this area than the lim-
ited RES-data in this area acquired in previous studies
(Figure 2). The complex topography is not surpris-
ing since most eruptions in the past centuries proba-
bly took place within or near this area (Larsen et al.,
2013). It is difficult to tell whether any of the ob-
served landforms within this area were formed dur-
ing the eruption 1918. The most conspicuous form
is a ridge aligned from southwest to northeast, partly
within the northern part of the suggested eruption area
but extending at least 250 m further north. Extended
work, beyond the scope of this paper, including com-
parison with photographs of the eruption site taken by
JÖKULL No. 71, 2021 65