Jökull - 01.12.1999, Blaðsíða 77

Figure 3. Level (VI) and its collapsed and pitted proximal part (Vla). View towards the Höfðabrekkujökull
snout (left) and the Hafursey massif (right). — Horft til austurs að Hafursey, yfir nýlegan árfarveg sem grafið
hefur úr jökulkerjunum á 2. mynd.
gin of the ice whose disappearance led to the formati-
on of the kettlefield and to compare individual kettles
with similar kettles from other plains, such as Skeið-
arársandur (Klimek, 1972; Molewski, 1996).
MORPHOLOGY OF THE KETTLE FIELD
During geomorphological mapping of the terrain, the
number and distribution of kettles was established
along with lithofacies analyses of their deposits.
Their morphometrical data were obtained using sim-
ple geodetic measurements and aerial photographs
from 1992 were used in the morphogenetic evalua-
tion. The basic measurements of the length (L), width
(W) and maximum depth (D) served to establish some
morphometrical indexes. The morphometrical ana-
lysis can help determine the shape of the glacier ice,
and thus an important element of the kettle origin.
Morphometric measurements
Among the 16 analysed kettles three are large (L: 28-
23 m, av. L: 24.9 m); four medium sized (L: 14.6-12
m, av. L: 13 m), and nine are small (L: 9.2-3.4 m,
av. L: 6.7 m) (Figure 4). Four of the kettles are deep
(D: 4.7-3.2 m, av. D: 3.8 m), eight of medium depth
(D: 2.5-1.0 m, av. D: 1.9 m), and four are shallow
(D: 1.0-0.4 m, av. D: 0.8 m). The kettle dimensions
(L, W, D), the azimuths of their L and W axes, along
with four morphometric indexes, i.e. relative depth in-
dex (D/L), equidimensionality (or isometricality) in-
dex (2D/L+W), flatness index (L+W/2D), and elon-
gation index (L/W-l) - are given in Table 1.
The kettles have a somewhat circular shape
with the square of the Pearson correlation index:
R2=0.855. Their form indicates that they were partly
shaped during transport. Short kettles, located close
to each other (Figures 2 and 5: kettles 14 and 17) at-
tain the highest relative depth index (0.41-0.35, Figure
4) whereas larger forms (D/L of 0.16-0.14, kettles 1,
2, and 16) are situated on the peripheries of the lower
part of the kettle field. Ten small and medium length
kettles (L=5.6-13m, D/L=0.28-0.07) occupy the mid-
dle of the field (Figures 2, 4B and 5). Kettle sub-
groups with disproportionately small depths (D: 0.4-
1.2 m) in relation to their length (L: 5.6-8.0 m) and a
low index value D/L (0.07-0.15) are distributed per-
iferally on the kettle field (Figures 4 and 5).
The ratio of the isometricality index and the rela-
tive depth index (Figure 4C). indicates that spherical
blocks of ice did not exist in the kettle field. Only
one kettle (14) has similar dimensions D(2.5 m) >
W(2.4 m). It also has the maximum relative depth in-
dex (0.41). The ratio of the depth and flatness indexes
forms a gentle arch (Figure 4D) indicating the sepa-
rate nature of shaping the flatness of some forms in re-
lation to their isometricality. Three groups of flatness
were distinguished in the kettles: a) very flattened (in-
dex: 12.25-10.25); b) averagely flattened (6.41-5.50),
and c) slightly flattened (4.33-1.68).
Kettles with the greatest relative depth index (av.
D/L: 0.308) are located in the central-eastern part of
the kettle field (Figure 5A: 3-4). These kettles formed
by melting of smaller, rounded blocks of dead ice
JÖKULL, No. 47 75