Jökull - 01.12.1999, Blaðsíða 61

Relief of the Höfðabrekkujökull forefield, South Iceland, in
light of geomorphological mapping
Edward Wisniewski1, Leon Andrzejewski2, and Antoni Olszewski2
1 Institute of Geography, Pedagogical University, Partyzantów 27, 76-200 Slupsk, Poland
2 Institute of Geography, Nicholas Copernicus University, Fredry 6/8, 87-100 Torun, Poland
Abstract — A series of genetic forms associated with recent glacier movements, jökulhlaups and meltwater
flow were distinguished during detailed geomorphological mapping of the Höfðabrekkujökull forefield. Out-
wash levels with ground moraines and end moraine hillocks, demarcating different glacier halts, dominate
the glacier forefield. Four generations ofend moraines were identified. Tlie oldest moraines probably form-
ed at the end ofthe last glacial period (during Younger Dryas) or in early Holocene (Preboreal). Other mor-
aines mark the maximum extent ofthe glacier during the “ Little Ice Age ” (1600-1920), prior to 1945 and
most recently in 1992.
INTRODUCTION
The geomorphological map of the Höfðabrekkujökull
forefield presented here is the result of fieldwork car-
ried out during the summers of 1995, 1996, and 1997.
Geomorphological mapping involves recording all
surface forms occurring in a given area and precisely
locating them with the aid of topographical maps and
aerial photographs. Initially each form must be classi-
fied into a given genetic group of forms by establish-
ing their morphometrical and morphographical fea-
tures, their age, and their geological structure. Geo-
morphological research therefore requires assessment
of all elements which make up the study terrain, both
from the point of view of quality, i.e. their appearance,
genesis and age, and from the point of view of quan-
tity, e.g. distribution of the forms, their size, number
and direction. As a result, the geomorphological map
represents a detailed picture of the relief of the study
area within a genetic and chronological framework
and provides the basis for the interpretation of the dif-
ferent stages of geomorphological development.
While making the map on the basis of aerial pho-
tographs, the following genetic categories of forms
were distinguished; forms generated by the accumu-
lative or the transformational activity of the outlet
glacier, forms generated by accumulative or erosive
activity of the meltwaters, forms created during the
degradation of dead ice, nival forms, forms of eolian
origin, volcanic forms, and denudational forms.
CHARACTERIZATION OF THE
MÝRDALSJÖKULL ICE CAP AND THE
HÖFÐAB REKKUJÖKULL OUTLET
GLACIER
Kriiger (1994) divided the fourth largest ice cap in Ice-
land, Mýrdalsjökull (596 km2) into two regions: a) the
ice cap itself (1100-1480 m a.s.l.) which covers the
caldera of the active volcano, Katla and its surround-
ings (Björnsson, 1979) and b) the peripheral zone
and the outlet glaciers, including the largest of them,
Höfðabrekkujökull (also called Kötlujökull). In our
opinion, Mýrdalsjökull displays clear morphostruc-
tural surface triplicity (Figure 1), namely:
A. A glaciomorphological centre within which it
is possible to distinguish a) the oval ice domes of
Goðabunga (1480 m a.s.l.) and Háabunga (about 1400
m a.s.l.), b) elongated ridges of ice divide flats (e.g.
JÖKULL, No. 47 59