Surface displacements and surface age estimates for creeping slope landforms in Northern Iceland usi

1
Surface displacements and surface age estimates
for creeping slope landforms in Northern Iceland
using digital photogrammetry B. Wangensteen¹, Á.
Guðmundsson2 , T. Eiken¹, A. Kääb3, H. Farbrot1
and B. Etzelmüller11.Department of Geo
Sciences, University of Oslo, P.O.Box 1047
Blindern, 0316 Oslo, Norway2. Jarðfræðistofán
Geological Services, Raudðagerði 31, 108
Reykjavik, Iceland 3. Department of Geography,
University of Zürich-Irchel, Winterthurerstrasse
190, CH-8057 Zürich, SwitzerlandE-mailbjorn.wang
ensteen_at_geo.uio.no
Introduction In this study, two areas of
different active coarse debris slope processes
are investigated in Northern Iceland. The
objective of the study was to assess slope
dynamics in high-mountain terrain on Iceland, and
its possible implication to mountain permafrost
distribution and Holocene landscape development.
Surface displacements of glacier derived rock
glaciers and a debris-covered glacier in the
Hólar area and a moving debris accumulation at
Almenningsnöf close to Siglufjörður are measured.
The displacement fields are obtained by
cross-correlation matching of multi-temporal
orthophotos (cf. Kääb Vollmer, 2000).
Orthophotos are generated from various series of
air photos from 1964 to 1994.
Figure 4 a) Annual displacement from 1985 to
1994 for the rock glacier complex at Hólar b)
age estimates based on the same velocity field


Moving debris accumulation at Almenningsnöf The
moving debris accumulation is located at the road
along the coast to Siglufjörður at the northern
tip of the Tröllaskagi peninsula (6610'N, 19W).
Geodetic displacement measurements along the road
that crosses the moving debris body undertaken
since 1977 by the Icelandic Road Authorities,
have revealed displacements of up to 1 ma-1.
Figure 1 a) Location of the sites in Iceland b)
Location of the debris covered glacier (1) and
rock glaciers (2-11) at Hólar.
Debris covered glacier and rock glaciers at
Hólar The debris covered glacier and rock
glaciers are located at the central part of the
Tröllaskagi peninsula (6540'N, 19W) close to
Hólar at an altitude of 900-1200 m.a.s.l. The
debris covered area of the glacier is in the
range of 70-80 and up to several metres thick.
The debris layer is therefore protecting the
glacier surface from melting.
Figure 5 a) Location of the moving debris
accumulation at Almenningsnöf b) Orthophoto of
the debris accumulation
The measurements were initiated due to observed
damage on the road. The greatest velocities are
found in the SW part with an average around 0.6
ma-1. In the mid section the velocities are
around 0.2 ma-1, while they are around 0.1 ma-1
at in the upper part of the body. At some places
the movements show rather a discrete than
continuous pattern with zones where the velocity
changes dramatically over small areas. In figure
6b the velocity at both sides of a crevasse is
shown, with displacements of 0.5-0.6 ma-1 on one
side and 0.2 ma-1 on the other.
Figure 2 a) Oblique view of the debris covered
glacier at Hólar b) Photo from the surface of
the same glacier (location marked in a).
The velocity of the debris covered glacier and
the rock glaciers in the Hólar area average from
0.14 ma-1 to 0.67 ma-1. Based on the surface age
results all landforms are suggested to have
developed during the late-Holocene cooling
period, with ages from around 1500 yr, 3000 yr to
5000 yr. These surface age estimates coincide
with data from moraine dating nearby (Stötter
1999) and Holocene climatic development in the
North Atlantic region (Karlén 1988).
Figure 6 a) Yearly displacement from 1985 to
1994 for the debris covered glacier at
Almenningsnöf b) zone of great velocity
differences around a crevasse-looking feature
References Karlén, W., 1988. Scandinavian glacial
and climatic fluctuations during the Holocene.
Quaternary Science Reviews, 7 199-209. Kääb, A.
and Vollmer, M., 2000. Surface Geometry,
Thickness Changes and Flow Fields on Creeping
Mountain Permafrost Automatic Extraction by
Digital Image Analysis. Permafrost and
Periglacial Processes, 11 315-326. Stötter, J.,
Wastl, M., Caseldine, C. and Häberle, T., 1999.
Holocene paleoclimatic reconstruction in
northern Iceland approaches and results.
Quaternary Science Reviews, 18
457-474. Wangensteen, B., Guðmundsson , Á.,
Eiken, T., Kääb, A., Farbrot, H. and Etzelmüller,
B. (in press). Surface displacements and surface
age estimates for creeping slope landforms in
Northern and Eastern Iceland using digital
photogrammetry. Geomorphology.
Figure 3 a) Annual displacement from 1985 to
1994 for the debris covered glacier at Hólar b)
age estimates based on the same velocity field