SURFACE DISPLACEMENT, VOLUME CHANGE AND AGE ESTIMATES FOR SOME
DEBRIS COVERED GLACIERS AND ROCK GLACIERS IN NORTHERN ICELAND USING
DIGITAL PHOTOGRAMMETRY
Bjørn Wangensteen¹, Águst Guðmundsson2 , Trond Eiken¹, Andreas Kääb3, Herman Farbrot1 and
Bernd Etzelmüller1
¹ Department of Geo Sciences, University of Oslo, P.O.Box 1047 Blindern, 0316 Oslo, Norway 2
Jarðfræðistofán Geological Services, Raudðagerði 31, 108 Reykjavik, Iceland 3 Department of
Geography, University of Zürich-Irchel, Wintherthurerstrasse 190, CH-8057 Zürich, Switzerland
The mountain areas of northern Iceland are regions of high periglacial activity, with probable
mountain permafrost above 850 to 950 m.a.s.l. In this study displacement and volume change of
some rock glaciers and a debris covered glacier in the Hólar area (65°40'N, 19°W) at 9-1200
m.a.s.l. are presented. The displacement fields are obtained by cross-correlation matching of multitemporal orthophotos, while the volume changes are found by differencing sets of digital terrain
models (DTM). Both orthophotos and DTMs are generated using a Z/I-Imaging digital
photogrammetric workstation and air photos from 1985 and 1994. Cross-correlation matching is
done with the CIAS-software (Kääb & Vollmer, 2000). GPS measurements of the velocities have
also been initiated at all three sites. The results are analyzed and used for rough age and sediment
flux estimates. In addition, type and cause of movement are discussed further. In the following we
give a short description of the investigated site.
The debris covered glacier and rock glaciers are located at the central part of the Tröllaskagi
peninsula (65°40'N, 19°W) close to Hólar at an altitude of 900-1200 m.a.s.l. Field studies and
empirical spatial modelling indicate the area being close to the lower limit of discontinuous
mountain permafrost in northern Iceland. 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 The results from the cross-correlation matching of orthophotos from 1985 and 1994
give a displacement field of the debris cover that shows signs of both glacier movement and
secondary creep related to permafrost processes. The displacements are in the range from less than
10 cm/y to a maximum of 84 cm/y at the front. The accuracy of the method is estimated to be about
10 cm/y. Differencing of DTMs show an average surface lowering of 1.6 m from 1985-1994. This
lowering is at the scale of the accuracy of the DTMs and therefore not significant. The
displacement of the rock glaciers are considerably lower, reaching about 10cm/y. Flow trajectories
together with average velocity imply an age of about 4.000 years for the debris covered glacier.
Similar studies have also been undertaken at a fast moving debris body close to Siglufjördur
(65°40'N,19°W) located at 0-300 m.a.s.l. and a slow moving debris body at Seydisfjördur
(65°15'N,14°W) located at 0-400 m.a.s.l. These features are located below the present permafrost
limit. But climate in earlier times does not exclude permafrost conditions playing a part in the
development of the features. The measured displacements are up to 86 cm/year in Siglufjördur and
12 cm/year in Seydisfjördur.