Surface displacements and surface age estimates for creeping slope
landforms in Northern Iceland using digital photogrammetry
B. Wangensteen¹, Á.
2
Guðmundsson
, T. Eiken¹, A.
3
Kääb ,
H.
1
Farbrot
and B.
1
Etzelmüller
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, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
E-mail:bjorn.wangensteen@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 debriscovered glacier in the Hólar area and a moving debris
accumulation at Almenningsnöf close to Siglufjörður are
measured. The displacement fields are obtained by crosscorrelation 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
(66°10'N, 19°W). 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 (65°40'N, 19°W) 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
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).
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 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
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
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.