Bjørn WangensteenDepartment of GeosciencesUniversity of Oslo

September, 2004

Águst Guðmundsson, Trond Eiken, Andi Kääb, Herman Farbrot, Ole Humlum and Bernd Etzelmüller

Surface Displacement and Age Estimates for some Debris Covered Glaciers in Northern Iceland

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Permafrost in northern Europe – Permafrost Permafrost in northern Europe – Permafrost distribution and dynamics in Iceland and distribution and dynamics in Iceland and

NorwayNorway

Jarðfræðistofán Geological Services, Reykjavik, Iceland, Jarðfræðistofán Geological Services, Reykjavik, Iceland,

Á. GuðmundssonÁ. Guðmundsson Science Institute, University of Iceland, Prof. H. BjörnssonScience Institute, University of Iceland, Prof. H. Björnsson Department of Geosciences, University of Oslo Department of Geosciences, University of Oslo

Prof. O. Humlum and asoc.prof B. EtzelmüllerProf. O. Humlum and asoc.prof B. Etzelmüller

Main objectives of the projectMain objectives of the project Assess permafrost distribution in Iceland with comparable Assess permafrost distribution in Iceland with comparable

studies in northern Norwaystudies in northern Norway Estimate permafrost thermal regimes and thickness in Estimate permafrost thermal regimes and thickness in

areas of high geothermal activity (Iceland) areas of high geothermal activity (Iceland) Assess rock glacier dynamics in IcelandAssess rock glacier dynamics in Iceland

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This presentation focuses on mapping velocity and This presentation focuses on mapping velocity and estimating age of slopes by digital photogrammetry estimating age of slopes by digital photogrammetry

Technique used for velocity mapping: Technique used for velocity mapping: Cross-correlation matching of orthophotos Cross-correlation matching of orthophotos

Displacement measurements Displacement measurements and age estimates for Site 1and age estimates for Site 1

Displacement measurements Displacement measurements and age estimates for Site 2and age estimates for Site 2

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The technique used for velocity mapping is The technique used for velocity mapping is cross-correlation of orthophotoscross-correlation of orthophotos

DTM

Stereomodel (DFW) +

Match- T

Orthophotos time 1 and 2

Cross-correlation matching of orthos (CIAS)

Multitemporal sets of air photos (stereo pairs)

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Site 1; a debris covered glacier near HólarSite 1; a debris covered glacier near Hólar

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Velocity measurements at site 1; Velocity measurements at site 1; the debris covered glacier at Hólarthe debris covered glacier at Hólar

Glacier front at 930 m.a.s.l

Lower limit of permafrost 850 - 950 m.a.s.l.

Debris cover preserves the glacier

Permafrost creep rather than glacier flow dominates in fast moving areas

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Age estimates for site 1;Age estimates for site 1;the debris covered glacier at Hólarthe debris covered glacier at Hólar

Trajectories based on the displacement field suggest an age of at least 4,500 to 5,000 years

This is based on an assumption of constant velocity

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Site 2; an ice cored moraine complex at HólarSite 2; an ice cored moraine complex at Hólar

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Velocity measurements at site 2; Velocity measurements at site 2; the ice cored moraine complexthe ice cored moraine complex

Active front at 920-30 m.a.s.l.

Lower limit of permafrost 850 – 950 m.a.s.l.

Collapsed front below.

Greatest displacement in the uppermost parts/features

Different velocities for different generations

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Age estimates for site 2; Age estimates for site 2; the ice cored moraine complexthe ice cored moraine complex

Age of at least 1,000 – 1,500 years for the youngest generation

Oldest generation, suggested to at the age of the debris covered glacier of site 1 (4,500 – 5,000 y)

Too few measured points on the other features for a valid age estimate

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In summary, digital photogrammetry reveals In summary, digital photogrammetry reveals new and promising geomorphic results new and promising geomorphic results

Questions?

Velocity fields suggest permafrost conditions

Age estimates implies origin 4,500 y BP; long before the little ice age.

Stable features down to 930 m.a.s.l.