Múlajökull active drumlin field, Iceland: Solving the riddle of drumlin genesis - verkefnislok
Fréttatilkynning verkefnisstjóra
A total of 110 drumlins were mapped and measured, and their internal stratigraphy described from exposures.
Abstract: In order to shed light on the long-debated question of drumlin formation, the stratigraphy and morphology of drumlins within the active drumlin field at the Múlajökull surge-type glacier in Iceland were studied. Outstanding research questions asked included how drumlins evolve with respect to morphology and sedimentology during several surge cycles, what is the link between surge dynamics and the drumlins, and what is the relative importance of subglacial erosion and deposition in drumlin formation. In addition, the study addressed the questions if drumlins formed by surging glaciers differ from other drumlins and if data from the Múlajökull drumlin field support the suggestion that drumlins are primarily the product of relatively fast flowing glaciers?
Heiti verkefnis: Myndun jökulalda við Múlajökul / Múlajökull active drumlin field, Iceland: Solving the riddle of drumlin genesis
Verkefnisstjóri: Ólafur Ingólfsson, Jarðvísindastofnun Háskólans
Tegund styrks: Verkefnisstyrkur
Styrkár: 2011-2013
Fjárhæð styrks: 19,5 millj kr. alls
Tilvísunarnúmer Rannís: 110237-02
Results: A total of 110 drumlins were mapped and measured, and their internal stratigraphy described from exposures. All exposures reveal several till units where the youngest till commonly truncates older tills on the flanks and the proximal side of the drumlins. Drumlins proximal to the 1992 surge moraine are relatively long and narrow whilst drumlins distal to the moraine are wider and slightly shorter. A conceptual model is proposed to explain the formation of the drumlins at Múlajökull. Radial crevasses formed in the glacier when it initially spilled onto the flat foreland. These crevasses led to spatial differences in normal pressure at the base of the glacier so that deposition was favoured beneath the crevasses and erosion between them. Consequently, the original crevasse pattern of the glacier controlled the location of proto-drumlins. Once the proto-drumlins were formed, a feedback mechanism was established leading to continued crevassing and increased sedimentation at the location of the proto-drumlins. The drumlins are then maintained and their relief and elongation ratio increases as the glacier erodes the sides and drapes a new till layer over the landform. Our study reveals a development of the drumlins toward a more streamlined shape of the proximal landforms that have experienced more surges.
Impact: Our observations of this only known active drumlin field may have implications for drumlins within well-known Pleistocene drumlin fields, and our model may be tested on modern drumlins and drumlin fields that possibly become exposed upon future ice retreat. The project has generated an Iceland-USA research initiative, mainly funded by the National Foundation of USA, “Collaborative research: Testing hypotheses for drumlin formation at Múlajökull, Iceland”, that will run until 2016.
Project output:
Papers published/in review/submitted:
Johnson, M.D., Schomacker, A.,Benediktsson, I.Ö., Geiger, A.D., Ferguson, A. & Ingólfsson, Ó. 2010. Active drumlin field revealed at the margin of Múlajökull, Iceland: A surge-type glacier. Geology 38, 943–946.
Jónsson, S.A., Schomacker, A., Benediktsson, I.Ö., Ingólfsson, Ó. & Johnson, M.D. 2014. The drumlin field and the geomorphology of the Múlajökull surge-type glacier, central Iceland. Geomorphology 207, 213-220.
Benediktsson, I.Ö., Jónsson, S.A., Schomacker, A., Johnson, M.D., Ingólfsson, Ó., (in review). Stratigraphy and morphology of drumlins within the Múlajökull active drumlin field, Iceland, highlight their progressive formation. Journal of Geophysical Research – Earth Surface.
Benediktsson, I.Ö., Schomacker, A., Ingólfsson, Ó., Johnson, M.D., Geiger, A.J., Guðmundsdóttir, E.R., (submitted). Architecture and formation of a Little Ice Age end moraine at Múlajökull, surge-type glacier, Iceland. Journal of Geophysical Research – Earth Surface.
Manuscripts in prep:
Jónsson, S.A., Bergsdóttir, H.L., Ingólfsson, Ó., Benediktsson, I.Ö., Schomacker, A., Jacobson, B. (in prep.). Glacial landsystem of Fláajökull, Iceland. To be submitted to Geografiska Annaler.
Ingólfsson, Ó., Benediktsson, I.Ö. (in prep.). Invited review: Surging glaciers in Iceland – research status and future challenges. Earth Science Reviews.
Jónsson, S.A. (in prep.). PhD thesis.
