Field and Laboratory Study of the Flàajökull Glacier, Iceland
The increased surface melting of the outlet glaciers of the Vatnajökull Ice Cap has a profound affect on the dynamics of the ice-bed couple and landform genesis. Soft-bedded glaciers are largely inaccessible, which creates a problem. One challenge is to understand the complex interactions of the gla...
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UWM Digital Commons
2015
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| Online Access: | https://dc.uwm.edu/etd/1057 https://dc.uwm.edu/context/etd/article/2062/viewcontent/JacobsonJr_uwm_0263D_11209.pdf |
| Summary: | The increased surface melting of the outlet glaciers of the Vatnajökull Ice Cap has a profound affect on the dynamics of the ice-bed couple and landform genesis. Soft-bedded glaciers are largely inaccessible, which creates a problem. One challenge is to understand the complex interactions of the glacier bed and its resultant depositional and deformational landform systems. This study investigates an outlet glacier from the Vatnajökull Ice Cap, described herein as the Fláajökull glacier system. To circumvent some of these problems, three separate projects were conducted in this dissertation: (1) magnetic fabric study of effective pressure (difference between the ice-overburden pressure and pore-water pressure) and shear rate (glacier velocity) using a laboratory ring-shear device; (2) glaciological analysis of magnetic fabrics and c-axis orientations of dirty ice veins; and (3) investigation of drumlin formation using magnetic till fabrics and field relationships. Several hypotheses were addressed for each of these studies, which include: (1) to determine if fabric strength is independent of shear rate and effective pressure. This hypothesis was tested and the results confirmed that the fabric strength (S1 eigenvalue) was independent of shear rate and effective pressure. Based on these results, effective pressure and shear rate cannot be interpreted from fabric strength evidence from glacial deposits; (2) in the glaciological study, I hypothesized that the dirty ice veins were sub-vertically sheared from the bed near the ice front, but then moderately deformed. Results from the magnetic fabrics indicate that the maximum K1 susceptibility axis (77º plunge) is approximately parallel to the vein margins verify that the injection was sub-vertical. The long axes of the recrystallized ice grains (parallel to foliation plane defined by K1 - K2) appeared to show a good correlation with the plunge of the maximum K1 susceptibility. Also, the eigenvector plunge of the c-axes was approximately normal to the shear plane, ... |
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