A crystallographic investigation of glacier structure and the mechanism of glacier flow

Perutz, M. F.; Seligman, G.

doi:10.1098/rspa.1939.0108

Cited by 46 publications

(5 citation statements)

References 4 publications

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“…Seligman and his colleagues pioneered the use of thin sections of glacier ice, studied under polarized light, to investigate the transformation from snow, through firn, into glacier ice, followed by the effects of glacier flow. This was achieved by measuring ice crystal orientations and generating fabric diagrams that record their orientations in 3-D (Perutz & Seligman, 1939). These methods continue in use to this day, albeit the original universal stage method of measuring orientations (Rigsby, 1960) has been replaced by more sophisticated technology, such as using an automated fabric analyzer (Wilson et al, 2003).…”

Section: Microstructure and Crystal Fabric Of Glacier Icementioning

confidence: 99%

Structures and Deformation in Glaciers and Ice Sheets

Jennings

Hambrey

2021

Reviews of Geophysics

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The purpose of this review is to provide a comprehensive assessment of the state of knowledge concerning the manner in which macroscopic structures evolve within glaciers, and to evaluate their meaning in terms of understanding the flow of glaciers and ice sheets. Using concepts drawn from structural geology (e.g., Fossen, 2010;Hobbs et al., 1976;Ramsay, 1967;Ramsay & Huber, 1983), attention is drawn to the similarities between glacier ice and deformed rocks. The review emphasizes those structures that can be observed at the glacier surface and considers their three-dimensional (3-D) geometry. Structures in glaciers are commonly complex and challenging to interpret, especially where several phases of deformation over-print one another. Hence, to aid the reader in the field, many of the described structures and their cross-cutting relationships are illustrated in photographs, maps, and conceptual diagrams, with examples ranging from the Arctic, through mid-latitude mountain ranges, to the Antarctic.

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Section: Microstructure and Crystal Fabric Of Glacier Icementioning

confidence: 99%

Structures and Deformation in Glaciers and Ice Sheets

Jennings

Hambrey

2021

Reviews of Geophysics

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“…In contrast to the long history of crystallographic fabric measurements in deep firn and ice (Perutz et al, 1939;Gow and Williamson, 1976), the crystallographic fabric of snow has only recently been studied. The evolution of the crystallographic fabric of a natural alpine snow sample subjected to a temperature gradient was analyzed from thin sections (Riche et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

On the Birth of Structural and Crystallographic Fabric Signals in Polar Snow: A Case Study From the EastGRIP Snowpack

Montagnat

Löwe²,

Calonne

et al. 2020

Front. Earth Sci.

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The role of near-surface snow processes for the formation of climate signals through densification into deep polar firn is still barely understood. To this end we have analyzed a shallow snow pit (0-3 meters) from EastGRIP (Greenland) and derived high-resolution profiles of different types of mechanically relevant fabric tensors. The structural fabric, which characterizes the anisotropic geometry of ice matrix and pore space, was obtained by X-ray tomography. The crystallographic fabric, which characterizes the anisotropic distribution of the c-axis (or optical axis) orientations of snow crystals, was obtained from automatic analysis of thin sections. The structural fabric profile unambiguously reveals the seasonal cycles at EastGRIP, as a consequence of temperature gradient metamorphism, and in contrast to featureless signals of parameters like density or specific surface area. The crystallographic fabric profile unambiguously reveals a signal of cluster-type texture already at shallow depth. We make use of order of magnitude estimates for the formation time of both fabric signals and discuss potential coupling effects in the context of snow and firn densification.

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“…Though th e texture of firn a nd of deep ice at the polar ice caps is fairly well known, thanks to the work of, for example, Schytt ( 1958), Langwa y ( 1967, and Gow (1970), the same is not true for the a ccumulation zone of temperate glaciers, except for the pioneeing work of Perutz and Seligman ( 1939). W e have tried to fill this gap by drilling to bedrock in the accumula tion zone of a temperate glacier .…”

Section: Introductionmentioning

confidence: 99%

Study of an Ice Core to the Bedrock in the Accumulation zone of an Alpine Glacier

Vallon¹,

Petit²,

Fabre³

1976

J. Glaciol.

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ABSTRACT. A water table appea ring every summer where the ice begins, at a depth of approximately 30 m, accelerates the transformation of firn into ice during the summer (80% of the ice formed every year appears in less than 2 months ). The ice formed in this way con tains from 0 to 0.6 % water. The average water content increases gradually with the depth because of the h eat of deformation. But, near bedrock, between 180 and 187 m, the permeability of the blue ice is such that the water content drops (0.3 % as Compared to 1.3 % between 160 and 180 m ) .From a depth of 33 m , a foliation of sedime ntary origin gradually develops in the ice. I ts dip increases regularly to a d epth of 145 m. At 145 m it jumps suddenly from 20° to 40°, then at 170 m from 40° to 65°, which can be expl a in ed by old modifications in the bergschrund. This foliation disappears near bedrock ( 180-187 m ), where there are no bubbles in the ice.The average size of an ice crystal increases slowly in the firn, sh ows seasonal fluctu a ti ons between 30 and 50 m, then jumps from a diameter of I or 2 mm to 10 or 20 mm between 50 and 80 m. Between 180 and 187 m, the ice is made of large crystals (3-10 cm diameter; the figure, however, is probably inexact due to a recrystallization of the samples) .The very strong sub-ve rti ca l orientation of the optic axes of the firn crys tals disappears quickly, and from 66 m on, in ice with large crystals, a fabric of multiple maxima appears (genera ll y, 3 or 4 directions, forming a tri a ngle or a rhombus) . On the other h and, in the small crystals that form bands parallel to the plane of foliation, only one direction of preferential orie ntation can be seen, or two close to one another. Crystals of intermed iate size ( 10 to 50 mm ) generally have two directions of preferred orie nta tion at an a ngle of approximately 50° to one another. No matte r h ow big the crystals a re, the angle be twee n th e most common c-ax is orientation and the vertica l does not ch ange from 60 to 170 m d epth.R ESU,"L Etude d'une caroUe de glace jllsqll'au lit dons la zone d'accumlllation d'WI glacier tempire.Un ni veau aq uifere appa ra issa nt chaque ete au contact de la gl ace, vers 30 m d e profondeur, a ccelere la transformation d u neve e n g lace durant l'ete (80% de la glace formee chaq ue a nnee apparait en 2 mois) . La glace a insi fo rm ee renferme d e 0 it 0,6°{, d 'ea u liquid e. La teneur moye nn e e n ea u liquide a ugm e nte progressivem e nt a vec la profondeur, par su ite de la chaleur d e deformation. M a is a u contact du lit, e ntre 180 et 187 m , la permeab ilite d e la glace ble ue est tell e que la te neur en eau devi ent faible (0,3 % contr'e 1,3 % entre 160 et 180 m ) .Dans la gl ace, it partir d e 33 m d e profondeur, se developpe progressivement une foliation d'origine sedimenta ire. Son pendage eroit regu lierement jusqu'it 145 m d e profondeur. A 145 e t '70 m, il passe brusqueme nt de 20° it 40° puis d e 40° it 65°, ce qu 'on explique par d'aneiennes modifi ca tions de la rim aye. Ce tte ...

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A crystallographic investigation of glacier structure and the mechanism of glacier flow

Cited by 46 publications

References 4 publications

Structures and Deformation in Glaciers and Ice Sheets

Structures and Deformation in Glaciers and Ice Sheets

On the Birth of Structural and Crystallographic Fabric Signals in Polar Snow: A Case Study From the EastGRIP Snowpack

Study of an Ice Core to the Bedrock in the Accumulation zone of an Alpine Glacier

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