Advertisement

Structure and Physical State of Glaciers

  • V. V. Bogorodsky
  • C. R. Bentley
  • P. E. Gudmandsen
Part of the Glaciology and Quaternary Geology book series (GQGE, volume 1)

Abstract

Within the first year, the snow flakes falling on a glacier surface are altered to sub-rounded grains, forming firn. Thereafter, in a dry snow zone, where the surface temperature remains below the melting point throughout the year, there are three steps in the metamorphic process of densification. In the first and most rapid step, the grains rearrange themselves with little change in size or shape until they are as tightly packed as they can get. At this point the maximum packing density of about 0.55 mg m−3 has been attained. For further densification, the process slows to modification of the grains by means of sintering—mass transfer between the grains, principally in the vapor phase, recrystallization by molecular diffusion, and plastic deformation of the grains. Grain modification continues until the permeability of the firn has been reduced to zero, which occurs at a density of about 0.83 mg m−3. At this point the firn has been transformed, by definition, into glacier ice. Further densification then proceeds by a still slower process—bulk compression; here squeezing leads to a reduction in the pore size. The final result is ice that contains air bubbles, but that nevertheless is able to attain a density very close to that of single-crystal ice. At pressures of the order of 10 MN m−2, the gas is driven into the lattice of the ice and the bubbles disappear.

Keywords

Ablation Zone Accumulation Zone Glacier Surface Seismic Wave Velocity Deep Drill Hole 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. [1]
    Zotikov, I.A. Thermal regime of the Antarctic ice cover. Leningrad, Hydrometeoizdat, 1977, 168 pp.Google Scholar
  2. [2]
    Kotlyakov, V.M. ‘Snow cover of Antarctica and its role in the present glaciation of the continent. J. Glaciology, 1961, No. 7, 240 pp.Google Scholar
  3. [3]
    Kotlyakov, V.M. Snow cover of the Earth and glaciers. Leningrad, Hydrometeoizdat, 1968, 479 pp.Google Scholar
  4. [4]
    Paterson, W.S.B. The Physics of Glaciers. 2nd Edn. Pergamon 1981, 380 pp.Google Scholar
  5. [5]
    Bentley, C.R. ‘Seismic anisotropy in the West Antarctic ice sheet’. In: Antarctic Snow and Ice Studies II. American Geophys. Union, Antarctic Research Ser., Vol. 16. Washington, 1971, pp. 131–177.Google Scholar
  6. [6]
    Gow, A.J. ‘Results of measurements in the 309-meter bore hole at Byrd Station, Antarctica’. J. Glaciol., 1963, 4, 771–784.Google Scholar
  7. [7]
    Gow, A.J. ‘The inner structure of the Ross Ice Shelf at Little America V, Antarctica, as revealed by deep core drilling’. General Assembly of Berkeley, IASH Pub. No. 61, 1963, pp. 272–284.Google Scholar
  8. [8]
    Gow, A.J. ‘Preliminary results of studies of ice cores from the 2164 m deep drill hole, Byrd Station, Antarctica’. International Symp. on Antarctic Glaciol. Exploration (ISAGE). IASH Pub. No. 86, 1970, pp. 78 - 90.Google Scholar
  9. [9]
    Langway, C.C. ‘Stratigraphic analysis of a deep ice core from Greenland’. Geol. Soc. Amer. Special Paper 125, 1970, 186 pp.Google Scholar
  10. [10]
    Langway, C.C. ‘Antarctic ice core studies’. Antarctic J. U.S., 1975, 10, 152–153.Google Scholar
  11. [11]
    Post, A., LaChapelle E.R. Glacier ice. Seattle, Univ. of Washington Press, 1971. attice of the ice and the bubbles disappear.Google Scholar

Copyright information

© D. Reidel Publishing Company, Dordrecht, Holland 1985

Authors and Affiliations

  • V. V. Bogorodsky
    • 1
  • C. R. Bentley
    • 2
  • P. E. Gudmandsen
    • 3
  1. 1.Arctic and Antarctic Scientific Research InstituteLeningradUSSR
  2. 2.Geophysical and Polar Research CenterUniversity of Wisconsin-MadisonUSA
  3. 3.Technical University of DenmarkCopenhagenDenmark

Personalised recommendations