Figure 4-3 for Sean Mewhinney's Minds in Ablation


Figure 4-3

Idealized cross-section of an ice sheet. The horizonal lines represent annual layers, which thin progressively as they sink toward the base of the ice sheet. The central vertical line I-I represents an ice divide. The curved lines show the direction of ice flow downward from the site of deposition and outward toward the margin.

"When the equilibrium line (the line where the annual loss of ice by melting exactly balances the annual mass input by snow deposition) is reached, the ice layers begin to move up relative to the surface and then resurface downslope from the equilibrium line. The further inland the ice was originally deposited, the closer to the ice margin the ice will reappear, and the older the surface ice will be."

Quotation from M. Maurette et al., "Placers of Cosmic Dust in the Blue Ice Lakes of Greenland," Science, August 22, 1986, p. 870. The arrows to the left of the vertical line C-C represent the horizontal velocity of the ice at different depths, which falls to zero at the bottom for an ice sheet frozen to its bed. Source of illustration: W. Dansgaard et al., "Climatic Record Revealed by the Camp Century Ice Core," in Karl Turekian, ed., The Late Cenozoic Glacial Ages (Yale Univ. Press, 1971).


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Last modified by pib on October 28, 2003.