The Flow of Glaciers and Ice-Sheets as a Problem in Plasticity

摘要: A calculation is made of the distribution stress and velocity in an ideal glacier ice-sheet. The ice assumed to have a constant yield obey, like other polycrystalline plastic aggregates, Levy-Mises equations flow either Mises or Tresca criterion yielding. solution obtained for represents two-dimensional long slab down gently undulating rough slope. addition upper surface by snowfall removal ablation are allowed for, but frictional resistance sides valley neglected. Two states possible, 'active' 'passive', corresponding active passive Rankine soil mechanics. Which these occurs at given place depends upon relative magnitudes curvature bed rate ablation; simple algebraic expression this dependence obtained. In both greatest decreases with depth according elliptical law. It shown that, accordance observation, crevasses limited can open not flow. slip-line field problem has close connexion directions positions shear faults (although laminated structure doubtless also important factor here). be expected similar 'thrust planes' often seen on glaciers. theory suggests that complementary sort fault opposite direction movement may occur-and there some observational evidence this. tendency glaciers accentuate hollows their beds connected suggestion erosion should proceed faster under than second formally large ice-sheet, such as Greenland ice-cap. If horizontal profile calculated formed from parts two parabolas, maximum height being ice. accumulation area active. everywhere while bed. thus gives no support belief weight above squeezes out underlying rate.