|Date sent: Tue, 21 Jul 1998 John Shaw <John.Shaw@ualberta.ca>
Here are my responses to your comments. How did melting occur
under an ice sheet? Melting at a glacier bed is a result of
several energy sources: i) Geothermal heat conducted from the
Earth's interior; ii) Frictional heat generated by sliding at
the ice bed; iii) Advected heat from surface water or
groundwater; and iv) Frictional heat produced by viscous
dissipation in flowing water. What prevents a sheet flow from
being concentrated Nothing. That's exactly what the field
evidence tell us. The sheet flows are transient and, after the
formation of drumlin or Rogen fields or hummocky terrain, sheet
flow is concentrated in tunnel channels. Convergent vs divergent
flow patterns? Patterns of drumlins do converge into tunnel
channels near the former ice margins (e.g., the Finger Lakes,
N.Y.) Elsewhere, patterns diverged as water flowed radially
outwards towards distant ice margins (see Prest et al. 1968,
Glacial Map of Canada). In some locations flow di