Environmental Engineering Reference
In-Depth Information
deepens existing valley networks. Advancing cirque glaciers coalesce into valley glaciers,
concentrating erosive power below their confluences. Troughs develop characteristic
parabolic cross-sections typically 0·5-2·0 km deep and with upper rock walls reaching
65°-85° at their steepest above relatively flat floors. Irregular long-profiles reflect
extending and compressive flow regimes, with rock basins excavated below ice
confluences or in structurally weak zones.
Riegels
or cross-valley barriers separate the
basins and rock surfaces are polished and striated by vigorous ice flow. Streamlined
roches moutonnées
are abundant.
Plate 15.10
Supraglacial meltwater stream network (top left),
a single supraglacial stream entering a moulin (bottom) and
a discharge portal on the Taku glacier, Alaska (top right).
Photos: Ken Addison.
