Glacial Landscapes

Erosional Land- scapes  Areal scour vs.  Selective linear erosion

Cirques

Arêtes and Horns  Jointing and mass wasting (two cirques)  Coalescence of three or more cirques

Troughs  “U” shaped –Like a stream, but slower! –X-section area = f(Q) –Elevation = f(Q) at common surface

Trough Erosion  bed  Mass sides (transport)

Paternoster Lakes  Local overdeepenings –Rel. erodibility? –Extension/ compression?  Some evidence of cyclicity

Grinnell Creek

Landforms of Areal Scour  Typically streamlined –Erosional or depositional? –Glacial or glaciofluvial?  Discrete or continuous distribution? [after Rose, 1987]

Outwash Streams and Sediment

Subglacial Channels  Eroded into bedrock (e.g., Antarctica) –Pressure –Tools

 Note: –Escarpment –Notches –Channels

Eskers  Subglacial streams –Deposits –Pressure- driven (may trend uphill!) Copyright © Daryl Dagesse 2002

Moraines Lateral (Stripped) Terminal (single, massive, sharp-crested) (multiple, subtle, hummocky)

Pleistocene Moraines

Moraines (map)  Below ELA  Lastglacial (older?)  Effects on streams: –Moraine- dammed –Glacier- dammed –Outwash

Till Plains/Outwash “Glacier foreland”

Clark Fork of the Yellowstone

Paradise Valley

Kame Terrace  Interaction between valley wall and glacier wall.  Example: Blackfoot River valley – till/kame Terminal moraine Kame terrace

Ice sheet “ground moraine” Kame and kettle topography

Outburst Floods (Jökulhlaup)  Sudden drainage of a glacial lake -Breaching of moraines or floating of ice dams. -Calving of icebergs -Typically cyclic -Massive geomorphic work but potentially devastating [Clague, 1997]

Missoula/Spokane floods

Pluvial Lakes  Closed basins –Bonneville –Lahontan –Owens+

Glaciation and Earth Systems  Oscillating glacial/non-glacial climates  Changing ice/wind/water/coasts… (yr x 10 3 )