ABRADED ROCK LANDFORMS

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ABRADED ROCK LANDFORMS
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Cirque Orientation

• Any orientation is possible
• Commonly to NE in Northern Hemisphere

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Cirque Orientation

• Any orientation is possible
• Commonly to NE in Northern Hemisphere

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Why to NE?

• Insolation sensible heat transfer?
• Effect of wind drifting?

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Trough Evolution

• Real form

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Trough Evolution

• Real form
• Modeled form (Harbor, 1992, GSAB)

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Exponential Form

• b exponent
• Form Ratio valley width/ valley depth

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Trough Erosion

• Erosion f(effective pressure)
• Effective f(water pressure)

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Trough Erosion

• Erosion f(effective pressure)
• Effective f(water pressure)
• Erosion f(velocity)

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Trough Erosion

• Erosion f(effective pressure)
• Effective f(water pressure)
• Erosion f(velocity)
• Morphology complex function!

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Trough Evolution

• Modeled by Harbor (1992)
• Results in realistic erosion
• Sequence less realistic!

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Trough Evolution

• Modeled by Harbor (1992)
• Results in realistic erosion
• Sequence less realistic!

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Model Evolution

• Equilibrium glacial trough
• b value between 2 and 2.5
• Form ratio unstable (mass wasting?)

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Paternoster Lakes

• Local overdeepenings
• Rel. erodibility?
• Extension/ compression?
• Some evidence of cyclicity

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Fiords

• Definition
• Drowned glacial troughs
• Appearance
• Steep walls rising from the sea

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Fiords
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Fiords
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Trough Lake Fiord?

• Two Medicine Lk
• Fiordland (NZ)

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Thresholds and Strandflats
Strandflat
Threshold
Moraine?
Moraine?

• Overdeepen at confluences
• Rise to threshold

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Areal Scour (ice sheet)

• Depends heavily upon basal processes f(T)
• Results in a suite of landforms
• May show superimposed patterns

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Areal Scour (ice sheet)
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SLE(ice sheet)

• Examples Finger Lakes
• Selective linear erosion
• Edge of Allegheny Plateau
• Possibly locally wet-based feedback?
• Fluvial?

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SLE(ice sheet)

• Examples Finger Lakes
• Selective linear erosion
• Edge of Allegheny Plateau
• Possibly locally wet-based feedback
• Not the only such example!

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Breached Divides

• New England notches
• Ice advances through notch
• Subglacial drainage?