Erosional Forms and Landscapes

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Erosional Forms and Landscapes
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Erosional Landscapes

• Areal Scour vs.
• Selective Linear Erosion

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Cirques
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Cirque Form

• Exponential
• Process
• Overdeepened
• Max work _at_ ELA
• Tarn

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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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Arêtes and Horns

• Jointing and mass wasting (two cirques)

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Arêtes and Horns

• Jointing and mass wasting (two cirques)
• Coalescence of three or more cirques

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Troughs

• U shaped
• Like a stream, but slower!
• X-section area f(Q)

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Troughs

• U shaped
• Like a stream, but slower!
• X-section area f(Q)
• Elevation f(Q) at common surface

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Trough Erosion

• Scour _at_ bed
• Mass wasting _at_ sides (transport)

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Trough Erosion

• Scour _at_ bed
• Mass wasting _at_ sides (transport)

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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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