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A. Geomorphology

• the study of landforms

• systematic description of landform characteristics

• analysis of formation and modification processes

B. Landform Controls

Driving forces

• solar radiation

• gravity

• earth's internal heat

Resisting forces

• lithology

• geologic structure

Processes: interaction of driving and resisting forces

C. Paradigms of Landscape Formation and Change

Paradigm: dominant worldview; the way in which most scientists think about and understand the world

Catastrophism

• recurrent cataclysmic events occurring over a limited time (earth is young)

Uniformitarianism

• the present is the key to the past

• laws of physics, chemistry, and biology don't change over time

• change is slow and gradual (earth is old)

Davis' Geographical Cycle

• cycle of linear, unidirectional landscape change

• youth, mature, old age stages followed by rejuvenation

Process geomorphology

• driving and resisting forces

• thresholds and equilibrium

D. Process Geomorphology

Process-response relationships

Equilibrium

• "normal" state - characteristic landforms found in particular environments

• definition of "normal" is partly a function of time

• thresholds: limits to equilibrium

Disturbances followed by recovery

• response

  • lag time: delay between change in fundamental controls and landscape response

  • relaxation time: time to return to equilibrium (recovery period)

• frequency, duration, and magnitude of disturbances

  • if relaxation time shorter than frequency of disturbances, landscape dominated by relatively permanent forms

  • if relaxation time longer than recurrence interval of disturbances, landscape dominated by transient landforms

    • relict landforms: landforms created under previous climatic conditions

  • disequilibrium may be common in some landscapes

• feedback

  • negative - helps prevent change; helps system return to equilibrium

  • positive - helps promote change; helps create geomorphically significant disequilibrium

• can't always predict response to a disturbance

  • knowledge of force and resistance insufficient

  • sequence of events, timing of events, and initial conditions

  • complex response

• landscapes may be characterized by:

  • steady state equilibrium with relatively permanent forms

  • multiple potential equilibrium forms (i.e. equilibrium may be characterized by several different forms)

  • no equilibrium; no characteristic forms

E. Summary

• study of characteristics, origin, and processes that shape and modify landforms

• landforms result from interaction of driving forces and resisting forces

• equilibrium and thresholds help define conditions under which temporary or significant change occurs

• landscapes are complex systems with multiple interacting elements, making thresholds (and relaxation time) difficult to define

• major paradigms: catastrophism, uniformitarianism, Davis' geographical cycle, process geomorphology