General Geomorphology Flashcards
Change in storage =
Input - Output
Process rates are modulated by…
Properties of earth surface materials (resistance) Climate (e.g. rainfall intensity, windspeed, runoff) Inherited topography (tectonics, slope gradients)
Erosion (or deposition) is driven by
spatial differences in sediment transfer across the slope
Erosion rate must be greatest where
spatial differences in sediment flux are greatest
Sediment motion depends on
(i) the forces applied by agents of transportation
(ii) the resisting strength of the materials involved
What forces influence earth surface materials?
Driving/motivating forces
– Shearing forces
– Gravitational force (influences weight)
– Lift force (fluids only)
– Buoyancy (fluids only)
What forces influence earth surface materials?
Resisting/impeding forces
– Gravitational force
– Intrinsic strength
What does intrinsic strength vary according to?
Material properties, especially grain size and moisture content
Material moves downslope via:
– Creep
– Solifluction
– Mass-wasting e.g. Rolling/Sliding/Falling
(Diffusive processes)
What processes and factors control the (gradual) downslope movement of sediment?
– Rainsplash
– Bioperturbation
– Ground ‘heaving’ due to
• wetting/dryingcycles
• freeze/thawcycles
• thermal expansion/contraction
Hillslope transport Rate (length/time) is dependent on…..
heave distance, heave frequency and slope
The hillslope diffusion coefficient (kc) is used to describe
the relationship between heave distance and heave frequency
Remember a slope is
just an increase in elevaton (z) over a given distance (x)
First law of motion:
An object either remains at rest or continues to move at a constant velocity, unless acted upon by an external force.
Second law of motion:
F = ma.
Third law of motion:
When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.
First law of thermodynamics :
Energy cannot be created or destroyed
Second law of thermodynamics :
The entropy of an isolated system never decreases.
Third law of thermodynamics :
Systems which best use energy survive
Fluid flow over an object
High velocity fluid=
Low pressure
Lift force occurs which depends velocity gradient.
Fluid flow over an object
Low velocity fluid=
High pressure
Lift force occurs which depends velocity gradient.
On a slope, weight has components that act down the slope and normal to the slope
– The down slope component is a
Driving force
On a slope, weight has components that act down the slope and normal to the slope
– The ‘slope normal’ component is a
Resisting force
Archimedes Principle
An object immersed in a fluid is lighter by an amount equal to the weight of the fluid it displaces
Shear stress
Force exerted as two substances pass over each other
Fluid lift
Force associated with pressure differences around an
object imposed by flow around an object
Buoyancy
Upwards force exerted by a fluid
Sediment flux is controlled by…
the balance between resisting and driving forces
Uniformitarianism
The same laws (processes) observed today have always operated in the same way in the past
Catastrophism
The Earth is shaped by sudden, violent, episodes interrupted by long periods of quiescence
