slope:
- inclined surface ---> hillslope
- angle of inclination ---> slope angle
- can be:
● sub-aerial - exposed
● sub-marine - underwater
● aggradational - depositional
● degradational - erosional
hillslope: area between a watershed (drainage basin divide) and the
base - may contain river/stream
Controls on slopes
Climate
humid areas - slopes are frequently rounder ---> chemical weathering,
soil creep and fluvial transport
arid regions - slopes are jagged/straight ---> physical weathering and
sheetwash
the climate factors in each area (rainfall type/intensity, temperature
range, humidity) will have an influence over the size and shape of the
slopes
- climatic geomorphology: climate conditions produce different slope
shapes
Geological structure
includes: faulting, slope dip and vulcanicity
- factors influence the strength of the rock ---> can create lines of
weakness
- rock type + character ---> affect the resistance to weathering and
downslope movement
- influences occurrence of landslips:
● composite cliffs are more vulnerable to landslides -
differential erosion
Soil
, part of regolith = a region of loose unconsolidated rock and dust that sits
atop a layer of bedrock. On Earth, regolith also includes soil.
- structure + texture ---> porosity and permeability
- a soil's capacity to hold water can determine the existence of mass
movements in the area
Aspect
the direction a slope faces
- asymmetric valley - results from the different conditions which
slopes are subjected to. In the Northern Hemisphere:
● slopes facing the South are subjected to many cycles of
freeze-thaw
● slopes facing the North remain in the shade
● solifluction + runoff ---> shape of slopes
Vegetation
interception + storage of moisture ---> decrease in overland runoff
- deforested slopes are exposed to erosion + undercutting +
saturation - California fires in 2018
- vegetation may also increase landslides - densely forested area:
● build-up of soil between trees ---> deepening regolith +
increasing potential for failure.
Mass movements
any large-scale movements of the surface of the Earth that are not
accompanied by a moving agent (river, ocean…)
very slow movements - soil creep
- more continuous ---> occur frequently
fast movement - avalanches
- infrequent
dry movement - rockfalls
fluid movements - mudflows
Classification
- speed of movement
- inclined surface ---> hillslope
- angle of inclination ---> slope angle
- can be:
● sub-aerial - exposed
● sub-marine - underwater
● aggradational - depositional
● degradational - erosional
hillslope: area between a watershed (drainage basin divide) and the
base - may contain river/stream
Controls on slopes
Climate
humid areas - slopes are frequently rounder ---> chemical weathering,
soil creep and fluvial transport
arid regions - slopes are jagged/straight ---> physical weathering and
sheetwash
the climate factors in each area (rainfall type/intensity, temperature
range, humidity) will have an influence over the size and shape of the
slopes
- climatic geomorphology: climate conditions produce different slope
shapes
Geological structure
includes: faulting, slope dip and vulcanicity
- factors influence the strength of the rock ---> can create lines of
weakness
- rock type + character ---> affect the resistance to weathering and
downslope movement
- influences occurrence of landslips:
● composite cliffs are more vulnerable to landslides -
differential erosion
Soil
, part of regolith = a region of loose unconsolidated rock and dust that sits
atop a layer of bedrock. On Earth, regolith also includes soil.
- structure + texture ---> porosity and permeability
- a soil's capacity to hold water can determine the existence of mass
movements in the area
Aspect
the direction a slope faces
- asymmetric valley - results from the different conditions which
slopes are subjected to. In the Northern Hemisphere:
● slopes facing the South are subjected to many cycles of
freeze-thaw
● slopes facing the North remain in the shade
● solifluction + runoff ---> shape of slopes
Vegetation
interception + storage of moisture ---> decrease in overland runoff
- deforested slopes are exposed to erosion + undercutting +
saturation - California fires in 2018
- vegetation may also increase landslides - densely forested area:
● build-up of soil between trees ---> deepening regolith +
increasing potential for failure.
Mass movements
any large-scale movements of the surface of the Earth that are not
accompanied by a moving agent (river, ocean…)
very slow movements - soil creep
- more continuous ---> occur frequently
fast movement - avalanches
- infrequent
dry movement - rockfalls
fluid movements - mudflows
Classification
- speed of movement
