Slopes

topography of South Africa (6 + 2-4 each)

1. Interior Plateau

-1000m altitude

-increases in altitude from W to E

2. Plateau rivers

-drain West into Atlantic (except Limpopo river which drains into Indian)

-shorter rivers at E drain down eastern escarpment

3. Escarpment

-borders plateau and separates it form coastal plains

-made of mountain ranges (Drakensburg)

-max. altitude = 1900m (eastern)

-lines entire coastline

4. Coastal plains

-narrower @ West

-wider @ east

5. cape fold mountains

- 2 mountain ranges that meet at Hex River mountains

6. Karoo basins

-Little Karoo: between 2 belts of cape fold

-Great Karoo: between cape fold and escarpment

cliffs (5)

-AKA scarp face/freeface

-almost vertical

-hard, resistant rock layer

-loose material falls off the cliff foot

-retreats parallel to itself (angle doesn't change)

crest (4)

-top of a hill

-convex shape

-thin layer of soil

-weathered material is removed

talus (3)

-AKA scree/debris slope

-uniform angle

-material from cliff and crest lands here

Pediment (3)

-low angle, concave slope

-steeper at talus, gentler at base

-increases as slope retreats backwards due to scarp retreat

knickpoint (2)

-not an official slope element

-marks a change in angle between talus and pediment

primary erosion slope

a slope developed from erosion of land due to air, water, ice, etc

secondary erosion slope

a slope developed from erosion of primary slopes

deposition slope

a slope formed from deposits of weathered material

gentle slope

a slope with a low angle

steep slope

a slope with a high angle

concave slope

a slope with a high angle at the top and a low angle at the base

convex slope

a slope with a low angle at the top and a high angle at the base

Significance of slopes for settlement (2)

-houses are built on slopes for views or due to limited space

-in the southern hemisphere, the North facing slopes are sunnier and warmer

Significance of slopes for agriculture (4)

-steep slopes = forestry

-gentle slopes = orchards and vineyards

-contour ploughing is needed to prevent soil erosion

-terracing can also be used when space is limited

Significance of slopes for recreation

steep slopes are good for hiking, climbing, etc

Significance of slopes for communication and transport (2)

-steep slopes are barriers to both (requires expensive passes to be built)

-roads are built to follow natural contours

climate as a factor affecting slopes (4)

-areas of high rainfall / melted water add volume and weight to soil

-increased rain = increases erosive ability of rivers at the base of slopes

-freezing and thawing causes soil to expand and contract = slope movement

-increased snow = increased slope movement

soil as a factor affecting slopes (2)

-little vegetation = unstable soil due to little binding

-soil movement is increased when soil is saturated

human influence as a factor affecting slopes (5)

-deforestation increases slope movement

-road construction + traffic vibrations compromise stability

-quarries and mining compromise stability

-building

-overgrazing and improper farming practises

rock type as a factor affecting slopes (2)

-resistant rock types erode slower and give stability

-less resistant rock = increased weathering and movement

peneplain

nearly flat plain formed by erosion of slopes on a humid environment

pediplain

a nearly flat plain formed as canyon floors widen in arid environments

Slope decline (5)

-based on European slopes

-humid climate

-slope is the steepest at the beginning and flattens over time due to water washing down the slope

-angle of slope increases until it becomes a peneplain

-slope becomes concave at the top and convex at the base

Slope replacement (5)

-based on andes and alps

-mountainous climate

-gentle and lower slopes erode backwards to replace high and steeper ones

-taluses collect at cliff foot = gentle slope

-central part becomes concave

scarp retreat (6)

-based on SA topography

-semi-arid climate

-angle of slope & slope elements remain constant

-slope moves backward parallel to its original position

-lower slope becomes concave

-pediment increases

exogenic force

forces which operate above the surface (erosion)

endogenic force

forces which operate deep underground (folding)