South Africa's Topography

• SA's topography includes a mean altitude of 1200 meters above sea level
• Approximately 40% of the land is at a higher elevation
• Parts of Johannesburg are more than 1800 meters above sea level

Interior Plateau

• SA contains a mainly flat interior at approximately 1000m above sea level

Plateau Rivers

• Plateau Rivers drain westwards toward the Atlantic Ocean
• The Limpopo River is the only river on the plateau to flow eastwards into the Indian Ocean

Coastal Plain

• The Coastal Plain is narrow on the western side and wide on the eastern side.
• The coastal plain extends from the Namibian border along the coast to Southern Mozambique

The Escarpment

• The escarpment separates the interior from the low lying coastal plain
• The escarpment runs the entire edge of the Southern African coastline.
• Along the eastern side, the escarpment is 1900m above sea level
• The escarpment in KZN forms the Drakensberg Range, separating KZN from Lesotho

The Great Karoo

• The Great Karoo Basin occurs from 1400 - 1600 meters

Eastern Rivers

• Eastern Rivers are shorter and drain down the eastern escarpment

Other Features

• The southwestern fold mountains influence the climate and vegetation patterns of the southern Cape
• The land rises steadily from west to east to the Drakensberg Mountains to a height of more of 3408 meters
• The escarpment on the western side only reaches a height of 1000m above sea level

Types of Slopes

• Slopes are curved, inclined surfaces that form the boundaries of landforms like mountains, plateaus, and hills

Concave Slope

• Forms when the top layer of rock is more resistant to erosion than the underlying rock
• Forms when intruding sills are exposed by erosion
• Steepness increases from the foot upwards

Convex Slope

• Common in humid areas, forming more rounded landscapes
• Forms when massive igneous rock intrusions are exposed by erosion

Stepped Slope

• Occurs in areas where alternating rock layers are present
• Resistant rock layers form the cliffs
• Less resistant rock layers form the gentler slopes
• Common in areas where layers of intruding sills are exposed

Vertical Slope (cliff)

• Formed by a layer of resistant rock
• Erosion of the cliff face results in the retreat of the cliff
• Eroded rocks fall to the base of the cliff

Slope Elements

• Landscapes formed by horizontally layered rocks, can have slopes with four parts

Crest

• Convex in shape
• Weathered material falls over the cliff
• Soil creep occurs

Cliff

• Also referred to as free face i.e. scarp slope
• Vertical bare rock
• Resistant rock erodes slowly, forming the cliff
• The cliff retreats backward due to erosion

Talus

• Also called the scree or debris slope
• Weathered material from the cliff and crest land on this slope
• The angle of the slope is uniform
• Finer materials are washed out onto the pediment
• Scree is loose eroded material from the cliff that collects on the talus slope

Pediment

• It has a gentle slope
• Covered with sediment from the talus slope
• Deeper soils due to a gentler angle

Knickpoint

• A knickpoint is a change in gradient

Slope Development: Slope Decline

• The slope is steepest to begin with
• Flattens over time
• Angle of the slope decreases
• The slope is convex in the upper part and concave along the lower parts

Slope Development: Slope Retreat

• Angle of the slope remains constant over time
• Slope elements remain over time
• The slope retreats backwards parallel to its previous position
• Lower parts of the slope are concave
• Pediment widens over time