Part 2

• The Drakensberg Escarpment is the central eastern and highest portion of the Great Escarpment in southern Africa, reaching up to 3482 masl
• The Great Escarpment


  • Separates coastal lowlands and fold mountains from the high plateau and semi-arid river systems of the interior
  • Represents differences in topography, geomorphology, climatic, and ecologic systems
  • Distinct landscapes and evolutionary patterns
• Drakensberg Escarpment


  • Outward facing near-vertical scarps reaching 600 m high
  • Varied temperature and precipitation regimes between footslope and scarp edge locations
  • Precipitation ranges from 1,600mm (eastern escarpment) to less than 600mm (rain shadow zone)
  • Temperature range of mean annual 5-6°C, seasonal -10°C to 0°C
  • Frost days range from 30-40 days (foothills) to over 120 days (high mountain valleys)
  • Supports alpine flora and a marginally periglacial physical setting
• The escarpment landscape development is strongly influenced by its physical properties and shaped by weathering, periglacial/glacial, mass movement, and fluvial processes, especially during the Quaternary Period
• The escarpment experiences climate change and human activity, posing challenges to its geomorphology and geo- and bio-conservation
• Geological Setting


  • The Karoo Supergroup sedimentary rocks are overlain by the Drakensberg Group volcanic lavas, forming a basaltic capping approximately 1,500 meters thick
  • Basalt flows in the lavas are almost horizontally layered, with thickness ranging from 3 to 8 meters
  • Weathering rates, processes, and landform development are influenced by contrasting lithology, age, and formation mechanisms
  • Denudation and land surface erosion occurred episodically during the Cenozoic period (~66 Ma)
  • Evidence of erosion includes exhumed igneous rocks, preserved paleo-surfaces, and apatite fission track thermochronometric dating suggesting erosion rates of 95 ± 43 ,/Ma between 91-69 Ma
  • Phases of tectonic uplift were followed by land surface denudation, forming regional-scale planation surfaces like the African Surface, Post-African I Surface, and Post-African II Surface
• Landscape & Climate Dynamics during Quaternary and Holocene

  • Shifts in atmospheric circulation caused temperature decreases of 5-7°C relative to present during the Last Glacial Maximum (~20,000 years ago)
  • Significant climate variability between adjacent summit and valley sites due to high relief
  • Regional climate patterns may not always describe the microscale climates
  • Sedimentary sequences preserved in valley heads and colluvial mantles have yielded oldest 14C ages of 13,500-43,000 years ago
  • Colder/drier periods (Little Ice Age) resulted in greater snow cover, higher albedo, sporadic permafrost, seasonally frozen ground, and temperatures 2-3°C lower than present
• Rock Weathering Phenomena in the Drakensberg

  • Evidence of long-term weathering includes weathered igneous rocks up to 25 meters deep, corestones with exfoliation attributes, pseudokarst weathering pits, fractured bedrock scarp edges, and freshly exposed fractured bedrock material due to lightning strikes
  • Weathering and downslope sediment transport contribute to the formation of relatively bare upland surfaces with scattered remanié boulders
• Weathering features in the high Drakensberg

  • Corestones produced by subsurface chemical weathering
  • Pseudokarst surface weathering pits found on basalt outcrops
  • Fractures developed around basalt scarp edges
• Geomorphology


  The study of the physical features of the earth's surface and their relation to its geological structures and history
• GEOG211


  2024
• Rock Weathering Phenomena in the Drakensberg

  • Weathered igneous rocks up to 25 meters deep
  • Corestones with exfoliation attributes
  • Formation of pseudokarst weathering pits on exposed basalt and sandstone surfaces
  • Fractured bedrock scarp edges resulting from mechanical and chemical weathering
  • Freshly exposed fractured bedrock material due to lightning strikes
• Weathering and downslope sediment transport in the Drakensberg


  • Formation of relatively bare upland surfaces with scattered remanié boulders
• Periglacial and Glacial Features in the Drakensberg


  • Currently only marginally periglacial
  • Characterized by earth hummocks (thufur) and microscale sorted stone circles
  • Permanent snowbanks and niche/cirque glaciers in topographically favorable locations during the Late Quaternary
  • Evidence of ice-marginal moraines
• Past Periglacial Activity in the Drakensberg

  • Large stone circles (>1 m diameter)
  • Stone-banked lobes
  • Solifluction lobes
  • Block streams
  • Development during cooler and potentially more humid periods, last glaciation and possibly the Little Ice Age
• Mass Movements in the Drakensberg

  • Rockfalls typically originating near the summit edge
  • Rockfalls potentially evolving into rock slides and triggering dry debris flows on the lower flanks
  • Surficial slides and flows, slides with a prominent shear zone transforming into flows
  • Occasional translational and rotational landslides and mudflows, occurring through the basalt into the underlying Clarens Formation
  • Landslide events near the Drakensberg margins during the Late Quaternary/Early Holocene, resulting in the obstruction and diversion of river valleys
• Fluvial Landforms in the Drakensberg

  • Tectonic uplift of the Great Escarpment region leading to changes in river head-cutting and drainage diversion
  • Rivers in mountain valleys exhibiting frequent flash floods and episodic bedload transport
  • Terraces, abandoned bars, and small floodplains primarily formed through fluvial reworking of slope-derived materials
  • Elongated gravel bars formed in adjacent river channels, indicating the significant influence of high-energy flood events on sediment erosion and deposition patterns within mountain catchments
• Present Day Management of the Drakensberg

  • Part of the uKhahlamba/Drakensberg Park World Heritage Site, recognized for its exceptional topography, high biodiversity, endemic species, and San rock art
  • Protected as part of the Maluti-Ukhahlamba/Drakensberg Transfrontier Conservation Area
  • Issues include overgrazing and soil erosion, construction of new roads/dams/quarries, planned developments, and ongoing climate change
• The geomorphological evolution of the Drakensberg escarpment was influenced by both geological and climatic factors throughout the Cenozoic era
• Initial volcanic and plate tectonic events played a significant role in shaping the landscape of the Drakensberg region
• Changes in climate and environmental conditions during the Late Quaternary resulted in the formation of prominent paleo-landforms in the high Drakensberg
• Denudation rates (erosion and weathering) provide macroscale source materials for microscale processes such as weathering, slope sediment transport, mass movements, periglacial processes, and fluvial systems
• Human-induced activities have had a significant impact on the Drakensberg landscape, leading to widespread gully erosion and increased aeolian (wind-driven) processes, exposing the surface to contemporary landform development such as turf exfoliation and formation of pans
• SU8 - Fluvial Geomorphology of Southern Africa (Part 1), Chapter 3 and Chapter 8 of Grab and Knight, 2015


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