❄️Earth Surface Processes Unit 1 – Earth Surface Processes: An Introduction

Key Concepts and Terminology

• Geomorphology studies the physical features of the Earth's surface and the processes that shape them
• Endogenic processes originate from within the Earth (tectonic activity, volcanic eruptions)
• Exogenic processes originate from outside the Earth (weathering, erosion, deposition)
• Weathering breaks down rocks and minerals through physical, chemical, and biological processes
  • Physical weathering involves mechanical breakdown (frost wedging, salt crystallization)
  • Chemical weathering alters the composition of rocks (dissolution, oxidation, hydrolysis)
• Erosion is the removal and transport of weathered material by agents such as water, wind, and ice
• Deposition occurs when transported sediment settles out of the moving medium (water, wind)
• Geomorphic thresholds represent critical points at which landforms undergo significant change (slope failure, channel incision)

Earth's Surface Systems Overview

• Earth's surface is a complex system shaped by the interaction of various processes and factors
• Tectonic processes create topographic relief through uplift, subsidence, and deformation
• Climate influences weathering rates, vegetation cover, and the intensity of surface processes
  • Humid climates tend to have higher weathering rates and denser vegetation
  • Arid climates have lower weathering rates and sparse vegetation
• Lithology (rock type) affects the susceptibility of rocks to weathering and erosion
  • Resistant rocks (granite, quartzite) weather and erode more slowly than weak rocks (shale, limestone)
• Hydrology plays a crucial role in shaping the Earth's surface through the action of rivers, glaciers, and groundwater
• Biological processes, such as plant root growth and animal burrowing, contribute to weathering and soil development

Major Geomorphic Processes

• Fluvial processes involve the action of running water, primarily in rivers and streams
  • River channels erode, transport, and deposit sediment, creating features like floodplains and terraces
• Coastal processes shape shorelines through the action of waves, tides, and currents
  • Waves erode cliffs, transport sediment, and build beaches and barrier islands
• Glacial processes occur in areas where ice accumulates and flows under its own weight
  • Glaciers erode bedrock, transport debris, and deposit sediment in moraines and outwash plains
• Aeolian processes involve the action of wind in arid and semi-arid environments
  • Wind erodes, transports, and deposits sediment, creating features like dunes and loess deposits
• Mass wasting processes involve the downslope movement of rock, soil, and debris under the influence of gravity
  • Examples include rockfalls, landslides, and debris flows

Weathering and Erosion Basics

• Weathering is the breakdown of rocks and minerals at or near the Earth's surface
• Physical weathering processes include:
  • Frost wedging: water freezes and expands in rock cracks, causing the rock to split
  • Salt crystallization: salt crystals grow in rock pores, exerting pressure and causing the rock to disintegrate
  • Thermal expansion and contraction: temperature changes cause rocks to expand and contract, leading to cracking
• Chemical weathering processes include:
  • Dissolution: minerals dissolve in water, particularly in acidic conditions (limestone in karst landscapes)
  • Oxidation: minerals react with oxygen, often producing rust-colored iron oxides (red soils in tropical regions)
  • Hydrolysis: minerals react with water, leading to the formation of clay minerals
• Erosion is the removal and transport of weathered material by agents such as water, wind, and ice
  • Water erosion includes sheet wash, rill erosion, and gully erosion
  • Wind erosion is most effective in arid environments with sparse vegetation cover
  • Glacial erosion occurs through plucking and abrasion of bedrock by ice and debris

Sediment Transport and Deposition

• Sediment transport occurs when weathered material is moved by water, wind, or ice
• The capacity of a medium to transport sediment depends on its velocity and turbulence
  • Faster and more turbulent flows can transport larger and heavier particles
• Fluvial transport includes:
  • Suspension: fine particles are carried within the water column
  • Saltation: particles bounce along the riverbed
  • Bedload: particles roll or slide along the riverbed
• Aeolian transport involves the movement of sand and dust particles by wind
  • Suspension: fine particles are carried high in the air and can travel long distances
  • Saltation: sand grains bounce along the surface
  • Creep: larger particles roll or slide along the surface
• Deposition occurs when the transport medium loses energy and can no longer carry its sediment load
  • Fluvial deposition creates features like floodplains, deltas, and alluvial fans
  • Aeolian deposition forms dunes, loess deposits, and desert pavement

Landform Development

• Landforms are the physical features of the Earth's surface, such as mountains, valleys, and plains
• Landform development is influenced by the complex interaction of tectonic processes, climate, lithology, and surface processes over time
• Tectonic processes create topographic relief through uplift, subsidence, and deformation
  • Uplift can lead to the formation of mountains, plateaus, and escarpments
  • Subsidence can create basins, rift valleys, and coastal plains
• Climate controls the intensity and distribution of weathering, erosion, and vegetation cover
  • Humid climates tend to produce rounded, soil-mantled landforms (rolling hills)
  • Arid climates often result in angular, bare-rock landforms (mesas, buttes)
• Lithology influences the susceptibility of rocks to weathering and erosion, leading to differential erosion
  • Resistant rocks form ridges, cliffs, and peaks (granite mountains)
  • Weak rocks form valleys, lowlands, and badlands (shale badlands)
• The interplay of surface processes over time shapes the evolution of landforms
  • River incision and lateral erosion create valleys and canyons
  • Glacial erosion produces U-shaped valleys, cirques, and arêtes
  • Coastal processes form cliffs, beaches, and barrier islands

Human Impact on Surface Processes

• Human activities have significantly altered Earth's surface processes and landforms
• Urbanization and infrastructure development modify natural drainage patterns and increase surface runoff
  • Impervious surfaces (roads, buildings) reduce infiltration and increase flood risk
  • Stormwater management systems (gutters, drains) concentrate and accelerate runoff
• Agriculture and deforestation expose soils to increased erosion by removing protective vegetation cover
  • Tillage and plowing disrupt soil structure and increase vulnerability to wind and water erosion
  • Overgrazing by livestock reduces vegetation cover and compacts soils
• Mining and quarrying activities directly alter landforms and expose large volumes of unconsolidated material to erosion
  • Strip mining removes entire layers of rock and soil, creating vast open pits
  • Tailings and waste rock piles are highly susceptible to erosion and can pollute nearby waterways
• Dams and river regulation modify natural flow regimes and sediment transport
  • Dams trap sediment in reservoirs, reducing downstream sediment supply
  • Altered flow patterns can lead to channel incision, bank erosion, and changes in floodplain dynamics
• Coastal development and engineering structures interfere with natural coastal processes
  • Seawalls and groins disrupt longshore sediment transport, leading to erosion and accretion
  • Dredging and beach nourishment alter the balance between sediment supply and removal

Practical Applications and Case Studies

• Geomorphological knowledge is essential for sustainable land management, hazard assessment, and infrastructure planning
• Soil erosion control measures, such as terracing, contour plowing, and cover cropping, help to reduce soil loss in agricultural areas
  • Terracing reduces slope length and gradient, minimizing runoff and erosion
  • Contour plowing aligns furrows with elevation contours, slowing down runoff
• Landslide hazard assessment and mitigation rely on understanding the factors that control slope stability
  • Identifying potential landslide triggers (heavy rainfall, earthquakes) and susceptible areas (steep slopes, weak rock layers)
  • Implementing stabilization measures (drainage, retaining walls, slope regrading)
• River restoration projects aim to restore natural channel dynamics and improve ecological function
  • Removing obsolete dams and allowing rivers to regain their natural flow patterns
  • Reconnecting floodplains and creating wetlands to reduce flood risk and enhance habitat
• Coastal management strategies balance the needs of development, recreation, and natural processes
  • Implementing setback lines and zoning regulations to minimize development in erosion-prone areas
  • Using soft engineering approaches (beach nourishment, dune restoration) to maintain coastal defenses
• Geomorphological studies inform the design and construction of resilient infrastructure
  • Assessing the long-term stability of dam and reservoir sites
  • Designing bridges and culverts to accommodate changes in river channel morphology
  • Planning transportation corridors to minimize the impact on natural drainage patterns and landforms