Earth’s Surface Processes: A Comprehensive Overview
1. Geomorphology
Geometry and Structure of Relief
Geomorphology aims to reconstruct Earth’s surface history and predict future changes. Landforms are a synthesis of past geological processes.
Morphometry
Morphometry studies landform parameters using mathematical procedures. Any landform can be broken down into simpler shapes, ultimately represented by slopes. This system classifies terrain based on geometric complexity. Morphometric mapping includes slope maps and other specialized maps.
Weathering and Soils
Weathering
Weathering involves the mechanical fragmentation or chemical alteration of rocks.
Physical Weathering
Rock fragments retain original material characteristics. Examples include:
- Gelifraction (Freeze-Thaw): Water expands upon freezing, causing rock fragmentation.
- Decompression: Igneous rock expands upon release of confining pressure.
- Thermal Expansion: Temperature fluctuations in deserts cause expansion and contraction.
- Biological Activity: Roots and acids from organisms contribute to weathering.
Chemical Weathering
This process breaks down rock components and mineral structures, forming new minerals. Water is the primary agent.
- Dissolution: Water dissolves minerals like halite.
- Oxidation: Responsible for iron oxide formation.
- Hydrolysis: Minerals react with water, forming reactive hydrogen and hydroxide ions.
Products of Weathering (Altérité)
- Saprolite
- Regolith
- Clay Waste
- Terra Rossa
- Arenizacion
- Oxides and Hydroxides
- Crete
Soils
Soil development depends on bedrock, weather, climate, vegetation, fauna, slope, and orientation.
Phases of Soil Evolution
- Initial surface formation from altered parent material.
- Vegetation establishment and weathering progression.
- Appearance of incipient C horizon.
- Appearance of incipient A horizon.
- Humification, material migration, and eluviation. Formation of B horizon.
- Consolidation of transfer phenomena and material movement. Formation of accumulation horizon.
- Land flattening and subhorizon formation.
Sediment
Sediment is unconsolidated weathered material transported and deposited elsewhere. It differs from soil in engineering terms.
2. Periglacial, Glacial, and Wind Sedimentation
Periglacial Environments and Processes
These environments are characterized by freeze-thaw processes and cold climate landforms.
- Permafrost: Permanently frozen ground except for a thin surface layer.
- Thermal Cycles: Freeze-thaw cycles in surface and subsurface water.
- Nival Coverts: Uncompacted snow masses that haven’t formed ice. They act as thermal insulators and can contribute to landslides.
Freeze-Thaw Processes
- Gelifraction: Material rupture by ice wedging.
- Swelling: Ground expansion due to volume changes.
- Mass Movement: Material movement on slopes.
- Cracking: Material breakage due to rapid heating and subsequent dehydration.
Periglacial Sediments and Landforms
- Surface: Slope wash, scree, talus.
- Surface: Mass movements like gelifluction, creep, and solifluction.
- Subsurface: Ice wedges, deformation, and turf hummocks.
Glaciers
Glaciers are dynamic ice masses formed from accumulated, compacted, and recrystallized snow. They accumulate, transport, and deposit sediment.
Glacier Movement (Flow)
- Plastic Flow: Internal ice deformation.
- Basal Slip: Meltwater lubricates ice movement over rock.
Glacial Balance
The balance between snow accumulation and loss (ablation) determines glacier advance or retreat.
Glacial Erosion
- Plucking: Meltwater freezes in rock cracks, fracturing the rock.
- Abrasion: Ice and rock debris smooth and polish underlying rock.
Glacial Transport
Glacial debris is called load, with large blocks termed erratics.
Glacial Sedimentation
Unconsolidated glacial sediments are called till, while consolidated till is tillite.
Wind Sedimentation
Wind Erosion
Deflation and abrasion (producing polished rocks).
Wind Transport
Dependent on clast size, shape, and wind speed.
Wind Sedimentation
- Dunes: Wave-shaped sediment accumulations.
- Loess: Fine particles transported long distances, forming deposits.
3. Hydrological Cycle, Surface Waters, Groundwater, and Karst Processes
The hydrological cycle describes water circulation between oceans, atmosphere, and continents, powered by solar energy.
Surface Water
Infiltration capacity influences the amount of water seeping into the ground. It’s controlled by:
- Precipitation intensity and duration
- Soil moisture
- Soil texture
- Slope
- Vegetation type
Streamflow
Channeled water flow, ranging from rivers to brooks.
Flow Types
- Laminar (smooth flow)
- Turbulent (rough flow)
Stream Erosive Capacity
Related to stream velocity, influenced by:
- Gradient
- Channel shape, size, and regularity
- Discharge
Longitudinal Profile
Cross-section from source to mouth, showing gradient and discharge changes.
Base Level
The lowest level a river can erode its bed.
River Erosion
- Clast removal
- Abrasion
- Dissolution
Sediment Transport
- In solution
- Suspension
- Bed load
Fluvial Sediments (Alluvium)
Sediment deposited by rivers, sorted by particle size.
Fluvial Terraces
- Eustatic
- Climatic
- Fluvioglacial
Watershed
Area contributing water to a stream, separated by watersheds.
Water Table
Upper limit of groundwater.
Groundwater
Factors Influencing Groundwater
- Porosity: Percentage of pore space.
- Permeability: Ability to transmit fluids.
Aquifers
Rock layers transmitting water freely.
Aquitards
Impermeable layers hindering water movement.
Karst Processes
Karst Landforms
- Exokarstic (Surface): Dolines, sinkholes.
- Endokarstic (Underground): Caves, speleothems.
Karst Landscape Evolution
Initial percolation creates discontinuities and caves. Later stages form karst plains with residual relief.
Karst Hydrological Functioning
- Zone of Aeration: Air-filled ducts, except during heavy rain.
- Fluctuation Zone: Alternately dry and saturated.
- Water Table Zone: Permanently water-filled cavities.
- Deep Water Table Zone: A subzone of the water table zone.