Geological Risks: Erosion, Volcanoes, Earthquakes, and Ground Movement
Geological Risks
Erosion
Erosion, a major manifestation of external geological activity, significantly alters landforms over time, sometimes dramatically changing landscapes. Various external geological agents contribute to erosion, including:
- Wind erosion
- Glacier erosion
- River erosion
- Marine erosion
Volcanoes
Prediction
- Return period and eruption type
- Volcanic precursors (tremors, topographical changes, electromagnetic and gravity anomalies, gas emissions, satellite-detected changes)
- Risk mapping
- Note: Explosive volcanism is difficult to predict.
Prevention
- Divert lava flows
- Construct water discharge tunnels for craters or boilers
- Restrict construction in high-risk areas
- Reduce reservoir levels
- Plan evacuations
- Build houses with sloping, fireproof roofs for protection against hot clouds
Earthquakes
Prediction
- Return period
- Seismic precursors
- Risk maps (probability and exposure)
- Localization of active faults (satellite and radar)
Prevention
Structural Measures
- Earthquake-resistant buildings (avoid overcrowding, symmetrical and rigid designs, diagonal buttresses, insulating foundations, flexible materials on soft soils, low-rise construction, flexible water and gas facilities)
Non-structural Measures
- Land-use planning
- Evacuation plans
- Education and risk insurance
Ground Movement
Geodynamic processes cause various ground movements, including landslides, subsidence, and flows.
Landslides
Gravitational mass movements of soil and/or rock on slopes. They can be rotational or translational.
Flows
Mass movements of soil behaving like a fluid, with continuous deformation and no defined fracture surfaces. Examples include clay flows (fast) and solifluction (slow).
Free Fall, Rolling, and Tipping
Sudden free falls of rock blocks, common in steep slopes, cliffs, and rock walls.
Creep
Very slow movement in the upper layers of clay slopes, caused by expansion and retraction.
Avalanches
Snow avalanches on steep slopes (normal, fusion, plate).
Sinkholes and Subsidence
Vertical ground movements. Subsidence refers to sudden movements, while subsidence refers to slow movements. Types include:
- Subsidence of underground cavities in rock
- Surface subsidence in rocks or soil
- Slow and gradual descent of the ground surface
Detachments Prevention
- Risk mapping
- Civil protection measures
- Slope modification
- Drainage systems (gutters, ditches, wells, galleries)
- Containment measures (walls, nets, anchors)
- Vegetation planting
- Anchoring unstable surfaces
- Marking landslide-prone areas