Geological Processes and Natural Hazard Management

Geological Processes and Paroxysmal Phases

Most geological processes occur gradually and are not dangerous. However, paroxysmal phases occur when the magnitude is higher than usual, releasing a large amount of energy and covering a large spatial extension.

External Geological Processes and Weathering

External geological processes occur on the superficial lithosphere. They depend on solar energy potential and become active agents on the terrain. Weathering is the process by which rocks are physically or chemically altered, such as through mechanical disintegration or variation in composition.

Internal Geological Processes and Plate Tectonics

Internal geological processes are driven by geothermal energy. The geothermal gradient is approximately 1°C for every 33 meters of depth. This heat and energy are released during the radioactive nuclear disintegration process in cortical rocks, which is also responsible for the displacement of geological plates.

Understanding Geological Risks

Any condition or natural geological process that can generate harm to any human community is a product of three factors: hazard, vulnerability, and exposure.

Classification of Geological Risks

• Internal: Volcanoes and earthquakes.
• External: Floods, hillside movements, or quarries.
• Mixed: Soil erosion or the disappearance of beaches.
• Induced: Inundations due to dam breaks or water pollution from waste and exploitation.

Volcanic Risks and Their Impact

Volcanic risks are mostly found at plate limits, but intraplate areas also exist, such as Hot Spots. These occur due to thermal plumes where hot material rises from the lower mantle. As the plate moves, the lithosphere can rise above sea level, causing the formation of an island.

Factors of Volcanic Risk

• Exposure: Land tends to be overpopulated due to fertile soils and geothermal energy resources. This population agglomeration makes the potential disaster greater.
• Vulnerability: This depends on the means available to address the risks.
• Dangerousness: This depends on the size or type of eruption, geographical distribution, and return period.

Manifestations of Volcanic Eruptions

Their manifestations are as follows:

• Gases: The motor of eruptions; they expand and reach the exterior of the lithosphere, allowing the fracturing of other materials. They cause respiratory distress and suffocation.
• Lava Flows: These destroy crops and cause fires. Their danger depends on viscosity:
  • Acidic: High silica content, very viscous, releasing many dangerous gases and generating violent explosions.
  • Basic: Low silica content, slightly sticky, with low danger.
  • Pillow Lava: Abundant in submarine eruptions with high fluidity.