Geological Hazards and Risk Management: Volcanoes and Earthquakes

Classification of Risks by Origin

Risks, according to their origin, are divided into three main categories: natural, technological, and mixed.

Natural Hazards

Natural hazards are incidents defined by the internal and external dynamics of the Earth. They are further classified by their specific origin:

• Geological:
  • Endogenous: Associated with internal geodynamics (e.g., volcanoes, earthquakes).
  • Exogenous: Associated with external geodynamics (e.g., movements of hillsides, torrents).
• Meteorological (Weather): Caused by the action of the atmosphere (e.g., hurricanes, typhoons).
• Cosmic: Due to external phenomena (e.g., meteors, asteroids).
• Physical: Includes risks like natural fires and natural radioactivity.
• Biological: Risks caused by living organisms.

Technological and Mixed Risks

Technological Risks: Caused directly or indirectly by human activity.

Mixed Risks: Natural risks enhanced or amplified by human action.

Risk Management Concepts

Prevention

Prevention includes all possible measures taken in advance to mitigate, reduce, or avoid damage and the resulting consequences of a risk event.

Prediction

Prediction involves anticipating a phenomenon, such as a flood or an avalanche, by knowing the weather conditions that can foster it.

Endogenous Geological Risks

Volcanoes: Manifestation of Internal Energy

Volcanoes are the clearest manifestation of the release of energy generated by the movement of lithospheric plates. All volcanoes located on the shores of the Pacific Ocean form the Ring of Fire (or Belt of Fire), which is the most extensive and active set of volcanoes globally.

Hazards and Precursors Associated with Volcanoes

The primary hazards associated with volcanoes include:

• Lava flows that slide down the slopes.
• Pyroclastic flows (solid materials ejected violently or less violently).
• Volcanic ash.
• Toxic gases.

It is possible to detect anomalies that precede an eruption. These precursors include:

• Earthquakes of increasing magnitude and frequency.
• Appearance of fractures.
• Elevation of the soil and release of gases.
• Magnetic anomalies.
• Chemical changes in fumaroles and hot springs.

Earthquakes: Surface Vibrations

Earthquakes are vibrations of the Earth's surface due to the release of internal energy, resulting from the movement of plates, faults, shocks, or other processes inside the planet. They are generally divided into two types:

• Tectonic: Occur due to tears, cracks, and friction within the rock mass.
• Volcanic: Occur due to the movement of magma in deep soil layers or during volcanic eruptions.

Factors Affecting Earthquake Damage

One critical factor is the depth of the hypocenter (the place where the earthquake originates). The closer the hypocenter is to the surface, the greater the damage that occurs.

The destruction caused in populated areas depends not only on the magnitude of the phenomenon but also on:

• The distance to the epicenter.
• The type of buildings.
• The materials used for construction.
• The preventive measures implemented during construction.

Diapirs (Endogenous Risk)

Diapirs refer to geological structures formed when less dense rocky material rises through the overlying rock layers.