Geological Hazards and Hydrological Phenomena Explained

1. Gravitational Slope Movements

a. This is a gravitational slope movement, which may involve complex slides, rotational slides, or a combination of other slope phenomena.

b. Two primary determinants include:

• Lithological: The presence of weathered surface materials, lack of cohesion, and the depth of various rock strata.
• Structural: The orientation of bedding planes relative to the slope surface and the presence of fractures or faults.

Additionally, anthropogenic factors, such as vegetation changes, may contribute to slope destabilization.

2. Hydrograph Analysis

a. A hydrograph represents flow variation over time in a stream.

• Annual hydrograph: Represents average flow changes throughout the year.
• Flood hydrograph: Essential for assessing flood events.

b. Both hydrographs show a maximum flow of 3000 m³/s. In scenario A, the flood is slower, peaking around day 13 before decreasing gradually. In scenario B, the flood is rapid, reaching a maximum at noon with a sharp decline. In the second hydrograph, initial and final flows are minimal.

3. Earthquakes: Magnitude and Intensity

a. Earthquake magnitude measures the energy released and the degree of movement, typically assessed using the Richter scale. Intensity measures the capacity for destruction and vulnerability, assessed using the Mercalli scale (graded I to XII).

b. Factors increasing mortality and structural damage include:

• High magnitude.
• Long duration and frequent aftershocks.
• Poor construction quality.
• Secondary consequences like gas pipeline ruptures and fires.

c. Mitigation measures:

• Structural: Using resistant materials like steel or stone and avoiding construction near unstable slopes.
• Non-structural: Spatial planning and risk education.

4. Climate and Hydrosphere

a. The El Niño phenomenon is a fluctuation coupled between the atmosphere and the southern Pacific Ocean. Normally, trade winds push surface waters west, allowing cold, nutrient-rich water to surface near Peru. El Niño occurs due to overheating every 3–5 years, typically lasting 9–12 months.

b. The hydrosphere acts as a thermal regulator. Due to its high specific heat, water absorbs and stores heat energy, causing oceans to warm and cool more slowly than continents. Consequently, coastal regions experience lower temperature ranges than inland areas.