Understanding Natural Hazards: Floods, Earthquakes, and Fires

Natural Hazards

Floods

Floods are common hazards often caused when heavy rainfall exceeds the soil's absorption capacity, leading to surface runoff. Aquifers, which are bodies of water found below ground, may be circulating or remain stagnant.

The risk of flooding depends on two factors:

• Precipitation type: There is a major risk if too much water falls in a short time.
• Orography of the land: The danger increases in low-lying areas and decreases at higher elevations. Thus, we predict that low areas (valleys) in regions with heavy rainfall are at higher risk.

Flow rate: This is the maximum level of water a river can reach during periods of peak precipitation. In these circumstances, the river overflows its banks, flooding the surrounding areas.

Crustal Movements

The outermost layer of the Earth is the lithosphere, which is divided into plates that move slowly. These movements generate forces of compression and distortion that can be released suddenly, causing catastrophes.

Earthquakes

These are strong vibrations of the ground that can sometimes cause buildings to collapse, becoming very dangerous. Border areas of lithospheric plates are the places on Earth where the risk is highest.

Tsunamis

These are caused by movements of the crust in areas covered by the sea or close to it. These crustal movements create tidal waves that travel hundreds of miles. They can cause huge disasters in coastal areas, as these large waves can penetrate several kilometers inland.

Volcanoes

Volcanoes are formed when a fissure in the Earth's crust allows hot molten material to reach the surface. In some volcanoes, the lava is very fluid and flows gently down the slope, making them the least dangerous. In other cases, the volcano violently ejects pyroclasts and ash, which are very dangerous hot clouds.

Forest Fires

These occur in areas with abundant natural vegetation. Fire may result from natural causes (lightning) or human activity (accidental or intentional). By eliminating one of the three elements in the fire triangle, the fire is extinguished.

Conditions conducive to fires:

• Environmental dryness
• High temperatures
• Wind

Once a fire has started, extinction efforts begin using terrestrial resources (firefighters, forestry equipment) and air support (planes, helicopters). Fires can cause diverse damage, and they are especially dangerous when affecting human constructions. After a fire, the affected area is devoid of vegetation, making it vulnerable to erosion (soil loss). Ecological recovery of these areas is usually a long-term process.