Understanding Volcanic Activity and Other Natural Hazards
Risks Associated with Volcanic Activity
Explosions of the Volcano: This occurs when highly viscous magma causes violent explosions, ejecting clouds loaded with liquid magma fragments and solid rock fragments from the vent, or recently formed rocks. These rocks form a cloud called a pyroclastic flow, which moves at high speed down the slopes, dragging everything in its path.
Rain of Pyroclastic Materials: In volcanoes that eject a large amount of fine material, the material is entrained by the exiting gases (called pyroclastic material). This produces vertically developed clouds. Depending on the height of the column and the wind’s direction and strength, a large amount of material will fall to the ground in more or less extensive areas, destroying vegetation, collapsing roofs and buildings, and even burying entire cities, such as Pompeii.
Lava Flows: When the lava is very fluid, it can form rivers of lava flowing along the slope as if it were a real river. These are not too dangerous, but everything in their path is destroyed due to their high temperature.
Lahars: These are mudflows formed when snow melts quickly due to the eruption or heavy rains, which sweep away pyroclastic material.
Gaseous Emissions: The most abundant gas is water vapor, but significant concentrations of CO2, CO, SO2, and SO may appear, which can be expelled suddenly and are very toxic to humans, animals, or plants. To avoid possible damage caused by volcanic eruptions, the following measures have been established:
Prediction Mechanism: It is necessary to know the history of each volcano and its eruptions, both in intensity. A point should be made of those volcanoes in volcanic areas that can be assumed are not off, as they tend to show a number of indications related to the output of magma, degassing, and eruptive mouths.
Methods of Prevention and Correction: The principal action is planning, defining the areas of human settlements. Due to the high productivity of volcanic terrains, these areas have a high population density. The only defense against an eruption is population evacuation, but crops, homes, and property will be lost.
Risks Associated with Gravitational Processes
Landslides
Slips: These are movements of soil or rock mass along slopes, favored by the fracture of the underlying surface on which they rest, called the failure surface, and the force of gravity.
The two factors that increase the risk of slippage are the slope of the land and water, which soaks the materials, increases weight, and decreases the friction force of the fracture surface.
There are two fundamental aspects:
- The possibility of hitting moving materials, depositing or burying people, buildings, crops, etc.
- The fact that the spot on which these people settle, infrastructure moves down the slopes.
To avoid the risk associated with landslides, the most important thing is to avoid settlements, both on the surface of unstable places and at their base. In the case of already installed settlements, it will be necessary to stabilize the land and install drains to remove water and other engineering measures.
Landslides
Landslides: These consist of the fall of blocks of different sizes from the highest part of a slope to the bottom, from broken fields. The action of temperature changes, rain, and other weathering can fracture rocks. They are common in mountainous areas of communication pathways, which can lead to accidents. In the case of urban areas, they can be disastrous.
Avalanches
Avalanches: These are rapid movements of land masses or lumps of rock, sometimes accompanied by ice and snow, called avalanches. Their effects are unpredictable and very devastating when a consequence of an earthquake or volcanic explosion.
Weather and Climate Risk
Floods
Floods: These are the result of the overflow of river channels or other natural resources due to rainfall that protrudes from the channels. They are also produced by rising sea levels caused by very intense waves. Heavy rains are an atmospheric phenomenon that is part of the normal dynamics of the geosphere but becomes a risk because of the proximity of most populations to streams or near the sea.