Volcanic Risks and Prevention: A Detailed Analysis
Volcanic Risk
Volcanoes are cracks on the Earth’s surface where magma flows out from deep within the Earth. Volcanic eruptions can have both negative and positive influences. Volcanoes have historically provided fertile land, mineral resources, and geothermal energy. The number of direct victims is not very high, but there can be significant economic losses.
Volcanic Products
- Gases: Primarily water vapor, CO2, N2, and H2S.
- Liquids: Lava.
- Solids: Pyroclastics.
Volcano Location
Volcanoes have a very close relationship with tectonic plates, especially at plate edges, both constructive and destructive. They can also be found associated with intraplate volcanic magmatism, normally related to failures.
Major Volcanic Risk Factors
- Quantity of humans living near the volcano: As the population increases, the exposure factor increases.
- Type of volcanic eruption:
- Basic magmas are poor in silica (SiO2) and fluids, resulting in quiet, effusive eruptions. The speed of these lavas makes them dangerous.
- Acid magmas are rich in silica and viscous, resulting in explosive eruptions. The greater the quantity of gases in the magma, the more explosive the eruption will be. A single volcano can have different types of eruptions.
- Rain of pyroclastics: Depending on the number and size, pyroclastics can cause serious damage. Ash, being lightweight, can travel many kilometers, causing suffocation and the collapse of buildings.
- Burning clouds: Gases at high temperatures (600-800°C) mixed with ash roll downhill, threatening lives.
- Associated Risks:
- Phreatomagmatic eruptions, caused by magma-heated water.
- Mudflows or lahars, formed by melting ice and snow.
- Tsunamis: Tidal waves up to 30 meters high that can penetrate up to 10 kilometers inland.
- Slope movements, landslides, and blockages of valleys.
- Emission of poisonous and asphyxiating gases (SOx, HF, etc.).
- Fires caused by the destruction of gas pipelines or electrical lines.
Monitoring and Preventing Volcanic Hazards
Prediction relies on the history of a volcano. Surveillance is normally concentrated on volcanoes that have been inactive for a long time. Precursors or signs of activity, such as small earthquakes (seismographs), ground elevations (inclinometers and theodolites), analysis of emitted gases, and changes in the electrical potential of rocks, are studied. It’s possible to tell when a volcano is going through an abnormal phase, but not when or how the final eruption will occur. The usual prevention systems consist of diverting lava flows away from inhabited places and constructing water discharge tunnels for lahars. It’s necessary to secure land and property, define living areas, and carry out evacuations.
Volcanic Risk in Spain
Examples of volcanism in Spain are found in the Canary Islands and on the peninsula at Cape Gata (Almería), Olot (Girona), and Campo de Calatrava (Ciudad Real). However, the only historically active volcanism with confirmed dates is in the Canary Islands: Lanzarote (1831), Tenerife (1909), and La Palma (Teneguía volcano, 1971). The Canary Islands’ volcanism is of the intraplate type and is linked to the Alpine orogeny, not to hot spots.
Volcanic Risk in Murcia
The volcanism in the Region of Murcia developed in two main stages:
- First Stage: The most important stage due to the abundance and variety of materials. It developed between -17 million years ago, resulting in rocks of the following types:
- Calc-alkaline rocks, represented only in Cape Gata (Almería).
- Potassium-rich shoshonitic calc-alkaline rocks, well represented in Mazarrón-Mar Menor.
- Ultrapotassic rocks (lamproites), present in much of the province of Murcia, north of the Cartagena-Mazarrón line.
- Second Stage: After a pause of 2 million years (-6 to -4 million years ago), the second stage occurred, leading to emissions of small alkaline basalts. These outcrop near Cartagena.