Volcanic eruptions are incredibly powerful geological events that can have devastating impacts on the land, people, and environment around them. In this article, we will explore the causes of eruptions, the different types of eruptions, and their impacts as we better understand the incredible forces of nature at work.
Eruptions are caused by the release of pressure created by the formation of magma within the Earth’s crust. Magma is produced when existing rock material melts as a result of extreme temperatures and pressures created by the movement of tectonic plates. This molten material is known as magma and is often mixed with dissolved gases such as water vapor, carbon dioxide, and sulfur dioxide. When the pressure beneath the surface becomes too great, magma is released in the form of an eruption. Additionally, earthquakes caused by the movement of tectonic plates can also create magma pockets and cause eruptions.
The underlying causes of these plate movements vary depending upon the type of plate boundary. At divergent boundaries, new crust is formed as lava oozes out into the open space. Similarly, convergent boundaries can also lead to eruptions, as the denser plate is forced down into the mantle amid intense heat, melting both plates and producing magma in the process. Transform boundaries can also trigger eruptions, as these boundaries cause friction between two plates, resulting in earthquakes and pressure buildup.
Volcanic eruptions occur when magma finds a path to the surface and erupts from a volcanic vent. During an eruption, the pressure of the magma is so great that it blasts through the air and rock above it, releasing ash and gas into the atmosphere and creating volcanic debris. The intensity of the eruption is determined by a number of factors, including the type of magma, the shape of the magma chamber, and the size of the magma chamber.
Types of eruptions are differentiated by both their magnitude and the type of material emitted. At the most basic level, eruptions are classified as either effusive or explosive. Effusive eruptions, such as lava flows and fissure eruptions, produce magma composed of basaltic elements that cool quickly after being ejected. These eruptions generally reach temperatures of 1,100-1,200°C and have relatively low gas content. Conversely, explosive eruptions, such as those which occur along plate boundaries, are characterized by a high gas content and can reach temperatures of up to 2,000°C. These eruptions tend to be significantly more destructive, as they can cause widespread devastation in the form of pyroclastic flows and tephra falls.
Types of eruptions also vary in their magnitude, which is measured using the Volcanic Explosivity Index (VEI). This index measures the volume of material released during an eruption, ranging from VEI 0 (non-explosive) to VEI 8 (mega-colossal) for the largest eruptions ever recorded. In general, VEI 0-2 eruptions are described as "gentle," VEI 3-4 are categorized as "explosive," and VEI 5-8 eruptions are labeled as "catastrophic." Although higher VEI eruptions tend to be more destructive, there are exceptions to this rule. For instance, some VEI 4 eruptions have caused significant amounts of damage while other VEI 8 eruptions have only produced local disturbances.
Volcanic eruptions can have a wide range of impacts. Most notably, the direct impacts are on people and the environment, as well as structures, land and property. The indirect impacts can be economic, social, cultural and psychological.
When an eruption occurs, it can cause significant disruption to human life, both directly and indirectly. Directly, people may be injured or killed due to explosions, ashfall, lava flows, mudflows, falling rocks and gases like carbon dioxide and sulphur dioxide. Indirectly, the disruption can come in the form of long-term changes to the environment and agricultural land, damage to infrastructure, disruption to transportation systems and loss of livelihoods.
The effects of an eruption can also be felt socially and culturally. People may be displaced from their homes, disrupting their traditional way of life. Psychological impacts can be wide ranging, including trauma and post-traumatic stress disorder. Additionally, the economic impacts of volcanic eruptions can be catastrophic, affecting tourism, agriculture, fisheries and other industries.