Explain, with the aid of a diagram(s), how volcanic eruptions occur. - Leaving Cert Geography - Question Question - 2011

Volcanic eruptions begin with the formation of magma, which occurs within the Earth's mantle due to the melting of rock caused by high temperatures and pressures. This magma is less dense than the surrounding rock and rises through the crust.

As magma rises, it accumulates in the magma chamber found beneath the volcano. Over time, gases dissolved in the magma (including water vapor, carbon dioxide, and sulfur dioxide) begin to expand, creating immense pressure within the chamber.

The increasing pressure causes the surrounding rock to fracture. These fractures form pathways for the magma to escape, known as vents.

When the pressure within the magma chamber becomes too great, an eruption is triggered. This can happen suddenly, often resulting in explosive eruptions, or more gradually, leading to effusive eruptions where lava flows steadily from the vent.

Eruptions can be categorized into two primary types: explosive eruptions, which release a large amount of ash and gas, often leading to pyroclastic flows, and effusive eruptions, characterized by the smooth flow of lava that may form lava tubes or mounds.

After an eruption, the landscape may be altered significantly, with new landforms created from lava deposits and pyroclastic materials. Additionally, volcanic ash can affect climate and air quality.