What indicators can suggest an imminent volcanic eruption?

Indicators of an imminent volcanic eruption include increased seismic activity, gas emissions, ground deformation, and changes in hydrothermal activity.

Seismic activity is one of the most reliable indicators of an upcoming volcanic eruption. As magma rises to the surface, it causes the surrounding rocks to crack and break, resulting in earthquakes. These earthquakes can range from minor tremors that are barely noticeable to major quakes that can cause significant damage. Scientists monitor seismic activity around volcanoes using seismographs, and a sudden increase in the frequency and intensity of earthquakes can be a sign that an eruption is imminent.

Another key indicator is the emission of gases. As magma rises, it releases gases that were previously dissolved within it. These gases, which include water vapour, carbon dioxide, and sulphur dioxide, can be detected by sensors and can provide valuable information about the state of the volcano. For example, an increase in sulphur dioxide emissions can indicate that new magma is rising to the surface.

Ground deformation is another important sign of an impending eruption. As magma accumulates in the magma chamber beneath the volcano, it can cause the ground to swell and deform. This deformation can be detected using a variety of techniques, including satellite-based radar interferometry and ground-based GPS measurements. In some cases, the ground may rise by several metres before an eruption.

Changes in hydrothermal activity can also suggest an imminent eruption. Many volcanoes have hot springs, geysers, or other hydrothermal features, and changes in these features can indicate changes in the underlying volcanic system. For instance, an increase in the temperature or flow rate of a hot spring could suggest that new magma is heating the groundwater.

In addition to these physical signs, changes in the behaviour of local wildlife can sometimes provide an early warning of an eruption. Some animals seem to be able to sense the subtle changes in the environment that precede an eruption, and their unusual behaviour can serve as a warning sign.

However, it's important to note that these indicators are not foolproof. Not all volcanoes exhibit all of these signs before an eruption, and sometimes these signs can occur without an eruption following. Therefore, predicting volcanic eruptions remains a challenging task, and ongoing research is aimed at improving our understanding of these complex natural systems.