Signs of an impending volcanic eruption, what to look for?

Monitoring Earthquake Activity

When a volcano is about to erupt, the ground beneath it typically becomes more active, with an increase in earthquakes. These earthquakes can range from small tremors to larger magnitude events. In order to track this activity, scientists use seismometers, which are instruments that measure the vibrations in the ground. A baseline of normal earthquake activity is established, and any significant increases above this baseline can indicate an impending eruption.

Ground Deformation and Gas Emissions

Ground deformation refers to the movement of the Earth’s surface, such as the swelling or sinking of the ground. This can be measured using techniques like GPS or interferometric synthetic aperture radar (InSAR). Gas emissions, including sulfur dioxide, hydrogen chloride, and hydrogen sulfide, can be detected using satellite imagery or ground-based sensors. Elevated levels of these gases can indicate magma movement and increased pressure beneath the volcano.

Observing Visual Cues

Changes in the volcano’s appearance, such as the appearance of steam vents, fumaroles, or new landforms, can indicate increased volcanic activity. A change in the color of water in rivers and lakes, indicating increased levels of dissolved minerals, can also be a warning sign. In addition, loud rumbling sounds or whistling noises, which can be heard for miles, can precede a volcanic eruption.