Question: If there is no earthquake occurring, how do you know when a volcano is about to erupt?

Hello nteedo1009! That’s a great question. Besides using earthquakes or seismic activity, geologists can use ground deformation near the volcano. When magma moves up near the surface, it takes up space and pushes the surrounding rock outward. This also causes the surface of the volcano to deform.

Some geologists also monitor the gases released from volcanic vents. They are looking for drastic temperature increases as a sign of possible volcanic activity. An increase in temperature means that magma has moved much closer to the surface.

A third possible way is obtaining thermal satellite images of a volcanic area. They take these images weekly or monthly and compare them to try to find any changes in temperature.