Volcanoes - Volcano Monitoring Using Tiltmeters

Tiltmeters have long been used to study active volcanoes by monitoring their changing shape precursory to and during eruptions. When pressurized magma enters the magma chamber beneath a volcano, the ground is forced upward, causing the slopes of the volcano to tilt away from the center of uplift. Before an eruption occurs, magma flows toward the surface, deflating the magma chamber and causing a reversal in the tilt directions. This characteristic behavior, coupled with measurements of earthquake frequency and magnitude, is used successfully by volcanologists around the world to predict eruptions hours to days before the actual event.