What do earthquakes tell us about a volcano? Earthquake activity beneath a volcano almost always increases before an eruption because magma and volcanic gas must first force their way up through shallow underground fractures and passageways. When magma and volcanic gases or fluids move, they will either cause rocks to break or cracks to vibrate. Learn more here -> https://www.iris.edu/hq/inclass/animation/volcano_monitoring_volcanic_earthquakes | EarthScope Consortium