Which is most likely to occur before a volcanic eruption?

An increase in earthquake activity is most likely to occur before a volcanic eruption because volcanic eruptions are often preceded by the movement of magma within the Earth’s crust. As magma rises towards the surface, it can create pressure and fracture surrounding rock. This process generates seismic activity, resulting in earthquakes. Scientists commonly use seismic monitoring to predict volcanic activity, as increased frequency and intensity of earthquakes can indicate that an eruption may be imminent.

In contrast, the other options do not typically serve as reliable indicators of an impending volcanic event. Acid rain production is generally related to atmospheric conditions and pollutants rather than volcanic processes. An increase in lava flow occurs after a volcano has erupted, as the magma escapes to the surface. Similarly, mud flows, often associated with volcanic activity, happen during or after an eruption when water combines with volcanic ash and debris, rather than before the eruption itself.