An increase in the frequency of volcanic quakes is a sign of impending volcanic eruption.

Occurrence of springs/wells around a volcano is a sign of impending volcanic eruption.

Drying up of vegetation around the volcanoes’ upper slopes is a sign of impending volcanic eruption.

Decrease of temperature of hot springs and wells near a volcano is a sign of impending volcanic eruption.

Crater glow due to presence of magma is a sign of impending volcanic eruption.