Scientists who specialise in volcanoes are called volcanologists.
They are getting better at predicting volcanoes. The most reliable method is listening to the 'rumbles' inside a grumbling mountain.
They also look at the changes in the gases which come out of volcanic mountains, the angle of the slopes, and bizarrely, the behaviour of animals in the area.
Animals often seem to be able to 'detect' when an eruption is coming, and they become agitated and worried.