One thing that scientist use to predict volcanic eruptions is a Tiltmeter. Scientists use tiltmeters to detect increasing rates of deformation in a mountain before an eruption. What a tiltmeter does is measure the tilt or slop of the entire mountain. This provides additional information about the volcano and the magma inside it. Another thing that scientists will use is a seismometer. A seismometer is used to try and pinpoint an earthquake, which also tracks the rise of magma and its movement along fissures. There are also quite a few signs of a volcanic eruption that a scientist can use to tell if there is going to be an eruption. Some of the signs are, sulfurous odors, steam puffs coming out from cracks, restless and fleeing animals, dimming of the sun in mid-day, earth tremors, and changes in weather. These are things that almost anyone could notice. One last big thing that can help predict when a volcanic eruption is going to occur is a correlation spectrometer. A spectrometer can measure the amounts of sulfur dioxide that the volcano is letting out. Sulfur dioxide is a telltale gas that is released in increasing amounts before an eruption.
So in conclusion there are a few ways to predict volcanoes but in the end it is hard to actually tell when every volcanic eruption is going to occur. Volcanoes are very interesting things and really have no particular pattern to when they will erupt.
3. Gregory vogt, predicting volcanic eruptions