Some scientists have noticed that volcanic eruptions also go through cycles. The average eruption does not change much, however, the annual number of eruptions does. It has been demonstrated that on a decade long cycle the solar cycle and the number of volcanic eruptions do correlate with one another in some way. If the sun is more active for some reason the volcanoes here on Earth are a bit more active. No one is really sure why, but it has been demonstrated that this is the case.
Volcanic Activity does seem to undergo a cycle. The pattern of this cycle and how long there are between periods of peak activity of this cycle are of importance in any kind of general prediction. Local prediction of volcanic activity is a bit different.