The times and types of eruptions are shown at the top of each figure with the length of the symbol roughly proportional to the size of the eruption. Magmatic explosive eruptions are those which had a significant amount of new, juvenile magma ejected into an ash cloud.
Phreatic explosions are steam or gas explosions involving little or no magmatic material.
Dome growth eruptions are relatively quiet, non-explosive eruptions of lava onto the lava dome. This plot is for the explosive eruption period of 1980. If compared with the activity in the 1990s one must realize that the scales are very different. The number of events axis is more than a factor of two greater and the energy scale is a factor of one thousand greater. In the 1980s the sensitivity of the seismic network was much less than it is today and thus only larger earthquakes were located.