Since the "surprise" eruption of Chaiten in southern Chile (still erupting away), I'm sure there has been a lot of talk about better monitoring and predictions for volcanic eruptions. Now, we don't know the full extent of the facts, but usually an eruption of the magnitude of Chaiten (VEI 6, i.e., BIG) don't just go off out of the blue. There are precursors, such as seismicity under the volcano, uplift of the land over the volcano (think of the bulge of Mt. Saint Helens prior to the 1980 eruption), increasing emissions of volcanic gases such as carbon dioxide or sulfur dioxide, increase in stream/spring water temperatures near the volcano, increase in the temperature of the land at the volcano. These are just some of the ways to watch volcanoes looking for signs of potential eruptions.
However, it is not financially possible to wire up every volcano in a volcanically active ...
