Just a brief note, but today (November 13) is the 23rd anniversary of the disastrous lahar at Nevado del Ruiz in Colombia. Over 23,000 people died when a lahar, started by a relatively minor eruption of the volcano, swept down the river valleys the side of the edifice and destroyed Armero and Chinchina. The footage of rescue efforts after the lahar were devastating and heartbreaking (caution: linked video might not be for the faint of heart). Sadly, this disaster was mostly preventable as the citizens of these towns could have had at least an hour's warning to walk to higher ground, but the Colombian government did not have an effective plan in place.
My mother's home town is Pereira, to the southwest of Ruiz, and I clearly remember driving through the area hit by the lahar a few years after it occurred. It was one of those formative memories, seeing the whole area paved by the mud, rock hard by the time I saw it a few years later. However, if any good came from this event, it was that it opened many people's eyes around the world to the dangers posed by volcanoes and the relatively simple solutions to preventing tragedies like this.
Currently, there are four (yes, four) volcanoes in Colombia currently active or showing signs of activity - Galeras, Huila, Ruiz and the most recent volcano to make noise, Machin. The aforementioned Machin hasn't had an identified eruption since 1180 AD, so the increased shallow seismicity are definitely something to monitor closely.