I just wanted to pass a quick new news from Colombia: Nevado del Ruiz has been placed on yellow alert status (spanish) by the Colombian survey, INGEOMINAS. The reports (spanish) describe increased sulfur odor and sulfur dioxide emissions, increased seismicity in the edifice (tens of earthquakes) over the weekend and a plume (unclear if the plume is only steam or more). You can read the full INGEOMINAS statement here (spanish). No evacuations have been called by the government, but towns around the volcano are being placed on heightened alert. Ruiz has not had any confirmed eruptive activity since 1991, the last of the eruptive period that included the 1985 lahars that killed over 25,000 in Armero. The volcano is monitored by the observatory in Manizales (spanish), where you can see the a "capture" of the seismic trace at Ruiz but I have yet to find any webcam for Ruiz.
More details as I find them.
UPDATE 10/5/2010 (note: all the links are in spanish) - Not a lot of news on Ruiz so far today, but I did find two articles. The first is actually about Cerro Machin, a volcano near Ruiz in the Central Cordillera of Colombia. Macario Londoño Jhon Bonilla from INGEOMINAS told reports that the current elevated seismicity at Machin is "normal" and that an eruption is not expected - rather the seismicity is related to hydrothermal flow or strain. However, the Regional Emergency Committee will be holding a meeting in Cajamarca with INGEOMINAS and the Volcano Observatory of Manizales to discuss the seismicity at Machin and Ruiz - and people in the Risaralda province are already wondering what to expect if Ruiz or Machin do erupt.
Top left: Nevado del Ruiz in Colombia in an undated image.