Nevado del Ruiz
Nevado del Ruiz was very active in the three months before it erupted. An Italian volcanological mission analyzed gas samples from the fumaroles along the Arenas crater floor and proved them to be a mixture of carbon dioxide and sulfur dioxide, indicating a direct magmatic release into surface environment. A very high lahar risk was stressed in the mission's report delivered on October 22, 1985 and various simple preparedness techniques were proposed to local authorities.