Increased seismic activity prompts Colombia to raise alert level for deadly volcano.

Colombian authorities have raised the alert level for the Nevado del Ruiz volcano to orange due to an increase in seismic activity, suggesting a greater probability of an eruption in the coming days or weeks. The Nevado del Ruiz is a stratovolcano that straddles the border between Colombia's Tolima and Caldas provinces. Colombia's biggest ever natural disaster occurred in 1985, when Nevado del Ruiz erupted, killing more than 25,000 people.