No one was killed or injured in the eruption. But officials warned that the volcano could remain volatile.
Galeras, located in the Andes mountains near Colombia's border with Ecuador, erupted 10 times in 2009. Most people living in the vicinity have grown used to the alerts and refuse to evacuate when ordered to by local authorities.
Thousands of revelers celebrating the annual Black and White Carnival in the nearby city of Pasto were startled by Saturday's eruption but the festivities carried on.
A massive eruption of the Galeras volcano killed 10 people in 1993. (Reporting by Hugh Bronstein; Editing by Doina Chiacu)