The active Colo volcano is situated on the island of Una-Una in the Gulf of Gorontalo (0°10'S and 121°35'E). This isolated volcano is located in a peculiar tectonic position, ca 70 km south of the extinct northern volcanic arm of Sulawesi and ca 40 km north of the volcanic extinct Togian Islands. There are two known historic eruptions: 1-2 May 1898 and 23 July 1983. During the latest eruption…