On January 31 University of Auckland geographers noted a volcanic plume on satellite images in the Tonga area. The images show a submarine volcanic eruption is now under way about 46 km north west of Nuku’alofa. Back tracking through images we can trace activity back to 23 January from this volcano. This volcano has been called ‘Submarine Volcano III’ in historic reports.

Submarine volcanic activity has been noted from this area in 1911; 1923 (steam plumes); 1970 (discoloured water); 1989-1999 (small island formed in January 1999) and 2007 (discoloured water and felt earthquakes). The 1999 activity is the best reported, starting with felt earthquakes in late December 1989 and discoloured water was noted on 7 January 1999 and an eruption column on the 8th. A volcanic cone was reported above sea level on January 12 and again in the 14th.

Satellite images obtained from the NASA Earth Science program allow us to back track the submarine activity. We can see activity in images from 23, 26, 28 and 29 January indicating the eruption has been ongoing for over a week. After contacting our colleagues in Tonga it appears a steam plume may also be present, but the local cloud makes this difficult to ascertain. Submarine eruptions can be a hazard to shipping.

Submarine volcanic activity is common in the Tonga area and some produce small islands that last for a few days to months. Examples of this include Curacoa Reef (1973), Home Reef (1984), Metis Shoal (1967-68, 1979, 1995) Falcon Island (1927-36)