1AVI The Tofua Volcanic Arc, Kingdom of Tonga, SW Pacific: A Review of Eruptive Activity Over the Past Decade Paul W Taylor Australian Volcanological Investigations

2AVI Tofua Volcanic Arc Lau Basin  Four, possibly five eruptions Activity During the Past Decade Probable submarine activity Jan-Feb 2007 Explosive activity Aug 2006 Submarine activity Sept 2001 Explosive activity Mar 2009 Pumice of unknown origin Oct 2002

3AVI September 2001 West of Vava’u  Previously unknown submarine centre west of Vava’u  T-phase seismic waves recorded in French Polynesia  Initial reports by local fisherman followed by ash-rich column  Island-like structure reported  Highly disturbed and silky surface of the sea  Notice to Mariners was issued.  Pumice rafts reported, reached Fiji in early-Nov 2001 and Australia in Oct 2002

4AVI September 2001 West of Vava’u Probable location of the active vent. (Bathymetry Arculus, 2003)  large submarine centre  no previous activity reported  large caldera present  active vent on N wall of caldera  numerous small cones in caldera  several cones outside

5AVI Home Reef  Previous activity 1852, 1857, 1984 and probably 1990  Initial submarine activity, island often formed  1984 eruption formed island and produced extensive pumice rafts  1990 activity not reported or observed only seen on aerial photographs

6AVI Home Reef: August 2006 Late Island Vava’u Home Reef Pumice Eruption column N 10kms 08 August August 2006  Activity first reported am 08 August on MODIS image. Glow in sky seen from Vava’u in evening  11 Aug: Pumice rafts entered by yacht N of Late  12 Aug: Explosive activity at Home Reef observed from yacht  Aug: Pumice rafts moved to NW  26 Aug: Island present on MODIS image  Late-Aug: Explosive activity ceases?  07 Dec: Island observed by NZ air force. Crater still steaming  Feb 07: Only small mound of pyroclastic material present.

7AVI Home Reef: February 2007

8AVI Home Reef 2006: The Pumice Vava’u 10kms N 11 August SW of Vava’uEarly-Dec Tanna Is Vanuatu 10 August

9AVI Hunga Tonga & Hunga Ha’apai: March 2009

10AVI Hunga Tonga & Hunga Ha’apai: March Marcham 19 March pm 19 March

11AVI Submarine Volcano III: Jan-Feb 2007  Previous eruptions 1911, ? and 1999  2007 activity may have been submarine hydrothermal  Mid-Jan: discoloured water reported by fishing boat  27 Jan: “bright green patch of water” reported in area. Patches spread over area 2 nm 2. Strong smell of sulphur downwind  5-6 Feb: series of seismic event in area. Possible submarine activity  Local Notice to Mariners was issued.

12AVI October 2002: Pumice of Unknown Origin  Between Niuafo’ou and Vava’u  Single stringers and large rafts  Moving in southerly directions  Stranding on north coast of Vava’u

13AVI October 2002 Pumice: Possible Sources No activity at any of the known centres in the region was reported

14AVI October 2002 Pumice: Probable Source  Deep submarine activity observed 2009  Explosive in character  Pyroclasts produced during activity

15AVIConclusions  4 probably 5 eruptive periods have occurred  All active centres were submarine  Some eruptions formed islands and extensive pumice rafts  Several were previously unknown vents  Bathymetry suggests many centres have had long periods of activity  Activity may be occurring continuously at some submarine centres that is not reported/observed  Considerable hazard may occur in the future