Report on Hunga Tonga-Hunga Ha'apai (Tonga) — 7 January-13 January 2015
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 7 January-13 January 2015
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2015. Report on Hunga Tonga-Hunga Ha'apai (Tonga). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 7 January-13 January 2015. Smithsonian Institution and US Geological Survey.
Hunga Tonga-Hunga Ha'apai
20.536°S, 175.382°W; summit elev. 114 m
All times are local (unless otherwise noted)
Based on a pilot observation, the Wellington VAAC reported that a dark ash plume from Hunga Tonga-Hunga Ha'apai rose to an altitude of 4.9 km (16,000 ft) a.s.l. on 12 January.
Geologic Background. The small islands of Hunga Tonga and Hunga Ha'apai cap a large seamount located about 30 km SSE of Falcon Island. The two linear andesitic islands are about 2 km long and represent the western and northern remnants of the rim of a largely submarine caldera lying east and south of the islands. Hunga Tonga reaches an elevation of about 114 m above sea level, and both islands display inward-facing sea cliffs with lava and tephra layers dipping gently away from the submarine caldera. A rocky shoal 3.2 km SE of Hunga Ha'apai and 3 km south of Hunga Tonga marks a historically active vent. Several submarine eruptions have occurred at Hunga Tonga-Hunga Ha'apai since the first historical eruption in 1912. An eruption that began in mid-December 2014 built a new island between the other two large islands.