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Report on Hunga Tonga-Hunga Ha'apai (Tonga) — 21 January-27 January 2015

Hunga Tonga-Hunga Ha'apai

Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
21 January-27 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, 21 January-27 January 2015. Smithsonian Institution and US Geological Survey.

Weekly Report (21 January-27 January 2015)

Hunga Tonga-Hunga Ha'apai


20.536°S, 175.382°W; summit elev. 114 m

All times are local (unless otherwise noted)

According to a news article from 26 January, the newly-formed island at Hunga Tonga-Hunga Ha'apai was about 120 m high, 1.5 km wide (N-S), and 2 km long (W-E). The island was an estimated 1 km in diameter with a crater that was 400-500 m in diameter. It had joined Hunga Ha’apai to the W and was 150-200 m short of joining Hunga Tonga to the N. The article noted that the eruption had decreased during the previous week; there were no longer emissions rising from the vent.

Geological Summary. The small andesitic islands of Hunga Tonga and Hunga Ha'apai are part of the western and northern remnants of the rim (~6 km diameter) of a largely submarine caldera located about 30 km SSE of Falcon Island. The topmost sequence of welded and unwelded ignimbrite units from a caldera-forming eruption was 14C dated to 1040-1180 CE (Cronin et al., 2017; Brenna et al. 2022). At least two additional welded pumice-rich ignimbrite units and nonwelded pyroclastic flow deposits, below paleosols and other volcaniclastic deposits, indicated more very large previous eruptions (Cronin et al., 2017; Brenna et al. 2022). Several submarine eruptions have occurred at this caldera system since the first recorded eruption in 1912, including 1937 and S of the islands in 1988. A short eruption in 2009 added land to to Hunga Ha'apai. At that time the two islands were each about 2 km long, displaying inward-facing sea cliffs with lava and tephra layers dipping gently away from the caldera. An eruption during December 2014-January 2015 was centered between the islands, and combined them into one larger structure. Major explosive eruptions in late 2021 initially reshaped the central part of the combined island before stronger activity in mid-January 2022 removed most of the 2014-15 material; an even larger eruption the next day sent an eruption plume high into the stratosphere, triggered shock waves through the atmosphere and tsunami across the Pacific Ocean, and left only small remnants of the islands above the ocean surface.

Source: Matangi Tonga Online