Volcano Number: 0403-04= Last Known Eruption: 2009

Summit Elevation: 149 m

Latitude: 20.57°S  20°34'0"S Longitude: 175.38°W 175°23"W

Last Known Eruption: 2009
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 and Hunga Ha'apai reach an elevation of only 149 m
and 128 m above sea level, respectively, and 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 the
most prominent historically active vent. Several submarine eruptions have occurred at Hunga Tonga-Hunga Ha'apai since
the first historical eruption in 1912.

The small islands of Hunga Tonga (upper left) and Hunga Ha'apai (left) cap a large seamount located about 30 km SSE of Falcon Island. The two linear andesitic islands are about 2 km long. They have inward-facing cliffs that represent the western and northern remnants of a the rim of a largely submarine caldera lying east and south of the islands. A rocky shoal is visible 3.2 km SE of Hunga Ha'apai and 3 km south of Hunga Tonga and marks the most prominent historically active vent. Aerial photo by Tonga Ministry of Lands, Survey, and Natural Resources, 1991 (published in Taylor and Ewart, 1997)./GVN

June 1988
Fishermen reported the beginning of an eruption E of Hunga Ha'apai Island on 1 June at 0800. They noted the ejection of
"fire," tephra, and large volumes of dense white smoke/steam. Sea water nearby was warm. The next day, there was an
active eruption at the S edge of a shoal. Vigorous steam emission was occasionally punctuated by ejection of solid material. On 3 June at 0915, the eruption was continuing in shallow water ~1 km SSE of Hunga Ha'apai. Lava had apparently been erupted from three sources in a SW-NE trend extending 100-200 m, with current activity at the SW end. There was no evidence of a new island.

March 2009
A new eruption from multiple vents on and near Hunga Ha'apai Island began producing ash and steam plumes sometime
in the late afternoon of 17 March 2009.

Closeup aerial photograph of the Hunga Ha'apai eruption at 1804 on 17 March 2009. Horizontal plumes on the ocean, tephra fallout, and discolored water can be seen. Courtesy of Steven Gates/GVN. Photograph of a steam-and-ash plume rising from Hunga Ha'apai Island and a submarine vent to the S erupting black tephra. View is looking NW on 18 March 2009. Photo from unknown photographer on the Sloban boat provided by Dana Stephenson/Getty Images on boston.com./GVN

On 19 March flights were disrupted and rerouted around the activity following warnings from Airways New Zealand and
MetService NZ. An aviation notice on 18 March based on ground observations from the Tongatapu airport of a plume
rising to an altitude of 7.6 km at 0659 that morning; ash was not seen in satellite data. Later that day, at 1330,
a plume seen on MODIS satellite imagery was within 1 km of the vent and moving NE. A similar plume was reported
based on MODIS and ground observations to an altitude of 4.5 km at 1600. Airport observers continued to report a plume
to 5 km altitude at 1000 on 19 March, and to 4 km at 1700, but with a band of ash extending 2.5 km NE from the
volcano to 2.4 km altitude.
A new eruptive episode was reported by Tongatapu airport at 1409 on 21 March that sent an ash plume 800 m high.

Aerial photo showing the vegetated islands of Hunga Ha'apai before the eruption. Courtesy of Brad Scott, GNS Science.

The eruption from Hunga Tonga-Hunga Ha'apai that began from multiple vents at Hunga Ha'apai island on 17
March 2009 ended after five days of activity on 21 March. The eruption destroyed all vegetation on the island, one of two high points on a submarine caldera rim.