Hunga Tonga–Hunga Haʻapai is a volcanic island in Tonga, located about 30 km south of the submarine volcano of Fonuafoʻou and 65 km north of Tongatapu, the country's main island. The volcano is part of the highly active Tonga-Kermadec Islands volcanic arc, a subduction zone extending from New Zealand north-northeast to Fiji.
It lies about 100 km above a very active seismic zone.
The island arc is formed at the convergent boundary where the Pacific Plate subducts under the Indo-Australian Plate.
The volcano itself is a submarine volcano that breached sea level in 2009 due to a volcanic eruption and lies underwater between two islands, Hunga Tonga and Hunga Haʻapai, which are respectively the remnants of the western and northern rim of the volcano's caldera.
The caldera is roughly 150 m below sea-level, and rises 200 m from the sea-floor. The two islands, part of the Haʻapai group, are about 1.6 km apart, and each is about 2 km long and composed largely of andesite. This andesite tends to be of the basaltic type.
Hunga Tonga reaches an elevation of 149 m, while Hunga Haʻapai comes to only 128 m above sea level. Neither island is large: Hunga Tonga is roughly 390,000 m2 and Hunga Haʻapai
is 650,000 m2 in size. Neither island is developed due to a lack of an
acceptable anchorage, although there are large guano deposits on each
island.
More information: Smithsonian Institution-Global Volcanic Program
Samples from the islands suggested a long eruptive history. One pyroclastic flow was dated to 1040-1180 CE, correlating to ash deposits found on Tongatapu, and to an unknown tropical eruption in 1108 CE that had produced 1°C of global cooling.
The caldera is believed to have been formed by this eruption. Submarine eruptions at a rocky shoal -about 3.2 km southeast of Hunga Haʻapai and 3 km south of Hunga Tonga- were reported in 1912 and 1937. Another eruption occurred from a fissure 1 km south-southeast of Hunga Haʻapai in 1988.
The islands figure in Tongan mythology as one of the few islands which were not overfished, and hence thrown down from heaven to land on earth. Tongans called them the islands which jump back and forth.
The first Europeans to see the islands were those with the Dutch explorers Willem Schouten and Jacob Le Maire in 1616. The British explorer Captain James Cook visited them several times in 1777 and learned their Tongan names.
The current extent of the island includes both the former islands of Hunga Tonga and Hunga Haʻapai. The initial 2009 eruption linked newly formed land with the larger and more westerly Hunga Haʻapai.
Hunga Tonga, in the northeast, has since become attached via a tombolo, and further sandy deposits have built up at the southern end of the connection with Hunga Haʻapai.
More information: BBC
The caldera itself has eroded rapidly in the south, originally allowing an opening of the crater to the ocean in the southeast. This has become separated from the sea by a shallow sandbar, forming a lagoon. Initially it was believed that the entire island would be eroded rapidly, but by 2017, scientists believed that the process could take decades.
On 20 December 2021 the volcano erupted again, causing a large plume that was visible from Nukuʻalofa. The Volcanic Ash Advisory Center Wellington issued an advisory to airlines. Explosions could be heard up to 170 kilometres away. The initial eruption continued until 2 am on 21 December. Activity continued, and on 25 December, satellite imagery showed that the island had increased in size.
Volcanic activity died down on 5 January before restarting on 13 January after the volcano sent an ash cloud 17 km into the atmosphere. The government subsequently issued a tsunami warning.
On 15 January, the volcano violently erupted again and was about seven times more powerful than the eruption on 20 December 2021.
There were numerous reports of loud booms across Tonga and other countries, such as Fiji and as far away as New Zealand and Australia. A boom was heard in Alaska seven hours after eruption meaning the sound wave traveled 830 mph.
Near the eruption, the explosion damaged property, including shattered windows. A tsunami warning was issued just after 5:30 p.m. by the Tonga Meteorological Services and the tsunami flooded coastal areas in Tonga. A 1.2 m tsunami was observed in Nukuʻalofa, Tonga and a 0.61 m one in American Samoa.
It was reported on 16 January that radar surveys before and after the eruption show that most of the island has been destroyed.
More info: National Environmental Satellite Data and Information Service
Whether it is a tsunami, or whether it is a hurricane,
whether it's an earthquake
-when we see these great fatal and natural acts,
men and women of every ethnic persuasion
come together and they just want to help.
Martin Luther King III
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