Biggest Volcanic Eruption Seen From Space: Red Volcanic Sunset Ahead

Hunga Tonga–Hunga Haʻapai is a volcanic island[2] in Tonga, located about 30 km (19 mi) south of the submarine volcano of Fonuafoʻou and 65 km (40 mi) 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 (62 mi) 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 the two islands (Hunga Tonga and Hunga Ha'apai), which are the remnants of the western and northern rim of the volcano's caldera. The two islands (part of the Haʻapai group) are about 1.6 km (0.99 mi) apart, and each is about 2 km (1.2 mi) long and composed largely of andesite. This andesite tends to be of the basaltic type. Hunga Tonga reaches an elevation of 149 m (489 ft), while Hunga Haʻapai comes to only 128 m (420 ft) above sea level. Neither island is large: Hunga Tonga is roughly 390,000 m2 (0.15 sq mi) and Hunga Haʻapai is 650,000 m2 (0.25 sq mi) in size. Neither island is developed due to a lack of an acceptable anchorage, although there are large guano deposits on each island.

Submarine eruptions at a rocky shoal – about 3.2 km (2.0 mi) southeast of Hunga Haʻapai and 3 km (1.9 mi) south of Hunga Tonga – were reported in 1912 and 1937. Another eruption occurred from a fissure 1 km (0.62 mi) 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" (i.e. suffer earthquakes). The first Europeans to see the islands were those with the Dutch explorers Willem Schouten and Jacob Le Maire in 1616, although the British explorer Captain James Cook visited them several times in 1777 and learned their Tongan names.