Hunga Tonga
Encyclopedia
Hunga Tonga-Hunga Haapai is a volcano
located about 30 km south-southeast of Fonuafoou
(also known as Falcon Island), part of Tonga
.
The volcano is part of the highly active Tonga-Kermadec Islands
volcanic arc
, a subduction zone extending from New Zealand
north-northeast to Fiji
. The volcano lies about 100 km (62.1 mi) above a very active seismic zone. Magma
is formed as two tectonic plates melt together under high heat and pressure, and the superheated rock is forced to the surface.
The volcano itself is a submarine volcano
lying underwater between the two island
s, which are the remnants of the western and northern rim of the volcano's caldera
. The two islands (part of the Haapai group
) are about 1.6 km (0.994196378639691 mi) apart, and each is about 2 km (1.2 mi) long and composed largely of andesite
. Hunga Tonga reaches an elevation of 149 m (489 feet), while Hunga Haapai comes to only 128 m (420 feet) above sea level. Neither island is large: Hunga Tonga is roughly 39 hectares (0.15 square miles) and Hunga Haapai is 65 hectares (0.25 square miles) 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 mi) southeast of Hunga Haapai and 3 km (1.9 mi) south of Hunga Tonga were reported in 1912 and 1937. Another eruption occurred from a fissure 1 km (0.621372736649807 mi) south-southeast of Hunga Haapai 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.
On March 16, 2009, a submarine eruption near Hunga Tonga-Hunga Haapai began spewing steam, smoke, pumice
, and ash thousands of feet into the sky above the ocean. By March 21, Tonga's chief geologist, Kelepi Mafi reported, lava and ash from two vents, one on the uninhabited island Hunga Haapai and another about 100 metres (330 feet) offshore, had filled the gap between the two vents, creating new land surface that measured hundreds of square metres. The eruption devastated Hunga Haapai, covering it in black ash and stripping it of vegetation and fauna.
The volcanic eruption drew worldwide attention. The volcano was featured in a segment of the television program Angry Planet
in 2009.
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...
located about 30 km south-southeast of Fonuafoou
Geography of Tonga
-Geology:Though administratively divided into the three main island groups of Tongatapu, Ha'apai, and Vava'u , the Tonga archipelago is actually made of two geologically different parallel chains of islands....
(also known as Falcon Island), part of Tonga
Tonga
Tonga, officially the Kingdom of Tonga , is a state and an archipelago in the South Pacific Ocean, comprising 176 islands scattered over of ocean in the South Pacific...
.
The volcano is part of the highly active Tonga-Kermadec Islands
Kermadec Islands
The Kermadec Islands are a subtropical island arc in the South Pacific Ocean northeast of New Zealand's North Island, and a similar distance southwest of Tonga...
volcanic arc
Volcanic arc
A volcanic arc is a chain of volcanoes positioned in an arc shape as seen from above. Offshore volcanoes form islands, resulting in a volcanic island arc. Generally they result from the subduction of an oceanic tectonic plate under another tectonic plate, and often parallel an oceanic trench...
, a subduction zone extending from New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
north-northeast to Fiji
Fiji
Fiji , officially the Republic of Fiji , is an island nation in Melanesia in the South Pacific Ocean about northeast of New Zealand's North Island...
. The volcano lies about 100 km (62.1 mi) above a very active seismic zone. Magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
is formed as two tectonic plates melt together under high heat and pressure, and the superheated rock is forced to the surface.
Volcano and caldera
Submarine volcano
Submarine volcanoes are underwater fissures in the Earth's surface from which magma can erupt. They are estimated to account for 75% of annual magma output. The vast majority are located near areas of tectonic plate movement, known as ocean ridges...
lying underwater between the two island
Island
An island or isle is any piece of sub-continental land that is surrounded by water. Very small islands such as emergent land features on atolls can be called islets, cays or keys. An island in a river or lake may be called an eyot , or holm...
s, which are the remnants of the western and northern rim of the volcano's caldera
Caldera
A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...
. The two islands (part of the Haapai group
Ha'apai
Haapai is a group of islands, islets, reefs and shoals in the central part of the Kingdom of Tonga, with the Tongatapu group to the south and the Vavau group to the north. Seventeen of the Haapai islands are populated....
) are about 1.6 km (0.994196378639691 mi) apart, and each is about 2 km (1.2 mi) long and composed largely of andesite
Andesite
Andesite is an extrusive igneous, volcanic rock, of intermediate composition, with aphanitic to porphyritic texture. In a general sense, it is the intermediate type between basalt and dacite. The mineral assemblage is typically dominated by plagioclase plus pyroxene and/or hornblende. Magnetite,...
. Hunga Tonga reaches an elevation of 149 m (489 feet), while Hunga Haapai comes to only 128 m (420 feet) above sea level. Neither island is large: Hunga Tonga is roughly 39 hectares (0.15 square miles) and Hunga Haapai is 65 hectares (0.25 square miles) 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 mi) southeast of Hunga Haapai and 3 km (1.9 mi) south of Hunga Tonga were reported in 1912 and 1937. Another eruption occurred from a fissure 1 km (0.621372736649807 mi) south-southeast of Hunga Haapai 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
Willem Schouten
Willem Cornelisz Schouten was a Dutch navigator for the Dutch East India Company. He was the first to sail the Cape Horn route to the Pacific Ocean.- Biography :Willem Cornelisz Schouten was born in c...
and Jacob Le Maire
Jacob Le Maire
Jacob Le Maire was a Dutch mariner who circumnavigated the earth in 1615-16. The strait between Tierra del Fuego and Isla de los Estados was named the Le Maire Strait in his honor, though not without controversy...
in 1616, although the British explorer Captain James Cook
James Cook
Captain James Cook, FRS, RN was a British explorer, navigator and cartographer who ultimately rose to the rank of captain in the Royal Navy...
visited them several times in 1777 and learned their Tongan names.
2009 eruption
Pumice
Pumice is a textural term for a volcanic rock that is a solidified frothy lava typically created when super-heated, highly pressurized rock is violently ejected from a volcano. It can be formed when lava and water are mixed. This unusual formation is due to the simultaneous actions of rapid...
, and ash thousands of feet into the sky above the ocean. By March 21, Tonga's chief geologist, Kelepi Mafi reported, lava and ash from two vents, one on the uninhabited island Hunga Haapai and another about 100 metres (330 feet) offshore, had filled the gap between the two vents, creating new land surface that measured hundreds of square metres. The eruption devastated Hunga Haapai, covering it in black ash and stripping it of vegetation and fauna.
The volcanic eruption drew worldwide attention. The volcano was featured in a segment of the television program Angry Planet
Angry Planet
Angry Planet is a 39 part television series broadcast around the world featuring the adventures of storm chaser George Kourounis, Angry Planet is produced by Peter Rowe of Pinewood Films...
in 2009.
External links
- "Underwater Volcano Erupts Off Tonga." BBC News. March 19, 2009. - Video showing the March 18, 2009, eruption
- "Expedition To A New Island" - Explorer George Kourounis sets foot on a brand new volcanic island