2009 Tonga undersea volcanic eruption
Encyclopedia
Hunga Tonga
Hunga Tonga-Hunga Haapai is a volcano located about 30 km south-southeast of Fonuafoou , 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 above a very active...
, approximately 11 kilometres (6.8 mi) from the 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...
n capital of Tongatapu
Tongatapu
Tongatapu is the main island of the Kingdom of Tonga and the location of its capital Nukualofa. It is located in Tonga's southern island group, to which it gives its name, and is the country's most populous island, with approximately 71,260 residents , 70.5% of the national population...
. The volcano is in a highly active volcanic region that represents a portion of the Pacific Ring of Fire
Pacific Ring of Fire
The Pacific Ring of Fire is an area where large numbers of earthquakes and volcanic eruptions occur in the basin of the Pacific Ocean. In a horseshoe shape, it is associated with a nearly continuous series of oceanic trenches, volcanic arcs, and volcanic belts and/or plate movements...
. It is estimated that there are up to 36 undersea volcanoes clustered together in the area.
Eruption history
The initial March 16–17 eruption sent ashVolcanic ash
Volcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions, less than in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact...
and smoke
Smoke
Smoke is a collection of airborne solid and liquid particulates and gases emitted when a material undergoes combustion or pyrolysis, together with the quantity of air that is entrained or otherwise mixed into the mass. It is commonly an unwanted by-product of fires , but may also be used for pest...
up to 20 kilometres (12.4 mi) into the atmosphere
Atmosphere
An atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...
and an initial inspection reported that the volcano has breached the ocean surface. Authorities suggested at that time that the eruption did not yet pose any threat to the capital's population, and an inspection team was sent out to evaluate the volcano.
Between March 18–20, a number of Surtseyan eruption
Surtseyan eruption
A Surtseyan eruption is a type of volcanic eruption that takes place in shallow seas or lakes. It is named after the island of Surtsey off the southern coast of Iceland....
s sent ash plumes as high as 4 kilometres (2.5 mi) to 5.2 kilometres (3.2 mi) into the atmosphere, with prevailing winds pushing the ash cloud about 480 kilometres (298.3 mi) east-northeast of the eruption site and widespread and significant haze reported at Vavau 255 kilometres (158.5 mi) away. Steam plumes on March 20 were measured at 1.8 kilometres (1.1 mi) above sea level. But on March 21, an eruption sent steam and ash just 0.8 kilometre (0.497098189319845 mi) into the sky. On March 21, Tonga's chief geologist Kelepi Mafi reported lava and ash from two vents, one on the uninhabited island Hunga Haapai
Hunga Tonga
Hunga Tonga-Hunga Haapai is a volcano located about 30 km south-southeast of Fonuafoou , 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 above a very active...
and another about 100 m (328.1 ft) 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.
Latest news: 30-SEP-2009 17:47:17 -15.45 -173.38 5.2 10.0 TONGA ISLANDS Magnitude 5.2 - TONGA
Disruptions
Two Air New ZealandAir New Zealand
Air New Zealand Limited is the national airline and flag carrier of New Zealand. Based in Auckland, New Zealand, the airline operates scheduled passenger flights to 26 domestic destinations and 24 international destinations in 15 countries across Asia, Europe, North America and Oceania, and is...
airline flights into Tonga were delayed out of safety concerns caused by the volcanic ash, but flight schedules returned to normal shortly thereafter.
Tongan officials also expressed concern that the eruption could significantly harm the country's fishing industry.
Earthquake, 19 March 2009
Four days after the start of the eruption a strong earthquake2009 Tonga earthquake
The 2009 Tonga earthquake was a 7.6 magnitude earthquake that occurred off the coast of Tonga on March 19, 2009 UTC. It occurred at 18:17:41 UTC and had a depth of around . A tsunami warning was not issued in the aftermath of the earthquake, and people got angry, although this was later cancelled...
measuring 7.6 on the Richter scale also struck the region. As of yet there has been no confirmation of a direct link between the volcanic eruption and earthquake, though Ken Hudnut, a geophysicist for the United States Geological Survey
United States Geological Survey
The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The organization has four major science disciplines, concerning biology,...
, stated that "The association with the volcanic activity seems to be an interesting added dimension to this. It's not clear at this point that there is a direct association, but it seems suggestive at this point.". Keleti Mafi, the Tongan government's chief seismologist, has also suggested that the earthquake is likely to have a direct impact on the volcanic eruption, stating that the "strength of the earthquake could crack the volcano's (undersea) vent and allow more 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...
to be ejected".