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Video: Tonga volcano: Scientists search for cause of massive eruption
私たちは、何年もの間、日本のエンターテインメント ニュースを生き、呼吸してきた情熱的なエンターテインメント ニュース ジャンキーの小さなチームです。
tonga volcano, 2022-01-22, Tonga volcano: Scientists search for cause of massive eruption, More international aid has arrived in Tonga after an undersea volcanic eruption hit the pacific island.
The people of Tonga are now in recovery mode, trying to clean up some of the catastrophic damage left behind. There is also other work underway to understand why the massive eruption happened.
As Mike Armstrong reports, scientists have been watching this volcano for years and some are hoping their data will lead to answers.
For more info, please go to https://globalnews.ca/news/8526660/tonga-photos-damage-volcano-tsunami/
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Footage of the Hunga Tonga–Hunga Haʻapai eruption on 30 December 2021
After staying relatively inactive since 2014, the Hunga Tonga–Hunga Haʻapai volcano erupted on 20 December 2021, sending particulates into the stratosphere. A large plume of ash was visible from Nukuʻalofa, the capital city of Tonga, about 70 km (43 mi) from the volcano. The Volcanic Ash Advisory Center (VAAC) in Wellington, New Zealand, issued an advisory notice to airlines. This initial eruption ended at 02:00 on 21 December 2021.
During 22–23 December 2021, 8-to-14-kilometre-high (5.0 to 8.7 mi) plumes containing sulfur dioxide drifted to the north-northeast and spread over the Niuatoputapu, Haʻapai and Vavaʻu island groups. Surtseyan explosions, steam plumes and steam bursts were recorded by a Tonga Navy crew on 23 December 2021, during which time the first ground-based images of the eruption were created.
During 24–27 December 2021, steam and gas emissions reached altitudes of 10.3–12.2 kilometres (6.4–7.6 mi). Ash plumes reached heights of only 3 kilometres (1.9 mi), depositing ash only adjacent to the volcano. On 25 December 2021, satellite imagery revealed that the island had increased in size by 300–600 metres (980–1,970 ft) on its eastern side. During 29–30 December 2021, several surges of Surtseyan activity occurred, some of which were witnessed by passengers on a small South Seas Charters boat. Eruption plumes during the second half of December 2021 interrupted air travel to Tonga multiple times.
As activity on the island decreased, it was declared dormant by the Tonga Geological Services on 11 January 2022. A large eruption commenced on 14 January 2022 at 04:20 local time, sending clouds of ash 20 km (12 mi) into the atmosphere. The government of Tonga issued a tsunami warning to residents, and waves of 30 cm (12 in) were observed in Nuku’alofa. Later in the afternoon, Tongan geologists near the volcano observed explosions and a 5 km (3.1 mi)-wide ash column between 17:00 and 18:30 local time. A much larger Plinian eruption started the following day (15 January 2022) at 17:14 local time (04:14:45 UTC, 15 January). The eruption column from this eruption rose 58 km (36 mi) into the mesosphere. The VAAC again issued an advisory notice to airlines. Ash from the eruption made landfall on the main island of Tongatapu, blotting out the sun. Loud explosions were heard 65 km (40 mi) away in Nukuʻalofa, and small stones and ash rained down from the sky. Many residents in Tonga were stuck in traffic whilst attempting to flee to higher ground.
A four-hour observation of the January 2022 eruption over the southern Pacific Ocean from the GOES-West satellite
Shockwave from the Hunga Tonga eruption captured by GOES-17 (GOES-West) and shown using the Mid-level Water Vapor
The explosion was heard in Samoa, roughly 840 km (520 mi) away before the sound travelled to more distant countries. Residents in Fiji, more than 700 km (430 mi) away, described the sounds of thunder, while the “thump” of the eruption was also reported in Niue and Vanuatu. Tremors and shaking buildings were reported by residents in southwestern Niue, around Alofi and Avatele. The United States Geological Survey (USGS) estimated the eruption at a surface-wave magnitude of 5.8.[nb 2] The eruption was heard more than 2,000 km (1,200 mi) away in New Zealand, where the sound arrived two hours later. A series of bangs were heard around 3:30 a.m. local time in and around Anchorage, Alaska, approximately 9,700 km (6,000 mi) away from the volcano, lasting about 30 minutes. Low-frequency noise persisted for approximately two hours. Booms were heard as far away as Yukon in Canada.
An aerial capture from an aircraft viewing from the eruption on 14 January 2022
The volcanic explosion caused atmospheric shockwaves to propagate around the globe. Satellites visually captured shockwaves propagating across the Pacific Ocean and a very wide eruption column. The pressure wave was measured by weather stations in many locations, including New Zealand to a maximum amplitude of about 7 hPa, and Australia to 6.9 hPa at Lord Howe Island and 3.3 hPa at Perth. Even in Europe, a pressure fluctuation of 2.5 hPa was measured in Switzerland, and of just over 2 hPa when it reached the United Kingdom. Shockwaves were reported as having gone around the earth as many as four times in Japan and Utah, and at least twice at the Blue Hill Meteorological Observatory in Massachusetts. The pressure shockwave was also observed in Chennai, India, which is 12,000 km from the eruption site.
Intense lightning activity was recorded during the eruption phase. The Vaisala Global Lightning Dataset GLD360 detected lightning in the form of radio waves. Several hundred to a thousand flashes of lightning were recorded by the system during the two weeks before the eruption. From 14 to 15 January 2022, tens of thousands of lightning flashes occurred. Between 05:00 and 06:00 UTC on 15 January 2022, 200,000 flashes were recorded.
Preliminary observations showed that the eruption column ejected a large amount of volcanic material into the stratosphere, leading to speculation that it would cause a temporary climate cooling effect. Later calculations showed it injected an estimated 400,000 tonnes of sulfur dioxide into the stratosphere and was unlikely to have any global cooling effect. Despite this, the eruption can have a cooling effect in the Southern Hemisphere, causing slight cooling of winters and spectacular sunsets. People living in the Southern Hemisphere can expect purple sunsets for a few months after the eruption. A cooling effect of 0.1–0.5 °C (0.18–0.90 °F) may last until spring (September–November) 2022. The eruption was described as a once-in-a-thousand-year event for the Hunga caldera.
NASA satellite Aura detected the eruption using its microwave limb sounder. It measures ozone, water vapor, and other atmospheric gases, and can penetrate obstacles such as ash clouds. The undersea eruption also ejected 146 million tons of South Pacific Ocean water into the stratosphere. The amount of water vapor ejected was 10 percent of the stratosphere’s typical stock. It was enough to temporarily warm the surface of Earth. It is estimated that an excess of water vapour should remain for 5–10 years.
According to a March 2022 paper in the journal Earthquake Research Advances, Hunga Tonga–Hunga Haʻapai’s plume reached a peak height of 58 kilometres (36 mi) into the atmosphere and sustained heights greater than 30 kilometres (19 mi). The initial explosive event was possibly more powerful than the Hatepe eruption, even though Hatepe ejected over ten times the volume of material in a longer eruption. Hunga Tonga–Hunga Haʻapai erupted over a span of 12 hours, releasing 1.9 km3 (0.46 cu mi) of ejecta with an estimated mass of 2,900 teragram.
The ERA paper says the eruption correlated to a VEI of 5–6. An April 2022 research paper led by Poli and Shapiro and published by the American Geophysical Union indicates that the eruption is the largest ever observed with modern instrumentation and estimates its VEI to be approximately 6. Meanwhile, Vergoz and others estimate the blast yield to be 100–200 megatons of TNT and place the corresponding VEI at 5.8. Likewise, a study by Diaz and Rigby estimates the energetic output of the eruption to be equivalent to 61 Megatons of TNT, making the event more powerful than the largest nuclear bomb ever detonated (Tsar Bomba). The Smithsonian Institution Global Volcanism Program rated the eruption at VEI-5.
The ERA paper also concludes that this eruption resulted in the formation of a new caldera. In May 2022, scientists at the National Institute of Water and Atmospheric Research (NIWA) released a bathymetry map indicating a large caldera measuring 4 km (2.5 mi) in width formed from the eruption. Surveys also indicated that the caldera floor is located 850 m (2,790 ft) below sea level. According to a volcanologist, the caldera walls continue to experience ongoing collapses. Surveys of the seafloor around the volcano found large sediment piles, layers of fine mud and ash, and valleys up to 50 km (31 mi) from the volcano. The survey indicated that an estimated 6–7 km3 (1.4–1.7 cu mi) of debris was added to a 22,000 km2 (8,500 sq mi) area seafloor. Scientists also suggest that the volcano may still be erupting underwater.
A 2022 study in the journal Ocean Engineering by Heidarzadeh and others determined the size of the initial tsunami caused by the eruption. The study analyzed data from 22 tide gauges, eight Deep-ocean Assessment and Reporting of Tsunamis (DART) stations, eight atmospheric pressure time series, spectral analysis and computer simulation. It was concluded that the eruption displaced 6.60 × 109 m3 of seawater, 90 m (300 ft) in amplitude, with a length of 12 km (7.5 mi).
Hunga Tonga-Hunga Haʻapai in December 2021
Hunga Tonga-Hunga Haʻapai in February 2022, after the eruption
The eruption of the Hunga-Tonga-Hunga-Ha’apai volcano on 15 January 2022 was the largest recorded since the
eruption of Krakatoa in 1883. The eruption triggered tsunami waves of up to 15m which struck the west coast of
Tongatapu, ‘Eua and Ha’apai. Ashfall covered an area of at least five square kilometres.
Damage to the international and domestic undersea telecommunications meant little information was available
from Tonga following the eruption. However, New Zealand Defence Force and Australian Defence Forces
surveillance flights on 17 January showed significant damage to houses, roads, water tanks and other infrastructure
on the west coast of Tongatapu, the Ha’apai island group and the west coast of ‘Eua. On 18 January, the Prime
Minister of Tonga declared a state of emergency effective from 16 January. The Tongan Government and TRCS
requested international assistance.
Only three direct and one indirect fatality have been officially attributed to the volcano and tsunami. Early
government estimates were that 84,176 people (84 per cent of the population) on Tongatapu, Ha’apai and ‘Eua) were
affected, particularly by ashfall. Around 3,000 people were displaced in the immediate aftermath, including some
evacuated from seriously affected islands off the coast of Tongatapu and in the Ha’apai island group. Most
subsequently returned to their communities, although some families evacuated from badly affected islands remain
on Tongatapu. (IFRC, 2 Aug 2022)
Appeals and Response Plans
Maps and Infographics
- New Zealand Defense Force Tonga Response
New Zealand, which straddles the boundary between the Pacific and Australian tectonic plates and experiences significant volcanism and earthquakes, increased the alert level on Tuesday for a volcano located below the country’s biggest lake.
In a statement, the country’s geological agency GeoNet said that it had detected almost 700 small earthquakes below Lake Taupo, the caldera created by the giant volcano, and had raised the volcanic alert level to 1 from 0.
The volcanic alert system is based on six escalating levels of unrest, but GeoNet notes that eruptions may occur at any level, and levels may not move in sequence as activity can change rapidly.
The Volcanic Alert Level for Taupō Volcano has been raised to Volcanic Alert Level 1 (minor volcanic unrest). This minor unrest is causing the ongoing earthquakes & ground deformation at the volcano. Read our bulletin with all of the information here: /T9yTR3aF32 pic.twitter.com/FD31y9iYqD
— GeoNet (@geonet) September 20, 2022
GeoNet said this was the first time it had raised the Taupo Volcano alert level to one, but this was not the first time there had been unrest and said the chance of an eruption remains very low.
“The earthquakes and deformation could continue for the coming weeks or months,” the agency said.
Taupo is believed to have caused the largest volcanic eruption on Earth in the past 5,000 years when it last exploded about 1,800 years ago and spewed more than 100 cubic kilometres of material into the atmosphere.
In 2019, New Zealand’s Whakaari island volcano – also known as White Island – suddenly erupted, spewing steam and ash, killing 22 people and seriously injuring 25, mostly tourists.
Al Jazeera and news agencies
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