An underwater volcano off Tonga erupted on Jan. 15, triggering tsunami warnings and evacuation orders in Japan and causing large waves in several South Pacific islands, where footage on social media showed waves crashing into coastal homes.
Hunga Tonga-Hunga Ha’apai lies about 65 km (40 miles) north of Nuku’alofa, the capital of Tonga. Scientists said the volcano – which last erupted in 2014 – had been puffing away for about a month before rising magma, superheated to around 1,000 degrees Celsius (1,832 Fahrenheit), met with 20 degree (68 Fahrenheit) seawater on Saturday, causing an instantaneous and massive explosion.
Under the Pacific
The island archipelago of Tonga lies on the Pacific Ring of Fire, a region known for volcanic eruptions and regular earthquakes. The area forms a horseshoe bend that stretches from New Zealand to the Philippines, Indonesia and Chinese coasts, extending to the western coasts of North and South America until the tip of Chile.
Tonga sits at the junction of two major tectonic plates, the Pacific Plate and Indo-Australian Plate. The Pacific Plate is pushed west and sinks back into the mantle along a “subduction zone” as it reaches the Indo-Australian plate and the smaller Tonga Plate. Magma is formed above the subducting plate and slowly rises through the crust above, forming a chain of volcanoes nearby.
Area of detail
Islands above
water level
Australia
N. Zealand
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volcanoes
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Niuafo'ou
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Hunga Tonga
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50 km
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Pacific Ocean
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Australia
New Zealand
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water level
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Niuafo'ou
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Pacific plate pushed under the Tonga plate. Magma rises to form a volcanic arc.
Tonga
Trench
INDO-
AUSTRALIAN
PLATE
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volcanoes
TONGA
Hunga-Tonga-
Hunga-Ha'apai
volcano
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PLATE
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Pacific Ocean
Area of DetaiL
Australia
New Zealand
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water level
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volcanoes
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Pacific plate pushed under the Tonga plate. Melting creates magma which rises to form a volcanic arc.
Tonga
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NIUE
INDO-AUSTRALIAN
PLATE
String of
volcanoes
TONGA
Hunga-Tonga-
Hunga-Ha'apai
volcano
50 km
Pacific Ocean
Area of DetaiL
Australia
New Zealand
Ocean floor
Islands above
water level
Active
volcanoes
SAMOA
PACIFIC
PLATE
Niuafo'ou
PLATE
TONGA
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Subduction
Pacific plate pushed under the Tonga plate. Melting creates magma which rises to form a volcanic arc.
FIJI
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NIUE
String of
volcanoes
INDO-AUSTRALIAN
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Hunga-Tonga-
Hunga-Ha'apai
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50 km
“We believe the base of the volcanic edifice failed and collapsed into a shallow magma reservoir, allowing the Pacific ocean waters (perhaps 100m deep) to explosively interact with the liquid rock, causing a partial caldera collapse and explosive eruption,” said James Garvin, chief scientist at NASA’s Goddard Space Flight Center.
Garvin and a team of researchers from NASA, Columbia University, Tonga and Canada have been mapping the area, above and below the water line since 2015. They have used a combination of satellite data and land-based surveys as well as sonar-based bathymetry data collected by the Schmidt Ocean Institute, in partnership with NASA and Columbia University.
Above the surface of the water, a volcanic island built by previous eruptions is the only visible sign of the volcano. This model shows the shape of the land in 2015, after an eruption joined two smaller islands into one landmass around 3 km long.
Hidden below the water is a large underwater volcano that rises 1.8 km from the seabed and stretches 20 km across. The large caldera is submerged and measures 5 km in diameter.
“Studying this eruption cycle thanks to 21st century datasets from space, ship, drones and field studies will advance understanding and ultimately predictions of how such hydrovolcanic eruptions operate,” Garvin said.
The volcanic island has changed dramatically. Satellite images from Planet Labs on January 7 showed volcanic gas escaping through the vent. On January 15, about two hours before it erupted, images show the vent was predominantly underwater. The island was mostly obliterated during the recent eruptions, leaving two small land masses once again separated by the ocean.
Jan. 7
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Tsunami alert
The eruption caused a 1.2-metre (four-foot) tsunami wave, Australia’s Bureau of Meteorology said. The waves travelled as far as Japan, nearly 8,000 km north west of the archipelago. The government’s meteorological agency issued a warning that waves reached up to 3 metres in at least two locations on its eastern coast.
Two people reportedly drowned in Peru – over 10,000 km west of the eruption – in unusually high waves.
News from Tonga is sparse because communications are severely hampered. In its first statement the country’s government confirmed three casualties, including a British national who died while saving her dogs.
Waves reach
mainland Japan
11 hours after
eruption
0.06
1.74 metre
Maximum water
height
U.S.
JAPAN
MEXICO
Hawaii
Pacific Ocean
PERU
Tonga
Eruption
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1.74 meter high wave
at Chanaral, Chile
Waves reach
mainland Japan
11 hours after
eruption
0.06
1.74 metre
Maximum water
height
UNITED STATES
JAPAN
MEXICO
Hawaii
Pacific Ocean
Waves arrive at
Peru’s Callao La Punta
22 hours after eruption
PERU
Tonga
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1.74m wave
hit Chanaral, Chile
Eruption
CHILE
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High waves strike
mainland Japan 11 hours
after the eruption
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Maximum water
height
UNITED STATES
JAPAN
MEXICO
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Waves arrive at
Peru’s Callao La Punta
22 hours after eruption
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CHILE
1.74 metre high wave
at Chanaral, Chile
NEW ZEALAND
High waves strike
mainland Japan 11 hours
after the eruption
0.06
1.74 metres
CANADA
Maximum water height
UNITED STATES
JAPAN
MEXICO
Hawaii
Pacific Ocean
PERU
Waves arrive at
Peru’s Callao La Punta
22 hours after eruption
Tonga
1.74 meter high wave
at Chanaral, Chile
AUSTRALIA
Eruption
CHILE
NEW ZEALAND
The eruption was so powerful that space satellites captured not only huge clouds of ash but also an atmospheric shockwave that radiated out from the volcano at close to the speed of sound.
6.10 pm
5.10 pm local time
Satelite images: NOAA / CIRA / RAMMB
6.10 pm
5.10 pm local time
Satelite images: NOAA / CIRA / RAMMB
6.10 pm
5.10 pm local time
Satelite images: NOAA / CIRA / RAMMB
6.10 pm
5.10 pm local time
Satelite images: NOAA / CIRA / RAMMB
6.10 pm
5.10 pm local time
Satelite images: NOAA / CIRA / RAMMB
Cut off from the world
Australia and New Zealand sent surveillance flights to assess the damage in Tonga’s outer islands, where communication is completely cut off.
The eruption has also severed the Tonga Cable, a 827 km submarine fibre-optic cable that connects the island country to Fiji and international networks. The CS Reliance, a cable laying vessel owned by U.S. subsea cable repair company Subcom is expected to repair the cable. The vessel is travelling from Port Moresby, nearly 4,000 km away.
Port Moresby
Nearly 4,000 km away
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PapUa New
Guinea
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“This disaster has shaken the people of Tonga like nothing we have seen in our lifetime,” Sione Taumoefolau, secretary general of Tonga Red Cross, said in a statement. “The tsunami has wiped out homes and villages, but we are already rebuilding amid the ashes.”
Additional work by
Kanupriya Kapoor, Manas Sharma and Aditi Bhandari
Sources
Planet Labs; Telegeography; National Oceanic and Atmospheric Administration; Natural Earth; Global Volcanism Program, Smithsonian Institution; Japan Meteorological Agency; Regional and Mesoscale Meteorology Branch; Cooperative Institute for Research in the Atmosphere; General Bathymetric Chart of the Oceans; NASA Goddard Space Flight Center2016 R/V Falkor sonar bathymetry was collected by Schmidt Ocean Institute (SOI) on behalf of NASA Goddard Space Flight Center and partners from Columbia University’s Lamont Doherty Geophysical Observatory. Data analysed by NASA Goddard and Columbia University.
2015 surface elevation models were made at NASA Goddard Space Flight Center using Maxar WorldView stereo optical images.