History of 2009 Tonga undersea volcanic eruption
The 2009 Tonga undersea volcanic eruption began on March 16, 2009, near the island of Hunga Tonga, approximately 11 kilometers (6.8 mi) from the Tongan capital of Tongatapu. The volcano is in a highly active volcanic region that represents a portion of the Pacific Ring of Fire. It is estimated that there are up to 36 undersea volcanoes clustered together in the area.
The initial March 16–17 eruption created an ejecta column (tephra) which sent ash and smoke up to 20 kilometers (12 mi) into the atmosphere and an initial inspection reported that the volcano had 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 eruptions sent ash plumes as high as 4 kilometers (2.5 mi) to 5.2 kilometers (3.2 mi) into the atmosphere, with prevailing winds pushing the ash cloud about 480 kilometers (300 mi) east-northeast of the eruption site and widespread and significant haze reported at Vavaʻu 255 kilometers (158 mi) away. Steam plumes on March 20 were measured at 1.8 kilometers (1.1 mi) above sea level. But on March 21, an eruption sent steam and ash just 0.8 kilometers (0.50 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 Haʻapai and another about 100 m (330 ft) offshore, had filled the gap between the two vents, creating new land surface that measured hundreds of square meters. The eruption devastated Hunga Haʻapai, covering it in black ash and stripping it of vegetation and fauna.
An undersea or submarine volcano is located below the ocean surface and mostly erupts under water.
There are an estimated one million undersea volcanoes that, like continental volcanoes, are located near the Earth’s tectonic plates and where they form. These volcanoes not only deposit lava, but can also spew out large amounts of volcanic ash.
According to the Global Foundation for Ocean Exploration group, about “three-quarters of all volcanic activity on Earth actually occurs underwater”.
Undersea volcanic activities give rise to seamounts – underwater mountains that are formed on the ocean floor but do not reach the water surface.
How often does Hunga-Tonga-Hunga-Ha’apai erupt?
The Hunga-Tonga-Hunga-Ha’apai volcano, which lies about 65km (40 miles) north of the capital of Nuku’alofa, has a history of volatility.
In recent years, the Hunga-Tonga-Hunga-Ha’apai breached sea level during a 2009 eruption. In a 2015 eruption, it spewed so many large rocks and ash into the air, it caused a new island to be formed measuring 2km (1.2 miles) long and 1km wide and 100 metres (328 feet) high.
On December 20 last year and then on January 13, the volcano erupted again, creating visible ash clouds that could be seen from the Tonga island Tongatapu. On January 15, another massive eruption occurred, triggering tsunami waves.
Volcanologist and science journalist Robin George Andrews told Al Jazeera that undersea volcanoes like Hunga-Tonga-Hunga-Ha’apai erupt in such an explosive way about once every 1,000 years.
“There was this giant explosion, which scientists think is one in 1,000-year event for this sort of volcano,” he said.
“It takes about 1,000 years to fully recharge and we just happen to be around the point where is unleashed that the vast amount of its magma in a very explosive way,” Andrews said.
Effect of Tongan Volcanic Eruption on 15th January 2022
A tsunami has hit Tonga's largest island, Tongatapu, and reportedly sent waves flooding into the capital after an underwater volcano in the South Pacific exploded in a violent eruption on Saturday, sending a cloud of ash and gas steam into the air.
A tsunami warning has been issued for the islands of Tonga and parts of Japan. Tsunami advisories have also been issued for New Zealand's North Island and the west coast of the United States from California to Alaska, as well as Canada's British Columbia.
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Satellite imagery shows a massive ash cloud and shockwaves spreading from the eruption.
Waves crossed the shoreline of Tonga's capital, Nuku'alofa, on Saturday, flowing onto coastal roads and flooding properties, according to CNN affiliate Radio New Zealand (RNZ).
Tonga's King Tupou VI was evacuated from the Royal Palace after the tsunami flooded the capital, RNZ reported, citing local media reports that a convoy of police and troops rushed the monarch to a villa at Mata Ki Eua.
Residents headed for higher ground, RNZ said, as waves swept the palace grounds, waterfront and main street.
Ash was falling from the sky in Nuku'alofa on Saturday evening and phone connections were down, RNZ said.
The Hunga-Tonga-Hunga-Ha'apai volcano first erupted Friday, sending a plume of ash 20 kilometers (12.4 miles) into the air, according to RNZ.
The volcano is located about 30 kilometers (18.6 miles) southeast of Tonga's Fonuafo'ou island, according to RNZ, and about 65 kilometers (40 miles) north of Nuku'alofa.
In addition to the tsunami warning, Tonga's Meteorological Services issued advisories for heavy rain, flash flooding and strong winds in lands and coastal waters.
The nearby island of Fiji also issued a public advisory asking people living in low lying coastal areas to "move to safety in anticipation of the strong currents and dangerous waves."
Tsunami alert in effect for Fiji group
the National Disaster Management Office (NDMO) issued a public advisory for those in low-lying coastal areas to evacuate to higher grounds, with anticipation of strong currents and dangerous waves – following a series of underwater volcanic eruptions in Tonga earlier this evening.
The Fijian Government also offered prayers for the people of Tonga. “We are praying for our Tongan sisters and brothers who are beset by tsunami waves and airborne ash stemming from the eruption,” Mr Sayed-Khaiyum said at a press conference.
As a matter of precaution the people were advised to, please cover all household water tanks and stay indoors in the event of rain due to the risk of rainfall becoming acidic.”