Tongan geologists baffled by theory the new island eruption linked to red tides

The nearly simultaneous occurrence of red tides and powerful volcanic eruptions in Tonga since December 2014 leaves geologists in Tonga looking for answers.

A new volcanic island with an approximate size of  2 square kilometres and 100 metres in height has been created after a powerful volcanic eruption between the Hungas sent a plume of large ash high into the sky.

The ongoing eruptions of the Ha’apai volcanoes were first reported on December 20, 2014.

Yesterday Tongan authorities released photos with captions of the island forming, showing billowing smoke  steam and ash as well as rocks spewed out from a crater between Hunga Tonga and Hunga Ha’apai.

Red tides

Red tides were first reported in Neiafutahi and the outer islands of Okoa and ‘Oloʻua in Vavaʻu on December 28, 2014. Tongan geologists at the time said they noticed something similar to “oil slick” floating on top of the red tides.

The red tides had struck Tongatapu and ‘Eua Island this week with reports of dead fish washed ashore as well as strong smell being sent from the scenes.

Tonga’s Ministry of Fisheries said the red tides in Vava’u were caused by a bloom of reddish-brown algae that had been grown out of control. The Ministry’s director, Dr Vailala Matoto said the algae was microscopic and it could hardly be seen by naked eyes.

He said it was normal that this type of algae released chemical compounds that give off an ocean smell at the same time sent oxygen gas into the environment.

Changing the ocean colour into red or green, red tides could happen in summer time and sometimes because of the climate changes, Dr Matoto said.

But this week some theorists related red tides in Tongatapu and ʻEua Island to the Hungas’ volcanic activity saying the gases it released changed ocean colours into red blood sea.

While New Zealand geologists and scientists were  in Tonga to study the volcanic eruptions a statement from Tonga’s Ministry of Land & Natural Resources says they have yet to conclude if there was a connection between the red tides and the Hungas’ volcanic  activities.

“It is unclear at this stage if there is any relationship between the eruption and a red algal bloom observed in seawaters around Tonga recently,” Geologist Taniela Kula said in the statement.

New Island:

Mr. Kula said: “A new island has been built by the eruption between the existing islands of Hunga Tonga and Hunga Ha’apai, and is now joined to Hunga Ha’apai.”

He said the ash deposited close to the vents was large enough to build up the newborn island of “more than 1 km wide, 2km long and about 100 m high.”

“During our observations the volcano was erupting about every 5 minutes,” he said.

“Dense ash was being erupted to a height of about 400 m, accompanied by some large rocks.

“Higher we observed mostly steam, but with some ash. Above about 1000 m, the eruption plume was almost exclusively steam.

“As the ash is very wet, most is being deposited close to the vent, building up the new island,” Kula said.

In a Daily Mail report this week headlined – Fire in the South Pacific: Hunga Ha’apai underwater volcano erupts to turn the sea blood red and the sky grey with ash – it says “When levels of nitrogen and phosphorus rise, which can be caused by underwater eruptions such as the one off the coast of Tonga, algae can multiply, the report says.

“Typically, this causes water to turn green, but the effect also causes reds and yellows to be released.

“In particular, a bloom of dinoflagellate algae causes water to turn blood red in colour”.

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