A giant green cloud in the ocean near Tonga’s main island of Tongatapu could be a clue to a huge underwater eruption.
The cloud was photographed by a NASA satellite late last month and spotted by a University of Auckland scientist.
It is near where a new island has formed after an earlier eruption at the end of 2014 and beginning of 2015.
The island is 33km offshore from Tongatapu.
University of Auckland coastal geomorphologist Dr Murray Ford said he had been using NASA’s Landsat pictures to study the kilometre-wide island, which is made of ash and large rock fragments.
“It’s come out of nowhere,” Dr Ford told the New Zealand Herald.
He said the underwater plume was 30km long and 20km wide.
The plume, appearing as a greenish cloud in the ocean, was captured by the open-source US Geological Survey/NASA Landsat 8 satellite on January 27.
“It’s come out of nowhere,” said Ford, who immediately contacted volcanologists at the university.
“It was pretty unusual to get an image without any cloud in it – and then I saw this big, turbid plume of volcanic debris, so I checked in with our volcanologists to see what was going on.”
Dr Ford told Radio New Zealand the plume should be visible to mariners sailing through the area.
“Any boats passing through or fishing might notice some discolouration of the water but I’m not too sure whether it would be visible from land,” he said.
Institute of Geological and Nuclear Sciences volcanologist Brad Scott said GNS scientists were contacting colleagues in Tonga.
“We are relatively confident that these images are representing a submarine eruption,” Dr Scott said.
The plume appears to come from a site that last erupted between December 1998 and January 1999.
The main points
- A giant green cloud in the ocean near Tonga’s main island of Tongatapu could be a clue to a huge underwater eruption.
- The cloud was photographed by a NASA satellite late last month and spotted by a University of Auckland scientist.
- It is near where a new island has formed after an earlier eruption at the end of 2014 and beginning of 2015.
- The island is 33km offshore from Tongatapu.
For more information
NZ scientist discovers huge undersea eruption
Scientist discovers underwater eruption in Tonga
