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Deepsea mountain mapped by RSV Nuyina

The summit of an underwater mountain, higher than Mount Kosciuszko, has been mapped for the first time by RSV Nuyina.

At 2,500 metres high, 2,900 metres wide and 4,500 metres long, the seamount had been identified from satellites at about 50 degrees South, on the edge of the ‘Furious Fifties’.

While an earlier voyage had skimmed one side of the seamount, no detailed mapping at its summit had ever been done.

Seamounts are usually formed from extinct volcanos and can be biological hotspots, attracting plankton, corals, fish and marine mammals.

As Nuyina’s passage to Davis research station took the ship directly over the seamount, the on board acoustics team took the opportunity to switch on the ship’s hull-mounted multibeam echosounder, to find out what lay beneath.

Senior Acoustics Officer, Floyd Howard, said the echosounder ‘sees’ seafloor features by emitting pings of sound in a fan-like pattern beneath the ship.

When the sound hits an object or the seafloor, it bounces back towards the ship, allowing scientists to build a picture of the seafloor – similar to echolocation used by dolphins.

As the ship cruised at 8 knots over the seamount, its surface structure and height were gradually revealed, ping by colourful ping, with different colours representing different depths.

The excitement was palpable as people gathered to see just how high the mountain would rise from a base elevation of about 3,000 metres.

“The highest point we reached was about 500 metres below the ocean surface, so it’s a significant feature,” Mr Howard said.

The team has informally named the feature ‘Ridgy-Didge Seamount’ until an official name can be bestowed upon it.

The information collected during the seamount pass, and future mapping efforts by Nuyina and other ships, will contribute to global efforts to map the world’s oceans by 2030.

Coloured map of seafloor
The seamount identified by satellites and partially mapped by RSV Nuyina Photo: Pete Harmsen/AAD
This content was last updated 2 years ago on .

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