Sounds of the deep: why the Mariana Trench is noisier than you think

Deployment of deep-ocean hydrophone mooring from deck of  USCG Cutter Sequoia at Mariana Trench Deployment of deep-ocean hydrophone mooring from deck of USCG Cutter Sequoia at Mariana Trench
08 Jun
2016
An ambitious scientific mission has discovered that the deepest known point in the ocean turns out to be a far noisier place than might be expected

If Mount Everest was rotated upside down and pointed into the Mariana Trench, the summit would still be a mile away from the deepest point of this underwater canyon. At 2,550km long and up to a record 11km deep at the iconic ‘Challenger Deep’, the Mariana Trench, located roughly 200km east of the Mariana Islands, is one of the furthest points on Earth away from civilisation.

You might, think, therefore, that it would be a relatively quiet place, and certainly that is what marine scientists from the National Oceanic and Atmospheric Administration (NOAA) at Oregon State University expected to find. ‘Yet there really is almost constant noise from both natural and man-made sources,’ explains Robert Dziak, a NOAA research oceanographer and chief scientist on a project to drop a titanium-encased hydrophone into the trench, which he describes as akin to ‘sending a deep-space probe to the outer solar system’.

‘We had never put a hydrophone deeper than a mile or so below the surface, so putting an instrument down some seven miles into the ocean was daunting,’ says Haru Matsumoto, an Oregon State ocean engineer tasked with creating a listening device capable of withstanding 36,000 feet-worth of oceanic pressure bearing down on it. That’s roughly 16,000 pounds per square inch (PSI), or more then 1,000 times more than regular atmospheric pressure. ‘We had to drop the mooring down through the water column at no more than about five metres per second,’ continues Matsumoto. ‘Structures don’t like rapid change and we were afraid we would crack the ceramic housing outside the hydrophone.’

110305 web3D perspective of bathymetry at Challenger Deep, Mariana Trench (Image: Center for Coastal and Ocean Mapping - Joint Hydrographic Center)

The purpose of the project was to establish a baseline for ambient sound in the ocean, in order to allow for future monitoring of sounds from maritime human activity. However, what they found was considerably more noise in the trench than was anticipated. ‘The ambient sound field at Challenger Deep is dominated by the sound of earthquakes, both near and far,’ reveals Dziak, ‘as well as the distinct moans of baleen whales and the overwhelming clamour of a category 4 typhoon that just happened to pass overhead. There was also a lot of noise from ship traffic, identifiable by the clear sound pattern the ship propellers make when they pass by.’

The range and magnitude of sounds recorded during the 23 days when the hydrophone was recording in the trench emphasises the strength which sound waves maintain over long distances underwater, with the hydrophone even picking up the sounds of waves seven miles above. ‘We recorded a loud magnitude 5.0 earthquake that took place at a depth of about 10km, or more than six miles, in the nearby ocean crust,’ says Dziak. ‘Since our hydrophone was at 11km, it was actually below the earthquake, which is really an unusual experience.’

There have famously only been two manned descents to the bottom of the trench – oceanographers Don Walsh and Jacques Piccard in 1960, and film director James Cameron in 2012 – however recent research projects such as this by the NOAA are opening the ocean up for new exploration. A follow-up mission aims to return the hydrophone – accompanied by a deep-sea camera – to the Mariana Trench next year.

Share this story...

Submit to FacebookSubmit to Google PlusSubmit to Twitter

Related items

1 comment

  • Rubeena Panwaar As still as the sea!!! But after this new discovery by hydrophone it seems that old idiom is about to change now... As noisy as the sea.... It's really surprising to know that the deepest point on the earth has a great hustle bustle than above the surface.... Saturday, 18 June 2016 08:28 posted by Rubeena Panwaar

Leave a comment

ONLY registered members can leave comments and each comment is held pending authorisation before publishing. Please login or register to voice your opinion.

Geographical Week

Get the best of Geographical delivered straight to your inbox every Friday.

Subscribe Today

EDUCATION PARTNERS

Aberystwyth UniversityUniversity of GreenwichThe University of Winchester

TRAVEL PARTNERS

Ponant

Silversea

Travel the Unknown

DOSSIERS

Like longer reads? Try our in-depth dossiers that provide a comprehensive view of each topic

  • REDD+ or Dead?
    The UN-backed REDD+ (Reducing Emissions from Deforestation and Forest Degradation) scheme, under which developing nations would be paid not to cut dow...
    The true cost of meat
    As one of the world’s biggest methane emitters, the meat industry has a lot more to concern itself with than merely dietary issues ...
    Long live the King
    It is barely half a century since the Born Free story caused the world to re-evaluate humanity’s relationship with lions. A few brief decades later,...
    London: a walk in the park
    In the 2016 London Mayoral election, the city’s natural environment was high on the agenda. Geographical asks: does the capital has a green future, ...
    The Money Trail
    Remittance payments are a fundamental, yet often overlooked, part of the global economy. But the impact on nations receiving the money isn’t just a ...

MORE DOSSIERS

NEVER MISS A STORY - follow Geographical

Want to stay up to date with breaking Geographical stories? Join the thousands following us on Twitter, Facebook and Instagram and stay informed about the world.

More articles in NATURE...

Wildlife

Aaron Gekoski continues working alongside the Wildlife Rescue Unit

Geophoto

Today, the camera is regarded as an essential smartphone feature.…

Oceans

An innovative new theory hopes to save millions of lives…

Wildlife

Aaron Gekoski continues his personal adventure into the wilds of…

Wildlife

Simple tracking devices have enabled conservationists to amass big data,…

Climate

In a new report, researchers have calculated the global emissions…

Climate

Geographical’s regular look at the world of climate change. This…

Wildlife

The latest episode sees ‘Bertie’ enlisting in wildlife rescue boot…

Energy

Icelandic engineers are attempting to harness the powerful geothermal energy…

Wildlife

New video series tracks the journey of Aaron Gekoski as…

Energy

Newly-developed ‘sustainable rubber’, produced using recycled food waste, could one…

Geophoto

This winter has seen frequent storms and flooding hitting many…

Wildlife

The bison, Poland’s symbol of nature conservation, already faces controversial…

Wildlife

Wolves have arrived at a wildlife park in Devon as…

Climate

An unassuming beach in Denmark is absorbing record-breaking levels of…

Energy

The environmental cost of military activities is significant. Could new…

Wildlife

Latest figures suggest that there are more than twice as…

Tectonics

How does the proposed allocation of ‘Zealandia’ as an independent…

Wildlife

Is extinction forever? While most would assume that yes, extinction…

Geophoto

Wide-angle photography is perhaps the best way to recreate the…