Seabed mapped for MH370 hunt

Broken Ridge "makes the European Alps look like foothills", says Dr Simon Boxall. Photo / AP

Mountainous landscape revealed in ocean depths.

Until now, scientists had better maps of the surface of Mars than of the Southern Indian Ocean floor.

Images show for the first time a dramatic underwater landscape with mountains higher than Mont Blanc and ridges deeper than the Grand Canyon - all 4570m below the surface.

The discoveries were made as part of the hunt for the missing Malaysian airliner, flight MH370, which disappeared six months ago.

Experts used pulses of sound, which are bounced off the seabed, to uncover this previously uncharted world.

The resulting 3D maps reveal mountain ranges, with some peaks more than 1.5km-high, trenches 1400m deep and what is believed to be a submarine volcano, bigger than Mt St Helens.

The maps cover an area either side of a range known as Broken Ridge, 1770km off the west coast of Perth.

It once formed the margin between two geological plates that separated between 20 and 100 million years ago.

"The terrain of the area around Broken Ridge makes the European Alps look like foothills," said Dr Simon Boxall, a lecturer in ocean and earth science at the University of Southampton. If you stood in the valley you would have, towering above you, mountains that were about 3km high - just coming straight up in front of you."

The maps were produced by the Australian Transport Safety Bureau (ATSB).

Watch:MH370: Malaysians pay tribute to passengers of missing jet

The aircraft vanished without trace on March 8 this year with 239 people on board. It was en route to Beijing from Kuala Lumpur when it disappeared. No trace of the plane has been found.

The search was narrowed in April after "pings" from the plane's satellite communication system placed it somewhere along a 4000km curve in the Southern Indian Ocean known as the "seventh arc".

Experts believe this area, which is around 60,570 sq km - roughly the size of Croatia - is where the aircraft's fuel ran out.

The next stage of the search involves going underwater. But before this could begin, the ATSB has had to produce these maps. It is working with Geoscience Australia on the bathymetric survey, which involves obtaining measurements of the depth of the ocean. The work is expected to take 12 months and so far, 41,300sq km of the search area have been analysed and mapped.

They are vital for when deep-sea search vehicles examine the seabed. The equipment is pulled along just above the sea floor by a 9.5km long armoured cable.

"What you are doing is flying a piece of equipment very close to the sea floor and if you don't know what is there in the first place, you end up driving into a mountain," said Boxall.

The underwater search is expected to start next month. While the families of the passengers on board MH370 hope the searches will provide answers, Boxall said the chances of finding MH370 were still "very slim".

"Sadly, they will have to decide where to draw the line. It will be a question of tripping over it luckily. They could still go over it and miss it, it could have sunk deep into the sediment."