Zenith Plateau as the final resting place for MH370

The underwater search for the missing Malaysia Airlines MH370 has become focused on the Zenith Plateau in the eastern Indian Ocean, lying about 1000 km to its nearest point on the Western Australia coast, or 1680 km north-west of Perth. The plateau is surrounded by the extensive Wharton Basin to the west and north, joins to the Quokka Rise and Wallaby (or Cuvier) Plateau in the east, and to the south by the Perth Abyssal Plain.

The origin of this plateau is proposed to be a fragment of continental crust that started rifting from the north-west Australian margin during the break-up of Gondwana in the Late Jurassic. The continued north-westerly migration of the India plate away from Australia resulted in extinct spreading ridges and volcanoes that blanketed the region in basaltic rocks during the Cretaceous. Subsequent drowning of the plateau in the Eocene has resulted in a thick build-up of calcareous ooze that now forms the present day seafloor.

The Zenith Plateau has a dimension of about 300 km wide in the east-west direction and about 220 km in the north-south direction. The plateau is relatively deep with its shallowest point at 1671 m and gently deepening towards the Wharton Basin in north at around 5000 m. The Wallaby-Zenith Fracture Zone forms an escarpment along the southern margin with a steep drop of between 2000 to 3000 m into a narrow trough with depths close to 6000 m. This narrow trough separates the Zenith Plateau from the adjacent Perth Abyssal Plain to the south.

The plateau is very poorly mapped with no modern multibeam surveys anywhere over this feature. Our current understanding of the bathymetry (depth) of the plateau are therefore based on older singlebeam echosounder data and coarse satellite gravity data. Within the present MH370 search zone on the northern flank of the plateau, seafloor depths range from about 3500 to 4500 m. The finer-scale seafloor topography in the search zone appears to vary by up to 300 m in height over distances of approximately15 km, but cannot be confirmed with the coarse data available.

Despite the deep depths on the plateau, the gentle sloping seafloor, (apparently) limited finer-scale topographic relief and the soft sediment nature of the seafloor, could provide a helpful background environment during the seabed search for the MH370 using the Bluefin-21 AUV's sidescan sonar and optical imagery.

Word of the day: Bathymetry