The search for MH370 includes a bathymetric survey, providing a detailed map of the sea floor topography of the search area; and an underwater search using scanning equipment or towed submersible vehicles. The information gained in the bathymetric survey is used to build a map of the sea floor in the search area, aiding navigation during the underwater search.
The bathymetric survey was conducted from May to October 2014, collecting data over 150,000 square kilometres in the search area and producing high resolution maps of the sea floor to safely conduct the underwater search.
Survey vessels undertaking the bathymetric survey used a multibeam sonar mounted on the hull to obtain measurements and produce a map charting the water depth and hardness of the sea floor. High resolution multibeam data acquisition is time-consuming. It is a little like mowing grass, where bathymetry is mapped line by line.
In general, the world’s deep oceans have had little exploration. Previous maps of the sea floor in the search area were derived from satellites and only indicated the depth of the ocean at a coarse resolution, not showing the shape of the sea floor in enough detail for safe navigation of underwater vehicles. These coarse maps provide data at a low resolution of approximately 1500 metres (per pixel), while the recent multibeam bathymetric survey collected data at 50 to 150 metres (per pixel). This newly acquired data is some of the first high resolution data available for these areas.
Very little is known about the sea floor in the MH370 search area, as few marine surveys have taken place there. What was known, however, was that the search area encompasses the seabed on and around Broken Ridge, an extensive linear, mountainous sea floor structure that once formed the margin between two geological plates. These plates evolved and spread apart between 20 and 100 million years ago, under similar processes found today at spreading plate margins (such as the Mid-Atlantic Ridge).
The sea floor around Broken Ridge still retains many of the large geological structures typical of spreading plate margins where volcanism and tectonic movements produce volcanoes (now extinct), high rugged ridges and deep trenches.
The high resolution bathymetry data collected in the search for MH370 has revealed many finer-scale seabed features for the first time that were not visible in the previous low resolution, satellite-derived bathymetry data. It has also revealed regions of harder and softer sea floor composition (sediment versus rock). This information has been useful in identifying and discriminating certain features, but also in providing a guide on the complexity of the sea floor for the underwater search. The following 3D models present some of the features.
These three-dimensional models of the sea floor terrain have been developed from high resolution (90 metre grid) bathymetric data from the survey in the southern part of the Indian Ocean.
These models show newly discovered sea floor features including:
The identification of these features will assist in navigation during the underwater search.
The data acquired as part of the bathymetric survey has been collected for the sole purpose of finding the missing plane and to bring closure to the families of those on-board. However, as it is some of the first high resolution data available in these areas, it is of great interest to the scientific community and will be released to the public by Geoscience Australia in due course.
For scientists, a greater understanding of deep ocean bathymetry is useful for a range of purposes, including geological interpretation to better understand plate tectonic history; as a baseline product in the creation of hydrodynamic models to gain knowledge on ocean currents and connectivity; the identification of sea floor features; and with the depth of oceans playing a major role in defining the habitat for flora and fauna – to locate areas where unique biological communities may exist.