Bathymetry is the study of seafloor features. Many
bathymetric maps contain only basic details and large areas of the oceans
remain poorly mapped.
First map of the ocean floor
When Alfred Wegener came up with his theory of continental
drift, no one knew what lay beneath the waves. Some harbours had been mapped,
but the vast oceans remained unexplored. Sonar (SOund NAvigation and Ranging)
technology allowed people to measure the depth of oceans. With the help of improved
sonar developed in World War II, the mapping began.
Compiling hundreds of thousands of data points from hundreds
of ocean voyages was a daunting task, before the advent of modern computing. In
1957, Heezen and Tharp published the first map of the seafloor that allowed the
public to visualise the floor of the North Atlantic. Early maps like these were
vital to the modern theory of plate tectonics. They showed the locations of
mid-ocean ridges, deep trenches and submerged volcanic arcs. People could
finally see how the oceans grow and where plates subduct.
This painting of
the mid-ocean ridges is based on the scientific mapping of Marie Tharp and
Bruce Heezen (H Berann 1977, public domain)
Video:
- The history of seabed mapping
(RealSim Movies)
Website:
- History of seafloor mapping
(NOAA)
Why bother with bathymetry?
The stunning maps created by Tharp and Heezen give the
impression that the ocean depths have been adequately mapped. However, this is
not the case. We have more detailed maps of the Moon, Mars and Venus, than of the
seafloor.
The largest structures (e.g. mid-ocean ridges) have been
mapped, but there is still much to be learnt. This was highlighted in 2014,
when flight MH370 was presumably lost in the southern Indian Ocean. Detailed
bathymetric surveys were made of areas off Western Australia and scientists
discovered that the seafloor was much more rugged than previously thought. They
found many new hills and mountains, as well as four times more seamounts than
previously mapped. The new features aid our understanding of seafloor spreading
and highlight areas of potential biodiversity.
3D bathymetry
image from the search area for flight MH370 (ATSB, photo by ABIS C Beerens,
RAN, 2014, Wikimedia Creative Commons)
Video:
- Mapping the deep ocean: Geoscience Australia and the search for MH370
(Geoscience Australia)
Website:
- MH370:Bathymetric Survey
(ATSB)
Seabed 2030
In 2017, the Seabed 2030 project was launched. The project
is an international effort coordinated by General Bathymetric Chart of the
Oceans (Gebco). This map will be a tool for management and conservation,
disaster planning, scientific understanding and resource extraction.
The organisation is encouraging all ocean-going vessels, from
cargo ships to recreational vessels, to transmit their sonar data in real time to
the British Oceanographic Data Centre. The Centre is coordinating the mapping
effort and allowing access to the data. Marine enthusiasts can propose names
for underwater features by writing to the International Hydrographic
Organisation in Monaco.
Multibeam sonar provides detailed maps of the seafloor
that contribute to the Seabed 2030 project (Illustration of underwater mapping
capability of USNS Bowditch, US Navy graphic illustration, public domain)
Video:
Websites:
Explore the ocean depths from home
- Try your hand at mapping a simulated seafloor as shown in the AusEarthEd video What Lies Beneath?
- Explore the oceans with Google Earth or NOAA’s Bathymetric Data Viewer.
- Take a close look at coral reefs with the Living Oceans Foundation.