Mapping the ocean floor

The Geophysical Survey and Mapping (GSM) team work aboard RV Investigator. They operate its extensive array of sonar mapping sensors in support of the collaborative research delivered by our Marine National Facility.

The team oversees the acquisition, processing and management of the vast amounts of seabed data acquired by the ship. Seabed mapping products

The GSM team produce a range of seabed mapping products including 3D seabed models. These models give us a window to the ocean depths and helps scientists to understand some of its hidden secrets.

Seabed mapping products

The GSM team produce a range of seabed mapping products including 3D seabed models. These models give us a window to the ocean depths and helps scientists to understand some of its hidden secrets.

The distribution of seamounts varies considerably across the globe, with the greatest concentration found in the Pacific Ocean, followed by the Atlantic Ocean, Indian Ocean, and to a far lesser extent in the Southern Ocean (where they are rarer and more isolated).

Globally seamounts are estimated to occupy less than 1 per cent of the total area of the ocean floor.

Location

Although most commonly located near tectonic plate boundaries, seamounts are also found in mid-plate regions, where they often form in linear groups known as chains.

Formation

The formation of these seamount chains is linked to hotspots — places where plumes of magma rise through the mantle to the crust.

Many seamounts were once volcanic islands above sea-level but gradually, over millions of years, they sank below the surface of the ocean as the crust below them cooled and became denser.

During this period of subsidence, some underwent prolonged erosion at their summits causing many to have had their tops flattened ⁠— these are called guyots (pronounced gee-yo).

Whilst many people are familiar with the popular seamounts and volcanoes associated with the Hawaiian chain, few are aware of the seamounts in Australian waters.

Extinct volcanoes

The Tasmantid seamount chain is a great example — consisting of 16 extinct volcanoes (some with elevations >4,000 m) and aged from 6 to 40 million years old, this seamount chain spans 2,000 km across the Coral & Tasman Seas. It lies parallel to another seamount chain located further seawards, called the Lord How chain, to which Lord Howe island belongs.

Our research voyages continue to unlock the science behind seamounts.

Learn more about submarine canyons and the tech used to visualise them.

Surrounding Australia are over 750 submarine canyons. These canyons play a crucial role in supporting and regulating our ocean environment.

Extending out from our Australian coastline is the continental shelf, the shallow extension of the Australian landmass. Beyond this shelf the seabed drops steeply down the continental slope onto the abyssal plains.

Within this continental slope deep incisions have been made into the seabed, carving out steep-sided valleys, these are called submarine canyons many of which dwarf their terrestrial counterparts.

Ancient river courses

Some submarine canyons have followed the paths of ancient river courses that meandered their way out to the continental shelf break where ocean currents and landslides have continued their paths creating grand canyons.

Landslides

Other submarine canyons and their tributaries have formed when sections of the continental slope have slipped away over time in a process similar to terrestrial landslides. These submarine landslides, as they are called, create large 'turbity' currents which continue the cycle of seabed erosion and canyon building.

Submarine canyons are considered to be major conduits transporting significant amounts of sediment to the deep ocean floor.

Canyons can also act as conduits for upwelling, a process whereby deep, cold and nutrient rich waters are lifted towards the surface. Upwelling provides a thriving condition for a diverse assortment of marine life.

Bremer Canyon, off the coast of Bremer Bay, WA, is one of Australia’s marine biodiversity hotspots. It starts atop the continental shelf in 100–200 metres of water before plunging to abyssal depths of over 4000 metres. It is home to an abundance of marine life including high numbers of orca, whales and giant squid.

By mapping submarine canyons, we are acquiring data which underpins much of our understanding of these unique and important marine environments.

William’s Ridge is an oceanic ridge which is part of the Kerguelan Plateau in the Southern Ocean.

It is close to Australia’s World Heritage listed Heard and Macdonald Islands.

The ridge was mapped by RV Investigator as part of a 60-day voyage south-west of Australia.

This mapping enabled a comprehensive model of the Ridge to be developed and is helping to better understand the region.

This data will also support Australia in a submission to claim sovereignty over new seafloor under the United Nations Conventions on the Law of the Sea (UNCLOS).

To many people, ancient shipwrecks are fascinating and alluring, often due to the mystery surrounding them and potential riches that they are thought to hold.

For maritime archaeologists however, they are a window into our past and these scientists work at piecing together complex puzzles of human history.

Disappeared without a trace

Many shipwrecks have disappeared without trace and often with a significant loss of life too — sadly these often endure as unsolved mysteries and their stories go untold.

Our research voyages often contribute to the discovery, location and mapping of previously unknown or poorly charted shipwrecks.

Some of the more famous examples include the SS Macumba (located in 2017), SS Federal (mapped in 2019) & the SS Iron Crown (located in 2019).

74 year old mystery solved

Researchers on our research vessel Investigator have solved a maritime mystery 74 years in the making with the discovery of the wreck of SS Macumba, a merchant ship sunk by Japanese air attack during Word War II.

SS Iron Crown sunk by submarine

The SS Iron Crown, a 100 meter-long ore freighter, was sunk by a Japanese submarine on 4 June 1942 while travelling through Bass Strait with a cargo of manganese ore. The heavily loaded freighter was hit by a torpedo from the submarine and sank within 60 seconds.

When ice shelves and glaciers break apart, in a process known as 'calving', they form what we know as icebergs.

Once calved the icebergs are set adrift to float with the ocean currents.

As the ice bergs are formed primarily of freshwater, or pure ice water, they are able to float on the denser seawater.

What lies beneath

The floatation of an iceberg is generally only sufficient to expose a small portion of the iceberg above the surface with the bulk of the volume remaining below the surface.

When an iceberg drifts into shallow waters it’s base, or keel, can come into contact with the seabed.

As an iceberg’s keel contacts the seabed its scrapes out significant gouges in the seabed, and these are referred to as iceberg scours.

Our research voyages to the Southern Ocean, and to the Antarctic ice edge, have allowed for iceberg scours to be mapped in great detail.

By mapping these features we provide valuable data that allows scientists to better understand the worlds ocean currents and climate.