Contrary to claims by the mining industry, the seafloor contains a “kaleidoscope of diversity” that we are only just beginning to explore and understand…
Bridie Smith | The Age
The Earth’s seafloor is far more diverse than previously thought, with the first digital map of the planet’s deep sea geological seascape revealing a kaleidoscope of diversity.
It is only the second map of the seafloor, which covers 70 per cent of the Earth’s surface. The first map, below, was hand drawn in the 1970s, had a five-colour key and relied heavily on assumption.
“The original map shows a relatively featureless and barren place where huge tracts of the ocean floor are envisioned to be covered by just one type of sediment,” said geophysicist Dietmar Muller from Sydney University’s school of geosciences.
The 2015 version however uses 13 colours to map the different kinds of sea floor geology – including yellow for sand, red for volcanic rock and pink for shells and coral.
“Our new map brings out the enormous ecological and geological complexity of the seafloor that before we had no idea about,” Professor Muller said.
This digital map, below, reveals just how diverse the planet’s underwater world is.
The project’s lead researcher Adriana Dutkiewicz said the splodges of colour that rim Australia’s coastline almost looked like a piece of Dreamtime art because of the way the “patchwork of dots” hugged the continent’s edge.
Generated from more than 15,000 sea floor samples, the map below records the corals of the Great Barrier Reef in pink. There is also a pink patch relating to shell deposits in the Arafura Sea west of Cape York peninsula, on the south-west corner of Western Australia and on a section of the Great Australian Bight.
The contribution of the Murray-Darling river system is captured below, with the yellow sandy deposits a result of the sediment being washed through the inland basin and out to sea. The brown blotches further out to sea show where the heavier mud and clay sediments have settled.
The map reveals the deep ocean basins are much more complex than previously thought. A lot of the deep sea sediment is formed by the microscopic life that thrives on the sea surface – namely tiny organisms called phytoplankton as seen below. When they die, they drift to the seafloor like marine snow. “The seabed is a recorder of this activity,” Professor Muller said.
The colder waters encircling Antarctica are marked in shades of green on the below map, indicating the sediment is heavily influenced by the cold water-loving phytoplankton known as diatoms. These critters, which are too small to see with the naked eye, have silica shells which after they die accumulate on the seafloor, locking away carbon.
Diatoms are among the most important aquatic micro-organisms – they produce about a quarter of the oxygen we breathe and make a bigger contribution to fighting global warming than most land-based plants.
For this reason Professor Muller said the seafloor geology map also doubles as a map of the planet’s underwater carbon sinks, which will provide an invaluable insight into how oceans have responded in the past to climate change.
Published in the journal Geology, the map could also become an unexpected aid in the search for missing Malaysian Airlines flight MH370 because it plots the type of sediments covering the seafloor of the southern Indian Ocean, as seen in the map below.
“Our map could help reveal how quickly the debris might become covered with marine sediment,” Professor Muller said. “In some regions such as the brown areas, sedimentation rates are very slow…so if the plane went down in a brown area then you could still probably find it in decades to come.”