GoKawiilThe bottom of the ocean has been mapped in much less detail than has the surface of Mars.Credit: US Geological Survey/Science Photo Library
The ocean’s depths are among the ultimate frontiers for scientific exploration. Scientists have visually surveyed less than 0.001% of the sea floor, yet oceanography is essential to understanding the climate, ecosystems and processes of deep Earth — including earthquakes and the resulting tsunamis.
Now, emerging technologies, including advanced drilling technologies, seismic sensors and methods to convert deep-sea cables into a giant seismic-surveillance network, are poised to crack open these mysteries.
Nature has looked into how some of these tools work, and the geoscience questions that they could help to answer.
Mapping the mantle
Plate tectonics is driven by convection, or the churning of the mantle — the layer of mostly solid rock under Earth’s crust that makes up more than 80% of the planet’s volume. But the mantle’s inner geological workings remain mostly a mystery.
Researchers have begun to map the process of convection by measuring how different rock densities affect the propagation of seismic waves — using ocean-bottom seismometers (OBSs) that can run on batteries for one year or more.
OBS studies have helped to show that the motion of rock in the mantle is “like a lava lamp”, says Ana Ferreira, a seismologist at University College London (UCL). “Imagine a pan with boiling syrup, but different types of syrup of different densities,” she says. Particularly hot ‘plumes’ (solid mantle rock that's hotter than the surrounding mantle) create mid-ocean chains of volcanoes, such as those in Iceland or the Hawaiian archipelago.
Researchers have used ocean-bottom seismometers, shown here being lowered into the water, to study Earth’s mantle. Credit: NASA Image Collection/Alamy
Pioneering research in the 1990s focused on the Pacific Ocean, but scientists are now expanding their studies to the rest of the oceans. One such project, called UPFLOW, is currently analysing the data from OBSs that Ferreira and her collaborators deployed in the Atlantic around the Azores, Canary Islands and Madeira.
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