'Smart boulders' record huge underwater avalanche

[nitpicker]

http://www.bbc.com/news/science-environment-38310108

'Smart boulders' record huge underwater avalanche

By Jonathan Amos
BBC Science Correspondent, San Francisco

13 December 2016

From the section Science & Environment


Scientists have had a remarkable close-up encounter with a gigantic underwater avalanche. It is the first time researchers have had instruments in place to monitor so large a flow of sediment as it careered down-slope.

The event occurred in Monterey Canyon off the coast of California in January. The mass of sand and rock kept moving for more than 50km, as it slipped from a point less than 300m below the sea surface to a depth of over 1,800m. Speeds during the descent reached over 8m per second. An international team running the Coordinated Canyon Experiment (CCE) is now sitting on a wealth of data.
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One recent innovation is the Benthic Event Detector (BED). "Think 'smart boulder'," said MBARI’s Prof Charlie Paull, who gave details of the 15 January event here at the Fall Meeting of the American Geophysical Union. "The BED is a 44cm sphere. It has an electronic package entombed within in it; it measures pressure and orientation, and will record how it moves down the canyon floor. And we use the BEDs to see the progression of the turbidity current as it rolls over one BED after another," he told BBC News.

The force of these colossal flows of sediment has been known to sever the underwater cables that carry telecommunications around the globe. It was no surprise therefore to hear that the CCE’s instruments had an extremely rough ride on 15 January. Some sensors with anchors weighing more than a tonne were dragged 7km down the canyon. But what they recorded will be invaluable to the scientists as they seek to learn more about how turbidity currents are triggered, and how they actually work; how the material - what amounts to a kind of slurry - moves along the seafloor.
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