Avalanches happen under the sea too. A turbidity current is a rapid downhill rush of water made dense by the sediment it carries — and it can reshape the seafloor, carving underwater canyons as it goes.
Turbidity currents can be set off by earthquakes, collapsing slopes and other geological disturbances, and can change the shape of the seafloor. Credit: NOAA.
What turbidity is
Turbidity measures how much material — sediment, plankton, organic by-products — is suspended in a body of water. The more of these light-blocking particles there are, the denser and cloudier the water becomes.
How a turbidity current starts
Earthquakes, collapsing slopes and other geological disturbances can loosen mud and sand on the continental shelf. The cloudy, heavy water then rushes downhill like an avalanche, picking up more sediment and speeding up as it flows.
What it leaves behind
Turbidity currents erode large areas of the seafloor and can create underwater canyons. They also drop huge amounts of sediment wherever they flow, usually in a graded fan: the largest particles at the bottom, the smallest on top.
How scientists study them
NOAA scientists attach turbidity sensors to current meters to collect data near underwater volcanoes and other very active geological sites. Satellite imagery measures turbidity from above, by gauging how much light a patch of water reflects.
Sources
Based on "What is a turbidity current?" from NOAA's National Ocean Service, a work of the United States government in the public domain.
Licence: CC0 1.0 (public domain) · Adapted from oceanservice.noaa.gov
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