TURBIDITY CURRENTS

Turbidity currents are undersea flows of muddy sediments that are triggered by earthquakes. They generally occur on the continental slope and rise, areas too deep to be affected by surface waves and tidal currents. As the continental slope flattens at its base into the continental rise and the abyssal plains of the deep sea, the turbidity flows slow and the sediments settle into graded beds of sand, silt and mud called "turbidites." The layered greywacke/shales at the base of Ring Mountain are turbidites.

First proposed in the 1930's by Philip Kuenen, a Dutch geologist and oceanographer, the role played by turbidity currents in ocean processes was only widely accepted in the 1950's.

Flume studies have been done on the movement of turbid currents and indirect observations of their existence and actions have been made, including the breakage of undersea telecommunications cables and surface expressions of their occurrence in man made lakes.

We are lucky to have below, one of the only deepsea photos of a turbid current taken from the window of a deep diving submersible. William Dillon, a marine geologist with the USGS took this picture while doing graduate work on the submarine canyons of the East Coast. He has graciously made the slide available to us for posting here. According to Bill, the flows occurred when the submersible touched the wall of the canyon and knocked loose pieces of semi-consolidated sediment, causing the pieces to slide rapidly down the slope....(see note at bottom)
photo interpreted here

This photo was taken on a dive of the research submersible Deepstar 4000 into Block Canyon during the fall of 1967. Block Canyon is a submarine canyon incised into the New England continental shelf SE of the northern end of Long Island. The purpose of these dives to depths of 600 - 800 meters depths in the canyon was to visually document the topographic features and sediment types in the canyon. These observations were made in attempt to consider the processes currently affecting the canyon and it's sediments. A report of the dive and findings can be found in "Erosion by Biological Activity in Two New England Submarine Canyons" by W.P. Dillon and H.B. Zimmerman and published in the Journal of Sedimentary Petrology, Vol 40. No. 2, p. 542-547, June, 1970. A major conclusion of this study was that, at the time of the observations, biological erosion was the dominant force in shaping the canyon and that there was no evidence for down-canyon mass movements of canyon sediments or turbidity currents.

"I looked at the slide on WWW and it looks great - actually better than it did here for color." Bill Dillon, 3/21/95.

Some information on Piera Cava, France and Rhodes turbidites


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latest update: Kathy Klingensmith, 10/23/96