Remarks on the Grand banks turbidity current

Kullenberg, B.

doi:10.1016/0146-6313(54)90002-7

Cited by 9 publications

(4 citation statements)

References 5 publications

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“…Subsequent breaks between the original break and shore station can be detected only as a drop in resistivity (Kullenberg, 1954). Thus, the time of the first break will always be known, but the second and subsequent ones may not be detected.…”

Section: Significance Of Reported Breaksmentioning

confidence: 97%

The 1929 “Grand Banks” earthquake, slump, and turbidity current

Piper

Shor²,

Clarke³

1988

Geological Society of America Special Papers

129

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The epicenter of the 1929 "Grand Banks" earthquake (Ms = 7.2) was on the continental slope above the Laurentian Fan. The zone in which cables broke instantaneously due to the earthquake is characterized by surface slumping up to 100 km from the epicenter as shown by sidescan sonographs and seismic reflection profiles. The uppermost continental slope, however, is almost undisturbed and is underlain by till deposited from grounded ice. The Eastern Valley of the Laurentian Fan contains surficial gravels molded into large sediment waves, believed to have formed during the passage of the 1929 turbidity current. Sand sheets and ribbons overlie gravel waves in the lower reaches of Eastern Valley. Cable-break times indicate a maximum flow velocity of 67 km/hr (19 m/s). The occurrence of erosional lineations and gravel on valley walls and low intravalley ridges suggest that the turbidity current was several hundred meters thick. The current deposited at least 175 km 3 of sediment, primarily in a vast lobe on the northern Sohm AbyssalPlain where a bed more than 1 m thick contains material ranging in size from gravel to coarse silt.There is no apparent source for so much coarse sediment on the slumped areas of the muddy continental slope. We therefore infer that there was a large volume of sand and gravel available in the upper fan valley deposits before the earthquake. This coarse sediment was discharged from sub-glacial meltwater streams when the major ice outlet through the Laurentian Channel was grounded on the upper slope during middle Wisconsinan time. This sediment liquefied during the 1929 event, and the resulting flow was augmented by slumping of proglacial silts and gas-charged Holocene mud on the slope.

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Section: Significance Of Reported Breaksmentioning

confidence: 97%

The 1929 “Grand Banks” earthquake, slump, and turbidity current

Piper

Shor²,

Clarke³

1988

Geological Society of America Special Papers

129

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“…Shepard (1954) based his objections largely on the claim that the velocities of 10-50 knots were larger than could be expected, but offered no more serious objections. Kullenberg (1954) misled by some erroneous soundings claimed that Heezen and Ewing's explanation required the turbidity current to run uphill and over a range of hills, an ability which, he correctly pointed out, could not be attributed to turbidity currents. However, subsequent exploration confirmed Heezen and Ewing's belief that the alleged mountain range was the result of poor contouring of bad soundings.…”

Section: Dynamic Processes Of Abyssal Sedimentationmentioning

confidence: 99%

Dynamic Processes of Abyssal Sedimentation: Erosion, Transportation, and Redeposition on the Deep-sea floor

Heezen

1959

Geophys J Int

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The concept of a quiet, nearly motionless, and certainly currentless deep-sea floor lacking the processes of erosion so prevalent in shallower seas was well ingrained in scientific thought until discoveries of the past decade revised this serene and static picture. The new concept is a more dynamic one in which submarine landslides, raging turbidity currents, internal tides, deep-sea current scour, and submarine postdepositional solution and alteration play a part in shaping the sea floor, in disturbing and nurturing its fauna and which produce sedimentary structures and distributions formerly thought to be the exclusive mark of shallow water deposits. The concepts involved are still in a critical state of flux with many conflicting viewpoints as to the processes involved and their relative importance. The development of the major concepts is traced and the principal variant viewpoints are briefly reviewed. Part I. Early ideasThe Naked Abyss. "The geological clock may strike new periods; its hands may point to era after era; but, so long as the ocean remains in its basin-so long as its bottom is covered with blue water-so long must the deep furrows and strong contrasts in the solid crust below stand out bold, ragged, and grand. Nothing can fill up the hollows there; no agent now at work, that we know of, can descend into its depths, and level off the floors of the sea." (Maury 1855.) Thus M. F. Maury eloquently summed up the view generally held a century ago. Remembering the then newly discovered deep-sea oozes he added:"But it now seems that we forgot the oceans of animalculae . . . whose remains in vast multitudes sink down and settle upon the bottom."The Unremitting Snowfall. The concept of the great unremitting snowfall which modified and then replaced the original picture of a naked abyss was stated clearly by Rachel Carson:"When I think of the floor of the deep sea, the single overwhelming fact that possesses my imagination is the accumulation of sediments. I see the steady, unremitting, downward drift of material from above, flake upon flake, layer upon layer-a drift that has continued for hundreds of millions of years, that will go on as long as there are seas and continents.'' Dynamic processes of abyssal sedimentation 143 Large elements of truth are found in both of these seemingly contradictory concepts which is why both have so long endured. To be sure, sedimentation is so slow over vast areas of the ocean floor that the original "grand and imposing'' relief mentioned by Maury is, over broad areas of the sea floor, still to be observed only slightly modified by subsequent deposition (Heezen, Tharp & Ewing 1959). Furthermore, the success which students of sediments have had in reading that "epic poem of earth history" contained in the successive layers of sediment further attests to the general validity of the concept of the unremitting snowfall (Phleger 1952, Ericson et al., in press, Broecker, Turekian & Heezen 1958. However, neither of these concepts tells the complete story; nature is considerably ...

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“…Doubtless a slide starting on a steep slope would eventually grade into a turbidity current, but there must be a great diff'erence in energy at the start as well as in the mechanics of their motion and their erosive power. Witness the conflict of opinion over the velocities and even the type of the Grand Banks " flow " which parted the Western Union cables following the earthquake of 1928 (Kullenberg, 1954). Possibly this may seem academic, but when the term " turbidity current " is mentioned many people visualize a suspension current such as flows along the bottom of Lake Mead or in the Swiss lakes.…”

Section: Turbidity Currents and Slope Topographymentioning

confidence: 99%

“…Its position and intensity will depend on the relation of the analyzer axis to the Small percentages of polarization of the order of 5% may readily be delected. The instrument has, therefore, proved useful in addition to its present application in monitoring the illumination of experimental apparatus where polarization of the light source or stray polarized light in the system had to be avoided (Wahrman 1950;1954 b).…”

Section: Introductionmentioning

confidence: 99%

Papers in marine biology and oceanography, dedicated to Henry Bryant Bigelow by his former students and associates on the occasion of the twenty-fifth anniversary of the founding of the Woods Hole Oceanographic Institution, 1955.

1955

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Damage to fish food species trawled over in the main area of the North Sea plaice, cannot be serious; otherwise there would be a noticeable diflFcrence where trawling is impossible, as close to light vessels or among the under-water sand dunes.Direct attack, covering the ground some five or six times over on the average, did break full-grown Heart Urchins, Echinocardium cordatum, and possibly swimming or paddlcr crabs (Portunus dcpuraior), but appeared not to damage Ophiura albida, nor any of the fragile-shelled plaice food animals: razor shells, Mactra or Tellina. Those forms were not very abundant, but all the 15 specimens taken of fragile animals (other than urchins and paddlers) were undamaged. Such large urchins as were damaged were not plaice food. Doubtless Sabellaria habitations (ross) would be broken and laid low, but they would probably soon be reconstructed.Trawling, even with a tickler chain, seems again to escape the so viable indictment.

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Remarks on the Grand banks turbidity current

Cited by 9 publications

References 5 publications

The 1929 “Grand Banks” earthquake, slump, and turbidity current

The 1929 “Grand Banks” earthquake, slump, and turbidity current

Dynamic Processes of Abyssal Sedimentation: Erosion, Transportation, and Redeposition on the Deep-sea floor

Papers in marine biology and oceanography, dedicated to Henry Bryant Bigelow by his former students and associates on the occasion of the twenty-fifth anniversary of the founding of the Woods Hole Oceanographic Institution, 1955.

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