A seismic reflection profile in 1961, south of Grand Banks, showed a huge gravity slump on the continental slope near the first of a sequence of delayed cable breaks believed to be due to a turbidity current from the 1929 earthquake. This great slump could explain the instantaneous cable breaks near the epicenterter. Sedimentary cores show generally a gray layer over a thick red layer, but in channels inferred to be made by turbidity currents associated with the Grand Banks earthquake the gray layer is thinner or absent. The change in color is thought due to the red sediments having been abruptly cut off from their source, perhaps by glacial retreat or sea-level rise.--G.D.C

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