Scientists sampling North Atlantic water found that tritium released into the atmosphere before the 1962 nuclear test ban treaty, mixed downward by 1973. By 1980, the same tritium had moved into deep areas off Florida. Turbidity currents sweep sediment from shallow water to deep Not all currents are predictable.
Turbidity currents are submarine avalanches.
Sediments settle and accumulate in shallow areas like the edges of the continental shelf and slope. Often triggered by an earthquake, they can spill down the continental slope into deep water. Transatlantic telegraph cables snapped from north to south over thirteen hours in 1929, when an earthquake off New England sent sediments slumping and sliding.