Sediment movement on the continental shelf near Washington and Oregon

The nuclides zinc-65 and cobalt-60 associated with river-borne particulate matter are incorporated in sediment on the Continental Shelf near the Colum- ia River. Changes in the relative concentrations of zinc-65 and cobalt-60 and in the ratio of the activity of zinc-65 and cobalt-60 suggest that radioactive sediment moves northward 12 to 30 kilometers per year along the shelf and 2.5 to 10 kilometers per year westward away from the coast.