Cape Disappointment gold is unique in that it is believed that this gold has traveled a long distance to find its way back to the beach.
Gold from the Columbia River and other ocean bound waterways dump a great deal of gold into the ocean every year. The surf in turn drives this gold back onto the shore and deposits just like any other placer deposit.
Think of the Gold at the Cape like flood gold, water pushes the gold until it drops out in a slow spot or is trapped and there is not enough pressure to continue moving the gold and it begins concentrating and sinking into the black sands. With the upper layer black sands staying somewhat loose with the tide, the deeper hard-packed sands allow the gold to settle in. The key to successful prospecting on the beach is to find the areas where the gold deposited and is protected from the tidal action.