Sediment from the Columbia River migrated to the north on ocean tides and formed the Long Beach peninsula, which is still growing actively.
Washington state boasts volcanoes from the north to the south have made history. Few years ago, underwater volcanoes were erupted and the released lava was cooled into basalt and made on the ocean floor.
The layer of those sediment built up the tectonic plate below the ocean depths. Then, a shift occurred and the floor of the ocean shifted with the larger tectonic plate.
The larger tectonic plate can move away from each other, parallel to each other, or into to each other.
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