After the subsidence came another period of uplift, possibly still in progress.
The continental shelves include not only the oceanic border of the continents but also great areas of the enclosed seas and particularly of the fringing seas, the origin of which through secular subsidence is often very clearly apparent, as for instance in the North Sea and the tract lying off the mouth of the English Channel.
The lower Hudson, below Troy, is really a fiord, the stream valley being drowned by the sea through subsidence of the land.
A still greater subsidence farther north produced Puget Sound.
In many places there are different channels for high and low water, the latter being partly filled by each freshet, and recut after each subsidence; and the river meanders tortuously through the alluvial bottom in scores of great bends, loops and cut-offs.