Page:Submerged forests (1913).djvu/43

III] the tidal oscillation to such an extent that its range is much greater outside the bank than within.

If these submerged outer banks were to be swept away by some change in the set of the currents, large areas now cultivated and inhabited would be flooded by salt water at every spring tide, and the turf of the meadows would be covered by a layer of marine silt, such as we see alternating with the submerged forests in the docks of the Thames. Such alternations, if thin, do not necessarily prove a change in the level of the sea; they may only point to the alternate accumulation and removal of sand-banks in a distant part of the estuary.

The Norfolk coast trends westward soon after leaving Cromer, and where the cliff seems to pass inland at Weybourn we enter an ancient valley, one side of which has been entirely cut away by the sea, except for a few relics of the further bank, now included in the shingle beach which runs out to sea nearly parallel with the coast and protects Blakeney Harbour. Here again we find that in the bottom of the valley there must be a submerged forest, for slabs of peat are often thrown up at Weybourn, and by the use of a grapnel the peat was found in place off Weybourn at a depth of several fathoms.

When the coast turns southward again, and the wide bay of the Wash is entered, we find an extensive development of submerged land-surfaces and peat