1. _Slow Depression and Upheaval._--On the west side of Japan the land
is believed to be sinking below the sea, for fields are replaced by
beaches of sand or shingle, while the depth of the sea off shore has
perceptibly increased. A subsidence of the south of Sweden has taken
place in comparatively recent times, for streets and foundations of
houses at successive levels are found below high-water mark. The west
coast of Greenland over an extent of more than 600 m. is sinking, and
old settlements are now submerged. Proofs of submergence of land are
furnished by "submerged forests," and beds of terrestrial peat now
lying at various depths below the level of the sea, of which many
examples have been collected along the shores of the British Isles,
Holland and France. Interesting evidence that the west of Europe now
stands at a lower level than it did at a late geological period is
supplied in the charts of the North Sea and Atlantic, which show that
the valleys of the land are prolonged under the sea. These valleys
have been eroded out of the rocks by the streams which flow in them,
and the depth of their submerged portions below the sea level affords
an indication of the extent of the subsidence.
The uprise of land has been detected in various parts of the world.
One of the most celebrated instances is that of the shores of the Gulf
of Bothnia, where, at Stockholm, the elevation, between the years 1774
and 1875, appears to have been 48 centimetres (18-1/2 in.) in a
century. But on the west side of Sweden, fronting the Skager Rak, the
coast, between the years 1820 and 1870, rose 30 centimetres, which is
at the rate of 60 centimetres, or nearly 2 ft. in a century. In the
region of the Great Lakes in the interior of Canada and the United
States it has been ascertained that the land is undergoing a slow tilt
towards the south-west, of which the mean rate appears to be rather
less than 6 in. in a century. If this rate of change should continue
the waters of Lake Michigan, owing to the progress of the tilt, will,
in some 500 or 600 years, submerge the city of Chicago, and eventually
the drainage of the lakes will be diverted into the basin of the
Mississippi. Proof of recent emergence of land is supplied by what are
called "raised beaches" or "strand-lines," that is, lines of former
shores marked by sheets of littoral deposits, or platforms cut by
shore-waves in rock and flanked by old sea-cliffs and lines of
sea-worn caves. Admirable examples of these features are to be seen
along the west coast of Europe from the south of England to the north
of Norway. These lines of old shores become fainter in proportion to
their antiquity. In Britain they occur at various heights, the
platforms at 25, 50 and 100 ft. being well marked.
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