The Student's Elements of GeologyLyell, Charles, Sir
Science
The Student's Elements of Geology
Lyell, Charles, Sir
Geology
Glaciation of Scandinavia and Russia.—In large tracts of Norway and
Sweden, where there have been no glaciers in historical times, the
signs of ice-action have been traced as high as 6000 feet above the
level of the sea. These signs consist chiefly of polished and furrowed
rock-surfaces, of moraines and erratic blocks. The direction of the
erratics, like that of the furrows, has usually been conformable to the
course of the principal valleys; but the lines of both sometimes
radiate outward in all directions from the highest land, in a manner
which is only explicable by the hypothesis above alluded to of a
general envelope of continental ice, like that of Greenland (page 170).
Some of the far-transported blocks have been carried from the central
parts of Scandinavia towards the Polar regions; others southward to
Denmark; some south-westward, to the coast of Norfolk in England;
others south-eastward, to Germany, Poland, and Russia.
In the immediate neighbourhood of Upsala, in Sweden, I had observed, in
1834, a ridge of stratified sand and gravel, in the midst of which
occurs a layer of marl, evidently formed originally at the bottom of
the Baltic, by the slow growth of the mussel, cockle, and other marine
shells of living species, intermixed with some proper to fresh water.
The marine shells are all of dwarfish size, like those now inhabiting
the brackish waters of the Baltic; and the marl, in which many of them
are imbedded, is now raised more than 100 feet above the level of the
Gulf of Bothnia. Upon the top of this ridge repose several huge
erratics, consisting of gneiss for the most part unrounded, from nine
to sixteen feet in diameter, and which must have been brought into
their present position since the time when the neighbouring gulf was
already characterised by its peculiar fauna. Here, therefore, we have
proof that the transport of erratics continued to take place, not
merely when the sea was inhabited by the existing testacea, but when
the north of Europe had already assumed that remarkable feature of its
physical geography which separates the Baltic from the North Sea, and
causes the Gulf of Bothnia to have only one-fourth of the saltness
belonging to the ocean. In Denmark, also, recent shells have been found
in stratified beds, closely associated with the boulder clay.
Glaciation of Scotland.—Mr. T. F. Jamieson, in 1858, adduced a great
body of facts to prove that the Grampians once sent down glaciers from
the central regions in all directions towards the sea. “The glacial
grooves,” he observed, “radiate outward from the central heights
towards all points of the compass, though they do not always strictly
conform to the actual shape and contour of the minor valleys and
ridges.”
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