The Beauties of Nature, and the Wonders of the World We Live In

by Sir John Lubbock

In the Alps the contortions are much greater than in the Jura. Fig. 19 shows a section after Heim, from the Spitzen across the Brunnialp, and the Maderanerthal. It is obvious that the valleys are due mainly to erosion, that the Maderaner valley has been cut out of the crystalline rocks s, and was once covered by the Jurassic strata j, which must have formerly passed in a great arch over what is now the valley.

However improbable it may seem that so great an amount of rock should have disappeared, evidence is conclusive. Ramsay has shown that in some parts of Wales not less than 29,000 feet have been removed, while there is strong reason for the belief that in Switzerland an amount has been carried away equal to the present height of the mountains; though of course it does not follow that the Alps were once twice as high as they are at present, because elevation and erosion must have gone on contemporaneously.

Fig. 19.—e, Eocene strata; j, Jurassic; s, Crystalline rocks.

It has been calculated that the strata between Bâle and the St. Gotthard have been compressed from 202 miles to 130 miles, the Ardennes from 50 to 25 miles, and the Appalachians from 153 miles to 65! Prof. Gumbel has recently expressed the opinion that the main force to which the elevation of the Alps was due acted along the main axis of elevation. Exactly the opposite inference would seem really to follow from the facts. If the centre of force were along the axis of elevation, the result would, as Suess and Heim have pointed out, be to extend, not to compress, the strata; and the folds would remain quite unaccounted for. The suggestion of compression is on the contrary consistent with the main features of Swiss geography. The principal axis follows a curved line from the Maritime Alps towards the north-east by Mont Blanc and Monte Rosa and St. Gotthard to the mountains overlooking the Engadine. The geological strata follow the same direction. North of a line running through Chambery, Yverdun, Neuchâtel, Solothurn, and Olten to Waldshut on the Rhine are Jurassic strata; between that line and a second nearly parallel and running through Annecy, Vevey, Lucerne, Wesen, Appenzell, and Bregenz on the Lake of Constance, is the lowland occupied by later Tertiary strata; between this second line and another passing through Albertville, St. Maurice, Lenk, Meiringen, and Altdorf lies a more or less broken band of older Tertiary strata; south of which are a Cretaceous zone, one of Jurassic age, then a band of crystalline rocks, while the central core, so to say, of the Alps, as for instance at St. Gotthard, consists mainly of gneiss or granite. The sedimentary deposits reappear south of the Alps, and in the opinion of some high authorities, as, for instance, of Bonney and Heim, passed continuously over the intervening regions. The last great upheaval commenced after the Miocene period, and continued through the Pliocene. Miocene strata attain in the Righi a height of 6000 feet.

For neither the hills nor the mountains are everlasting, or of the same age.

The Welsh mountains are older than the Vosges, the Vosges than the Pyrenees, the Pyrenees than the Alps, and the Alps than the Andes, which indeed are still rising; so that if our English mountains are less imposing so far as mere height is concerned, they are most venerable from their great antiquity.

But though the existing Alps are in one sense, and speaking geologically, very recent, there is strong reason for believing that there was a chain of lofty mountains there long previously. "The first indication," says Judd, "of the existence of a line of weakness in this portion of the earth's crust is found towards the close of the Permian period, when a series of volcanic outbursts on the very grandest scale took place" along a line nearly following that of the present Alps, and led to the formation of a range of mountains, which, in his opinion, must have been at least 8000 to 9000 feet high. Ramsay and Bonney have also given strong reasons for believing that the present line of the Alps was, at a still earlier period, occupied by a range of mountains no less lofty than those of to-day. Thus then, though the present Alps are comparatively speaking so recent, there are good grounds for the belief that they were preceded by one or more earlier ranges, once as lofty as they are now, but which were more or less completely levelled by the action of air and water, just as is happening now to the present mountain ranges.

Movements of elevation and subsidence are still going on in various parts of the world. Scandinavia is rising in the north, and sinking at the south. South America is rising on the west and sinking in the east, rotating in fact on its axis, like some stupendous pendulum.