more frequently, form elevations, as in Figs. 44, 45. In every case, however, the evidence of denudation

FIG. 46. SECTION ACROSS THE NORTHERN LIMESTONE ALPS (E. Fraas). 1, Crystalline schists; 2, Permian; 3, Bunter; 4, Muschelkalk; 5, Limestone (Wettersteinkalk); 6, Dolomite; 7, Jurassic and Cretaceous.

is conspicuous. Nor is this less clearly seen in the more complicated structures of the Alps. In the fol

Zointe de la Houille

FIG. 47. SECTION ACROSS THE DIABLERETS (Renevier).
Tertiary strata showing a succession of overfolds.

lowing section, for example (Fig. 46), we have a series of various calcareous strata and underlying schists compressed into folds and dislocated, the tops of the

anticlines having in each case been removed. Take again the section of the Diablerets (Fig. 47), in which the Tertiary strata are doubled back upon themselves

FIG. 48.

SECTION ACROSS DENT DE MORCLES (Renevier).

1, Schistose rocks, etc. ; 2, Carboniferous strata; 3. Jurassic strata; 4, Cretaceous strata; 5, Tertiary strata; , S, S, Cretaceous and Tertiary rocks inverted; 7, thrust-plane.

in a series of sharp overturned flexures.

overturned flexures. A similar, but somewhat more complicated, structure appears in the Dent de Morcles (Fig. 48), where the remarkable

FIG. 49.

INVERSION AND OVERTHRUST IN THE MOUNTAINS SOUTH OF THE
LAKE OF WALLENSTADT (E. Fraas, after A. Heim).

s, Schistose rocks; p, Permian; wj, bj, Jurassic; c, Cretaceous; e, Eocene. The Permian strata (p) are turned upside-down and thrust upward over the contorted Eocene (e).

Here,

overturn flexure rests upon a thrust-plane. again, the strata, it will be observed, are doubled back upon themselves, or turned upside-down. Obviously these mountains are monuments of excessive erosion.

Similar evidence of vast rock-removal is furnished by the remarkable double-folds and overthrusts in the mountains of the Cantons Glarus and St. Gall, as described by Heim and others (See Fig. 49.)

Similar conclusions may be drawn from the appearances presented by every kind of rock-structure throughout the whole extent of the Alps.

In the Jura mountains the rock-foldings are sometimes symmetrical, and anticlines and synclines now and again coincide with hills and valleys respectively, as in Fig. 50.

It will be observed, however, that the synclinal strata have suffered less erosion than the intervening

SE

Ballsthal

Münster

Ramenz

BW

FIG. 50.

SYMMETRICAL FLEXURES OF THE JURA MOUNTAINS.
Anticlinal mountains and synclinal valleys.

anticlinal strata. In the western part of the same range of mountains the folds are less symmetrical, but they yield the same evidence of denudation. The accompanying section (Fig. 51, p. 116) shows, indeed, that the saddlebacks have not only been considerably reduced, but are even beginning to develop into valleys; while the synclines, on the other hand, have experienced less erosion, those with approximately vertical axes appearing as dominant heights.

Excellent examples of the same phenomena are furnished by the Carpathians-a mountain-chain also

Chanu du Dombief

S.W

Kiesorna

Ruski Put

of relatively recent age. Fig. 52
(p. 116) exhibits the structure of
a part of the chain in which the
folds are unsymmetrical. Here
it will be observed that the tops of
the anticlines have in every case
been greatly reduced; but the
synclines, owing to the isoclinal
arrangements of the strata, do
not tend to develop into hills.
In point of fact, unsymmetrically
folded strata behave very much.
in the same way as beds having
a persistent dip in one direction.
When the anticlines have been
truncated the strata appear at
the surface as a series of isoclinal
beds, some of which are rela-
tively more resistant than others.
In time, therefore, these harder
beds crop out as well-marked
ridges or escarpments, according
as the angle of dip is high or rela-
tively low. But no sooner do
the axes of the folds approach the
vertical, and the flexures become
symmetrical, than the superior
strength of the synclinal structure
at once asserts itself. This is well
illustrated by Fig. 53, where we have a series of

Libuchora

NC.

Siezki

FIG. 53. SECTION ACROSS PART OF THE MIDDLE CARPATHIANS (Vacek).

Symmetrical synclines forming mountains. This section crosses another portion of the Sandston Zone shown in Fig. 52.

syn