Between the two zones lies a row of Klippen, while towards the Hungarian plain the inner zone is bordered by a fringe of volcanic eruptions of Tertiary age.
The Klippen are isolated hills, chiefly of Jurassic limestone, rising up in the midst of the later and softer deposits on the inner border of the sandstone zone.
The so-called Klippen of the Swiss Alps are now usually supposed to rest upon thrustplanes, but they are not strictly analogous, either in structure or in position, with those of the Carpathians.
These are the Klippen, and they are especially important in the Chablais and between the Lakes of Geneva and Thun.
Not only is the folding of the Klippen wholly independent of that of the zone in which they lie, but the rocks which form them are of foreign facies.
The Klippen are, no doubt, the remains of a much larger mass brought into the region upon a thrust-plane, and much of the Molasse has been derived from its destruction.
Although the explanation here given of the origin of the Swiss Klippen is that which now is usually accepted, it should be mentioned that other theories have been proposed to account for their peculiarities.