ABICh's geological sketches beyond the CAUCASUS. 41 



Geological Sketches from the Provinces beyond the Caucasus. By 

 Professor Abich. — Geologische Skizzen aus Transcaucasien, Vom 

 Herm Professor Abich * . 



[Read before the Imp. Academy, April 17f 1846.] 



[Bull, de la Classe Phys. Mathem. de I'Acad. Imp. des Sciences de St. Petersbom-g.] 



On the Volcanic Plateaux of the Lower Caucasus. 



In attempting to describe the physical geography of the mountain 

 districts which extend south of the Caucasus, between the Black Sea 

 and the Caspian, we find great difficulty in applying one or more 

 general appellations to the many ramifications of this mountainous 

 region ; principally because well-combined geological investigations 

 have not yet been extended to Asia Minor. The great natural causes 

 which have given a peculiar physical character to the simple features 

 of the surface of these districts, modifying even their historical im- 

 portance, are the results of geological developments, chiefly owing to 

 forces acting from the centre towards the surface of the earth. By 

 the agency of these processes, which succeeded one another at defi- 

 nite periods, similar natural forms were produced from similar ele- 

 ments, and were spread in connexion with one another according to 

 the same law over vast spaces. These propositions, which a geolo- 

 gical description of the uplands of Armenia will establish, prove the 

 subterranean connexion of all parts of the above-mentioned mountain 

 groups, and justify the scientific propriety of a common name for 

 them. The choice of this name is optional ; yet as there are im- 

 portant practical reasons for maintaining the geological union of this 

 mountain group with the Caucasus, it appears most natural to assume 

 on the isthmus between the two seas, an upper and a loiver Caucasus, 

 and in the first place to limit the latter term to the mountain district 

 which is comprised in the almost elliptical space enclosed by the Araxes 

 on the one side and by the Kur on the other. It will not be possi- 

 ble to give a more exact definition of the extent and the boundaries 

 of the Lower Caucasus until more accurate geological investigations 

 shall have been extended over the whole of Grusia. 



The Lower Caucasus. — It is remarkable that this lofty mountain 

 chain, so richly provided with every variety of physical productions, 

 with its lofty summits 12,000 feet above the sea, should be below the 

 limits of perpetual snow, while the summits of the Elburuz and the 

 Kasbek, at a height of 10,380 and 9950 French feet, are above it. 

 The principal ranges of this momitain chain are parallel with those of 

 the upper and real Caucasus. Along a line which may be said to 

 represent the principal portion of this mountain chain, it is traversed 

 by a succession of table-lands connected with one another, having a 

 considerable, though not always the same mean elevation above 

 the sea. The rocks of which they consist have been brought to the 

 surface of the earth in an igneous or molten state. These volcanic 

 masses burst forth in the centre of those mountains, the heights of 

 which they now cover, as with a mantle, with undulating nearly hori- 



* See Journal of the Geol. Soc. vol. ii. part ii. p. 93. 



