average breadth of 4o or 5o miles, extends for 350 miles to the Afghan frontier. My own knowledge of the range is based on three caravan journeys—one into the high mountains south of Askhabad ; another around the eastern end of the range from Dushak, where the railroad turns away from the mountains, to Serakhs and up the Hen Rud ; and a third from Meshed, via Kuchan, to Askhabad.
Kopet Dagh appears to be a fairly mature mountain mass which has recently been faulted and strongly uplifted, and thus rejuvenated. The highest portion, near Askhabad, has been described by Professor Davis (ante, p. 46). Farther to the east the mountains present the saine flat-topped appearance, with young valleys cut sharply into structural slopes which must have assumed their present smooth character during Tertiary times, when the mountains stood lower. This is well illustrated in the back slope of the Gaoudan block, which is without difficulty reached from Anau, 6 miles east of Askhabad. The faulted face of this block, as seen from the Meshed road, is a precipitous escarpment of naked rock. The back slope, on the contrary, is a long, smooth descent, covered with soil, and closely corresponding to the dip of the limestone strata. In this are cut five or six black gashes, the parallel gorges of young consequent streams which have cut so deeply into the uplifted mountain mass that their sides appear from a distance to be perpendicular. East of Dushak, where the railroad leaves the base of the mountains, the strata of Kopet Dagh become softer and are more thoroughly dissected, but the hilltops still retain a flat aspect and the valleys are steep-sided and narrow.
. On the southern side of the mountains there is clearer evidence of recent
uplift. Looking northward from Meshed toward Kopet Dagh, the plain is bounded by a line of steep bluffs, which rise a thousand feet in one or two great jumps, and continue northwestward scores of miles. They are cut in strata, apparently Cretaceous limestone, which lie nearly horizontal, with a slight roll from northwest to southeast. The steepness and straightness of the mountain front, its slight dissection, and the absence of a stream competent to produce such effects suggest that the escarpment is the result of recent faulting by which the mountains were uplifted and subjected to renewed dissection. Between the top of the bluffs and the remarkably smooth crest of the range the uplands are rounded and mature in form. These same features continue far to the northwest, but in the neighborhood of Kuchan the bluffs decrease in height and the escarpment comes to an end. Apparently the fault gradually decreases in amplitude, and near Kuchan, after a course of about a hundred miles, is transformed into a simple flexure where the strata of the mountains dip southwestward and pass under the plain. In the neighborhood of the flexure the aspect of the mountains is more mature than in the regions which have been uplifted by faulting. This great displacement along the southern border of the mountains is parallel to the smaller displacements on the north side near Askhabad and seems to be of about the saine age.
The youthful character of the valleys in the uplifted block of Kopet Dagh agrees with the steep fault face in indicating that the uplift is of very recent date. For instance, in the mountains north and northwest of Meshed, Curzon (I, pp. 122, 123, 141) describes frequent instances of magnificent gorges from 1,000 to 1,50o feet