242 THE BASIN OF EASTERN PERSIA AND SISTAN. 
The remainder of the Afghan depression may be smnmed up briefl>-. In the 
southwestern corner of Afjjhanistan lies the hollow of Sistan, bounded to the west 
by the unknown, and probably unknowable, escarpment of Palan Kuh (Panther 
Mountain). Then comes the God-i-Zirrah in Baluchistan, a part of the Sistan 
hollow; and lastly, to the southeast, the hollow of Mashkel, west of which, near 
the edge of the escarpment, lies the active volcano of Kuh-i-Taftan. From north 
to south the Afghan depression, varietl as it is in character, forms a continuous whole. 
So, too, from the Jam basin southward, does the escarpment which foniis the western 
edge and dixides the basin of Sistan from that of Persia. It is not by accident that 
the boundary between Afghanistan and Persia is located along this line. The Heri 
Rud, so long as it flows in a gorge, forms an unmistakaljle frontier which can not 
easily be crossed. The deserts of Nemeksar and the Desert of Despair form an 
even more effectual barrier. In two places the frontier is weak. One is where the 
Heri Rud turns northward and the plains of Jam and Herat coalesce. At this 
point there is no natural barrier, although the land southwest of the bend of the 
river is so nearly desert and of so little value that it affords small provocation for 
quarrels. The other weakness is at Si.stan, where the boundar)' arbitrarily bends 
eastward to the Helmund River, leaving the incomparable natural boundary- afforded 
by the absolute desert at the base of Palan Kuh. Geographically, the whole of 
Sistan belongs to Afghanistan. Until the political boundary coincides with the 
natural boundary it is not to be expected that Persia and Afghanistan can avoid 
quarrels. 
THE TERTIARY HISTORY OF THE BASINS OF EASTERN PERSIA. 
In a preceding paragraph an outline has been given of the histoiy of one of 
the minor basins of northeastern Persia. 
The Zorabad Basin. — Apparently the Zorabad basin was first occupied by the sea 
and later became dr)' land. Then, by the warping of the earth's cni.st, it was con- 
verted into a lake, which in time was drained by the cutting of a gorge. As the 
water of the lake receded gravel was washed in from the sides and covered the lake 
deposits. Since that time the gorge at the outlet has been cut deeper, the \'arious 
deposits have all been more or less dissected, and terraces have been formed. At 
inter\'als during the progress of these events warping has gone on in such a fashion 
that the size of the basin has continually diminished and all the deposits except the 
most recent gravels have been warped along the edges, although apparently remain- 
ing horizontal in the center of the basin. Most of this histoiy probably belongs 
to Tertiary times, although the dissection of the lake deposits and the formation of 
the terraces almost certainly belong to the present geological era. 
In order to understand the geological history- of Persia it will be necessary to 
ascertain to what extent a similar series of events has occurred in other basins. 
What few facts are known indicate that the history of all the basins is similar to 
that of Zorabad, with the exception of the lake episode. The only lakes of which 
we have record in the other basins occurred at a later time and were due to changes 
of climate rather than to warping of the crust. 
