272 THE BASIN OF EASTERN PERSIA AND SISTAN. 
tributaries of the Yeshil Irinak or Iris, and along the steep mountain torrent which 
flows from the lofty Pontic range northward to the Black Sea at Tre1)izond. These 
phenomena are probably due to the same cause as the similar phenomena farther 
east in Persia and Turkestan. 
TERRACES IN NORTH AMERICA. 
The southwestern part of the United States is not unlike large portions of 
Central Asia, and among its higher mountains we should naturally look for gravel 
terraces if our conclusions concerning climatic changes are correct. As a suggestion 
of the sort of phenomena to be looked for, I shall cite a few examples which I saw 
in Utah and Arizona during the summer of 1902. 
The first example is the Kanab Canyon, in Southern Utah, which has been 
described by Professor Davis {b, pp. lo-ii). This steep-sided young canyon con- 
tains "two terraces of well-stratified alluvium, usually of fine texture and containing 
lateral unconfonnities such as are to be expected in the deposits of aggrading streams. 
The higher terrace is 80 or 100 feet over the stream-bed. It is less continuous than 
the lower one, which stands from 40 to 75 feet over the stream. The channel below 
the lower terrace is the work of a series of floods, beginning in the summer of 1883. 
A great part of the alluvium then accumulated along the valley was swept rapidly 
away." In external appearance and scale these terraces are like many of those found 
in Persia and Turkestan, and the character of the surrounding mountains is the same 
in both parts of the world. The sudden sweeping away of the alluvium from the 
canyon and the formation of the lower terrace in the course of a few years may be 
compared with similar action taking place in Asia. At Naumzabad, a few miles 
south of Serakhs on the Heri Rud (Tejan River), my guide pointed out a place 
where, during the great flood of the preceding spring, whose appearance at Tejan 
has iDeeii described b)' Professor Davis, a mass of alluvium half a mile long and 
nearly a thousand feet wide was washed away, leaving a bluff a hundred feet high. 
Among the mountains of Persia it frequently happens that if a terraced valley be 
followed toward its head, points will be found where the terraces, one after another, 
come to an end. Often this ending, especially in the case of the lowest terrace, is 
very sudden, and it is manifest that in ever}- great flood the inner channel cuts head- 
ward and the terraces are prolonged upstream. 
A less marked, though distinct, example of the same process of valley-filling 
and terracing is found along Le Verkin Creek, near Toquerville, 50 miles west of 
Kanab. The bottom of the young valley of the creek is filled with from 10 to 20 
feet of alluvial gravel, which the stream has now dissected, fonning a rude terrace. 
These few examples of terraces in Turkey and North America are not supposed 
to lead to any definite conclusion, but are presented merely with the purpose of 
showing that if our conclusions as to the terraces of Central Asia are correct, these 
features in other lands are what we should expect. Prolonged study is necessary 
before we can correlate facts so widely separated. The glacial period was a world- 
wide phenomenon, and to understand it fully we must take a world-wide view. 
