TERRACES IN TURKEY. ZJl 
extended to that country, and if those changes are competent to produce recognizable 
physiographic forms. The cause of the abundant terraces of Western Asia demands 
much further investigation, but it is at least a fair working hypothesis that the 
terraces are due to a series of climatic oscillations, and that those oscillations were 
contemporaneous with the successive epochs which in other lands composed the 
glacial period. If this theory proves worthy of acceptation it will probably furnish 
the necessary clue to the elucidation of the recent physical histor)- of the Caspian 
basin and of other parts of the earth's surface immediately before and perhaps after 
the advent of man. 
TERRACES IN TURKEY. 
If the conclusions which have been reached in the preceding pages of this 
report are correct, terraces of climatic origin ought to jircserve a record of some of 
the epochs of the glacial period in other parts of the world, especially where the 
conditions resemble those of Persia, that is, among unglaciated mountains in the 
stages ot youth and early maturity in regions of slight precipitation. Several j-ears 
ago, in Eastern Turkey, a thousand miles west of the part of Persia which we have 
been considering, I ob.served numerous terraces which I could not then satisfactorily 
explain. Almost invariably the bottoms of the valleys of Eastern Turkey are filled 
with gravel in which the streams have incised newer valleys, often to a considerable 
depth. Thus along the Euphrates River in its upper course, where it flows west- 
ward before turning southward and eastward on its long course through Mesopotamia, 
there is a strong gravel terrace almost everywhere except in the narrow canyons. In 
the Malatia plain, for instance, this terrace ranges from 30 to 60 feet in height. 
Farther upstream, along the eastern branch, or Murad Su, a few miles east of Pertag, 
there is a half-consolidated gravel which evidently was deposited in the valley after 
it had attained nearly its present fonn, and there are also two terraces, one about 50 
feet high and the other nearl)' 100. In the small tributary valleys of Pekanik and 
Kurdemlik, which here descend steeply northward from the Harput Mountains, 
there is a dissected valley deposit of alluvium which reaches a thickness of 100 feet. 
The deposit is for the most part composed of silt and very fine gravel, quite different 
from the cobbles and coarse gravel which now fill the stream-bed. In these deposits 
and in many others there are marked imconfonnities like those of Bajistan, where 
relatively coarse material suddenly succeeds fine silt. Still farther up the Euphrates, 
and along some of its main branches, as for instance, in the Harput and Peri plains, 
there are extensive gravel deposits in which the streams have deeply intrenched 
themselves. As the higher mountains of Dersim are approached along the Peri 
and Muzur rivers the terraces become more distinct. In my notes on a number of 
the smaller streams there are references to "alluvial terraces," "terraced valleys," 
"a series of terraces," or "several terraces," most if not all of which are cut in 
gravel. The number of terraces is not stated, for their possible significance was not 
then appreciated, and most of them are small features, easy to overlook. 
Terraces are found in other parts of Turkey in addition to the Euphrates Valley. 
My notes contain references to similar phenomena along the Tigris in its upper 
course southeast of Gyuljuk, along the Kizil Imiak or ancient Halys, along the 
