THE NORTHERN PACIFIC ROUTE. 177 
All the lava folds crossed so far in the Yakima Valley are either 
steepest on the north side or overturned, like that of Atanum Ridge 
at Union Gap. This overturning toward the north indicates that 
when the folds were produced the thrust came from the south, and it 
continued not only until the beds were arched but until the arch was 
pushed over, so that the beds on the north side stand nearly vertical 
or dip steeply toward the south. The northern limit of this fold is 
marked by the valley of Umptanum Creek (see sheet 26, p. 186), 
which enters the river near milepost 114. 
North of Umptanum Creek lies Manastash Ridge, which, like the 
others already crossed, is an arch in structure; but the fold is much 
flatter than those down the river, and its shape is not apparent from 
the train. The layers of basalt rise gradually northward from the 
mouth of Umptanum Creek, and they appear to be nearly horizontal 
in the great Beavertail Bend between mileposts 115 and 118. The 
axis of the fold is more than a mile north of this bend and not far 
from milepost 120, where the railway again crosses to the east side 
of Yakima River. From this crossing the layers of rock descend 
rapidly northward, and the great sheets of basalt that form the walls 
of the canyon for more than 20 miles dip below water level and the 
train emerges upon another broad flat that seems to be even more 
extensive than the one at North Yakima. This also is mostly under 
cultivation, and the view on the right as the train leaves the canyon 
is particularly charming, as one looks off to the distant mountains 
across a wide stretch of fertile fields and orchards, crossed here and 
there by lines of tall trees planted as windbreaks. 
Although much hard rock is exposed in the Yakima Valley stone 
suitable for building material is very scarce. The basalt is a lasting 
material, but its dark color renders it unsuitable for 
— buildings and it is used only for foundations and 
Bt Para eae teet- for road metal. For the latter use it is admirably 
adapted. On the north slope of Manastash Ridge, 
about 2 miles east of Thrall, the sandstone of the Ellensburg forma- 
tion has been hardened by the pressure that arched and overturned 
the basalt so as to make it a very good building stone, and it has 
been utilized in some of the business blocks of Ellensburg. 
Ellensburg is the end of a division and a prosperous town in the 
broad Kittitas Valley, which stretches far to the 
Ellensburg. east along Manastash Ridge. It is served not only 
Elevation 1,518 feet. by the Northern Pacific but also by the Chicago, 
Fico rele al Milwaukee & St. Paul Railway, which gives it an 
advantage over most of the other towns of the 
Yakima Valley. Owing to the altitude, the land is much better 
95558°—Bull. 611—15——12 | 
