TOPOGRAPHIC FEATURES OF THE DESERT BASINS. 29 
THE LONG VALLEY BASIN. 
Long Valley lies just east of the Surprise Valley, beyond the crest of the gentle 
anticline (?) already mentioned. It is a poorly defined valley the detailed structure 
of which is very complex. On all sides it merges with the folded and dissected 
lava plateau already mentioned. Its floor is an irregularly shaped playa dotted 
with shallow and variable lakes, between which are very low and inconspicuous 
divides. Several low passes lead out of the valley at about the same elevation, one to 
the Coleman Valley (a tributary of the Warner Basin) and the others either to Duck 
Flat or directly to the Surprise Valley. Without detailed examination it is not pos- 
sible to determine which of these, if any, was a channel of ancient discharge. The 
writer inclines to the opinion that during the Lahontan period there was free or over- 
flow discharge into Duck Flat and thence to the Surprise Valley, but this conclusion 
can not be considered certain. The present lakes are fresh or brackish only. It is 
not possible to determine the present drainage of each. The area of the whole valley 
is about 775 square miles. 
. 
THE ALVORD VALLEY. 
It will be recalled that the shallow syncline of the Catlow and Guano Valleys was 
bordered on the east by the uplift of the Steens Mountains. The eastern face of this 
range is a high fault scarp, directly below which hes the Alvord Valley. Like the 
Warner and Abert Valleys it is essentially monoclinal in structure, though an anti- 
clinical structure previous and parallel to the faulting has been detected by both 
Russell and Waring. In the Steens Mountains this anticlinal structure seems to be 
entirely overshadowed by the much more profound monoclinal movement, but east- 
ward from the Alvord Valley faulting and tilting have not been so profound and the 
eastward divide of the basin seems to be determined by the crest of one of the original 
anticlines. To the south the basin reaches the less regular uplifts of the Pine Forest 
Mountains and Trident Peak. It is separated from the Black Rock Desert only by 
an alluvial divide across the Pueblo Valley, but this divide is nearly a thousand feet 
above the valley and is almost certainly pre-Lahontan. The northern extremity of 
the Alvord Valley is little known and it is possible that there may have been an outlet 
to the Malheur River, though the considerable salinity of the valley and the presence 
of old strand lines around it would indicate the contrary. 
The present bottom of the valley is cut by alluvial divides into the subsidiary basins 
of Ten Cent, Juniper, Mann, Alvord, and Tum Tum Lakes and that of the Alvord 
Desert. All of these were covered and connected by the early lake and it is possible 
that most of the others drained into that of the Alvord Desert for some time after 
desiccation had begun. The White Horse Basin was also a former tributary and has 
been cut off by the accumulation of alluvium and dune sand in Sand Gap, through 
which it formerly discharged. 
The Thousand Creek and Virgin Creek Valley ae on the lava plateau east of 
Long Valley, Nevada, seems to have been also a tributary of the Alvord and is now 
separated thereform only by a low alluvial divide in the gap north of the Pine Forest 
Mountains. This valley has suffered greatly by stream decay and now contains 
numerous local playas of small area and very recent origin. 
The areas of the various small basins into which the Alvord Valley is now divided 
have not been computed in detail. Their total area, exclusive of the White Horse 
Basin and the Thousand Creek Valley is about 1,600 square miles. The area of the 
White Horse Basin is about 300 square miles, and that of the Thousand Creek Valley 
1,300 square miles, making a total of 3,200 square miles for the drainage area of the 
Alvord Basin during the Lahontan period. 
