26 BULLETIN 54, U. S. DEPARTMENT OF AGRICULTURE. 
THE ALKALI LAKE BASIN. 
The Alkali Lake Basin is essentially a northward extension of the Abert Lake 
trough and is separated therefrom by the region of local cross uplift in the vicinity of 
Euchre Butte. On the east the basin is bordered, like Abert, by the scarp of an east- 
ward dipping monocline which merges toward the north into the less simple uplifts 
of Little Juniper and Wagontire Mountains. To the west the basin is separated from 
the Christmas Lake and Summer Lake Valleys by the usual inconspicuous divide 
across the lava plateau. It appears that the lake once received from this direction a 
main tributary which drained the pans and valleys of the lava plateau north of Sheep 
Rock. This drainage line has now been cut off almost entirely, and the lava plateau 
has been divided into numerous local basins. 
The deepest depression of the valley is Alkali Lake, a playa lake of very variable 
size. In the dry season it is usually reduced to three or four saline ponds occupying 
wind-eroded depressions in the playa. (Pl. III, fig. 2.) The northern extension of 
the Alkali Lake Valley, called ‘‘ North Alkali,’’ is now cut off from the main valley 
by a dam of wave and dune sand and has become somewhat saline. However, this 
separation is quite recent and does not affect the unity of the valley. A series of 
terraces about both North and South Alkali Valleys indicates previous occupation by 
a considerable lake, and, as all divides are far above these terraces, the lake must 
always have been inclosed. The drainage area of the lake was about 400 square 
miles, which has been reduced to perhaps a third of this value by the cutting off 
of North Alkali and of the pans of the plateau. 
THE WARNER BASIN. 
Mention has already been made of the eastward-dipping monocline the limiting 
scarp of which forms the eastern boundary of the Abert Lake Basin. This monocline 
is limited on the east by the scarp of a second monocline of precisely similar nature, 
and between the two scarps lies the Warner Valley. As usual, the deepest depression 
lies immediately under the scarp, being accentuated in this case by a minor parallel 
faulting to the west of the axis of the depression. The depression is a long narrow 
valley between a high steep scarp to the east, and to the west a much lower scarp 
from the crest of which rises the gentle monoclinal slope before mentioned. To the 
north and northwest the valley rises into a rolling plateau like those already described, 
and across which passes the inconspicuous divide between it and the Harney Basin. 
At the south the basin is limited by a zone of cross uplift and irregular faulting, 
beyond which lies the Surprise Valley. 
The Warner Valley is entirely surrounded by high divides and seems to have been 
always so inclosed. The surrounding mountains are furrowed by a series of lake 
terraces of usual character, the highest of which is (by aneroid) a little over 200 feet 
above the present lake. Several streams descend the gentle slope of the westward 
monocline and reach the valley proper through narrow canyons cut in the basalt of 
the low western scarp. During the lake period nearly all of these streams built 
typical deltas, the remnants of which may still be seen. (PI. IV, fig. 1.) 
The present floor of the valley is a flat clay plain, probably once a playa, but now 
diversified by considerable vegetation and by occasional dune areas or wind-scoured 
hollows. Shallow depressions hold two main lakes and several smaller ones, the 
whole being known as the Warner Lakes. All of the lakes are either fresh or merely 
brackish, but at the southeast corner of the northern or Upper Lake is a small pond 
containing a nearly saturated solution of sodium chloride. Its salt is believed to be 
derived from seepage. The separation of the Warner Lakes is very recent. They 
are still variable in size and are reported to have been considerably larger about forty 
years ago. 
