PHYSIOGRAPHY OF THE BEAVERDELL MAP-AREA. 
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Terraces. 
The floor of a broad U-shaped valley like the West Fork 
is made up of a series of terraces becoming successively higher 
as one moves from stream trench to valley side. In valleys of 
the canyon type, they are often found in remnants above the 
steep V of the canyon. Typical upland draws which have no 
canyon trenches in their floors do not show terraces. Figure 
3 is a cross section of the West Fork above China creek showing 
the terraced floor. 
In following a particular terrace up or down the valley, one 
finds it occupying the greater part of the floor in one place and 
in another existing only as a narrow ledge upon the side hill or 
as an isolated flat topped remnant within the valley bottom, while 
there the major part of the floor is taken up by a higher or lower 
member of the terrace series. Fragments of terraces sometimes 
exist several hundred feet above the valley. The terraced 
character of these large valleys is obscured in places by alluvial 
fans, kettle holes, dry channels, and outcrops of bedrock, but 
it is the dominant feature of the bottoms of the larger valleys. 
pAKES AND SWAMPS. 
A number of small lakes are scattered through the upland 
country, most of them being found in the northeastern parts of 
the quadrangle, and one or two occur on the floors of the deeper 
valleys. The largest one, Joan lake, does not cover more than 
about 200 acres, the smallest ones are mere ponds. They vary 
in depth but are probably for the most part shallow. The upper 
of the three Arlington lakes in the valley of Hall creek measured 
24 feet at its deepest point. Some of them occupy rock basins, 
as in the case of Joan and Cup lakes, others seem to be merely 
dammed up by loose debris assisted by the work of beavers. In 
some cases the lake is a sheet of water in the middle of a swamp, 
but a number of them have rocky or sandy shores and clear 
water, and when surrounded by an unbumt forest, as is the 
case with Clark and Joan lakes, are very picturesque. 
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