300 R. S. TARR AND LAWRENCE MARTIN 
sible to see more than a few rods, and to face it was positively 
out of the question.”” Upon the loess-covered surfaces there is, 
variably, (a) thick forest (Fig. 4), (b) sparse vegetation, (c) grassy 
slopes, and (d) bare soil. Near where the present transportation 
of the finer material by the wind can still be observed, the grass 
and trees are notably dusty and there are many dead trees, still 
standing erect. Doubtless the stumps in the loessian deposits 
represent trees killed by dust accumulating about their trunks. 
The preservation of this wood seems to be due to burial in the 
compact eolian deposit, perhaps in part to the frost, which may 
also have had something to do with the killing of the trees. The 
shortness of the stumps seems to come from the fact that the wind 
blew down the dead tree trunk after it was thoroughly dry, but 
before it was deeply buried in the loess soil. 
The conditions found in the Copper River basin favoring the 
transportation of dust by the wind and the deposition of eolian 
silt or loess are: (a) abundant water from glaciers, (6) much 
sediment, (c) anastomosing branches, (d) shrinkage of the streams 
in the fall and spring when winds are strongest, (e) a rather dry 
climate, and (f) dust storms. 
In comparison with other areas of similar accumulations the 
Copper River basin has loessian accumulations as (a) terrestrial 
deposits; (b) as in some cases (for example, the Mississippi Valley) 
associated with glaciation; (c) as in some, perhaps all, cases, thick- 
est along rivers; (d) coarser than that of the Mississippi Valley. 
This coarseness may be due to (1) the nearness of the rivers; (2) the 
violence of the winds here; (3) the coarser sediment carried in the 
steep-grade streams of Copper River basin as compared with the 
less steep grade of the Mississippi and its glacial tributaries. 
CONCLUSION 
The presence or absence of all these drift deposits seems to be 
chiefly a matter of favorable topography and drainage. The 
deposition of the loess or eolian silt seems to be directly related to 
the glacial outwash, to variations of river volume and water level, 
to the amount of rainfall, and to the winds. Existing deglaciation 
in the interior of Alaska is apparently a process much like that 
formerly in progress in northeastern and central United States. 
