E. Blachiv elder — Takutat Coastal Plain of Alaska. 461 



warm Pacific ocean and keep the mountains enveloped in 

 nimbus clouds for days at a time, with only occasional sunny 

 intervals. Showers and fogs are of frequent occurrence. The 

 climate in summer has, therefore, been aptly characterized as 

 " damp and chilly." In winter the snowfall is heavy, but the 

 freezing of both soil and streams checks the operation of the 

 processes we have to consider. 



Under the influence of this climate a dense growth of boreal 

 vegetation covers the plain. On the flat nndrained parts, 

 grassy marshes and willow swamps prevail. On moraines, 

 sandy ridges, and, in fact, wherever the soil is subject to drain- 

 age, there are dense spruce forests with a clank undergrowth of 

 mosses, ferns and u devils-club.' 1 Everything there is soggy, 

 even on the drier days. 



Needless to say the rivers are permanent and brimming, 

 although subject to fluctuations according as the rains are 

 heavy or light. All but the Alsek are short streams, but some 

 even of these rise in the abundant glaciers which choke the 

 mountain valleys. The glacial rivers are swift, and are milky 

 with fine sediment; but the others, which draw their water 

 through many swamps and lakes, are clear. In the history of 

 the plain the glacial ■ streams are probably of far more import- 

 ance than the others. The rivers which cross the plain are 

 engaged in aggrading. They have no valleys, and their 

 immediate channels are sunk but a few feet beneath the plain.* 



Having this picture of the district and its conditions, we 

 may now consider the structure and composition of the plain 

 itself. The foreland is composed entirely of unconsolidated 

 Quaternary sediments. Near Yakutat Bay, and subordinately 

 elsewhere, low glacial moraines make the surface The rest of 

 the material was deposited by water or wind, and is stratified. 



The plain seems to have been built out into the ocean by 

 shifting aggrading rivers. These rivers are swiftest near the 

 mountains and become slack at tide-level. On this account 

 the sediments are graded in coarseness. Near the mountains, 

 coarse gravel predominates ; but as one passes seaward he may 

 trace the gravel into sand and finally into silt. This zonal 

 arrangement of gravel, sand and silt probably persists roughly 

 with depth, for the conditions of gradient have doubtless been 

 similar through much of the history of the plain. 



In composition the sediments have certain distinctive fea- 

 tures. The colors are limited to black and grays of various 

 intensities. Tinges of green are not uncommon but are faint. 

 ^Yhen examined closely the sediments are found to consist of 



* The work of these streams as seen in front of the Malaspina glacier has 

 recently been described by Tarr, Zeitschrift fur Gletscherkimde, iii, 88-93. 



