PACIFIC COAST, YAKUTAT TO ALSEK RIVER. 85 
Russell Fiord and extending eastward along the base of the range 
nearly as far as Anklin River. This moraine, with its hillocks and 
lakes, is believed to have been made by a glacier which formerly occu- 
pied Russell Fiord. The glaciers in the front range have left only 
small and relatively fresh moraines. At the foot of the Yakutat 
Glacier, the largest lobe of ice between Yakutat Bay and Alsek River, 
a broad, flat terminal moraine hems in a crescent-shaped lake, which 
in turn borders the present end of the glacier. This moraine has 
every appearance of being a comparatively recent deposit. 
Aside from the deposits of till there is a vast amount of stratified 
glacial drift mingled with the strictly ffuviatile sands and gravels of 
the coastal plain. 
This alluvium of double origin forms much the largest part of the 
foreland. 
RECENT ALLUVIUM. 
The streams coming down from the front range, including the 
Alsek itself, are engaged in building a plain of sand, gravel, and silt 
out into the Pacific. The formation of salient deltas is prevented 
by the strong littoral currents, which sweep the finer detritus along 
the coast and out of it build bars and spits in favorable situations. 
To some extent the wind has formed low sand dunes along the- coast, 
but the effectiveness of this process is reduced to a minimum by the 
dampness and the rapid growth of vegetation. 
STRUCTURE. 
The structure of the most ancient metamorphic series is not defin- 
itely known, but is confidently believed to be highly complex. 
Both of the younger bed-rock series are intensely and intricately 
folded. The folds are as a rule isoclinal and in many places over- 
turned toward the west. The strike of the folds is not everywhere 
parallel to the axis of the range, as it might be expected to be. Near 
the Yakutat Glacier it trends north-northwest, making an angle of 
40° to 50° with the general axis of the mountains. On this account 
the individual folds come out successively into the plain and dis- 
appear; but as the crumpling is repeated over and over again in about 
the same plane, no older or younger formations are exposed. The 
details of structure exhibited by the slaty rocks are in many places 
extremely complex, but the massive layers of graywacke are more 
regularly flexed. The structural relation between the Yakutat series 
and the schistose strata on the Alsek was not determined. The 
marked difference in metamorphism between the two series is thought 
to imply that they are separated by an unconformity; if not, then 
the schists of the Alsek may be merely a more altered eastward 
extension of the Yakutat slates and graywackes. 
