138 B. WILLIS—DRIFT PHENOMENA OF PUGET SOUND. 
aid in determining the positions of the ice-tongues at various stages. Defi- 
nitely marked terminal moraines across the front of the glacier at any 
stage have not been observed. 
The northwestern portion of the plateau which lies between Cedar 
river and Green river is marked by a zone of Vashon drift which pre- 
sents a marginal aspect. On the southeast the zone is bounded by the 
washed plains of the former course of Cedar river through the Wilder- 
ness. Beyond these plains eastward is the local drift of the Cascade 
glacier. The Vashon ice and the Cascade ice met along the Wilder- 
ness. In many places a steep slope rising along their northwestern side 
defines the limit between the washed gravels and the gravelly loams of 
the Vashon marginal zone. The latter is about 3 miles (5 kilometers) 
wide from southeast to northwest. It includes many lakes, of which 
Swan lake is the largest. The relief within the zone is 100 feet (80 me- 
ters) or more in height, not including the deeper pre-Vashon hollow oc- 
cupied by Big Soos creek. The forms are, however, broad and lack defi- 
nition. Summits, slopes, and hollows merge obscurely. Nothing is 
clearly cut in profile. Broad ridges of coarse material merge longitudi- 
nally into mammillated surfaces which pass into smoother plains of 
typical till. Between the ridges hollows of irregular depths and con- 
tours are floored with sands or loam, and now contain muck-swamps. 
The ridges trend from west of north to east of south in a general way 
parallel to Big Soos hollow. This trend is at right angles to that which 
would be assumed by a terminal moraine, such as might have formed 
had the glacier ended with a free front. 
The marginal zone of the Vashon ice is interrupted between Green 
and White rivers. . Drift is probably buried beneath alluvium in their 
valleys. The narrow plateau between them is washed as are the plains 
along the Wilderness, presumably by the same streams, but on the pla- 
teau between White and Stuck rivers the Vashon drift exhibits strongly 
marked marginal characteristics. Among bold ridges which trend south- 
eastward lies lake Tapps, typically fingered. The southeastern margin 
of the Vashon drift here runs out upon the plains of Osceola till, on 
which extend the swamps drained by Fennel creek. Southward the 
zone extends along the western edge of the plateau in a belt about 3 
miles (5 kilometers) wide, over the hill above Orting, whose summit is 
900 feet (274 meters) above sealevel, and thence spreads southeastward 
to Carbonado and Wilkeson. In this southeastern district the Vashon 
ice impinged against glaciers from mount Rainier and its foothills. The 
arrangement of the spurs coming down to Wilkeson prevented the Rainier 
glaciers from ‘flowing out directly against the Vashon ice, and thus it was 
a 
