LATERAL MORAINES. MOT 
On the western side of the Duwamish valley, 3 miles (4.8 kilometers) 
north of Kent, the slope which rises from the alluvial plain curves south- 
westward from a projecting promontory. Within this curve the slope 
is 350 feet (100 meters) in height, and is diversified by a group of pecu- 
liar ridges. The ridges lie upon the slope and trend south at an angle 
to the direction of steepest descent. They occur in groups of two or 
more, which are roughly parallel, but which coalesce at points along 
their course, forming enclosed kettles. They are 40 feet (12 meters) 
or more in height and from three to five times as long as they are wide. 
Their southeastern slope is steeper than the northwestern, and their 
crests descend from the point of contact with the hill above toward the 
south. They are composed of clayey gravel, sometimes heterogeneously 
mixed and again stratified. Large boulders may be seen, but do not 
form a prominent feature. The distribution of these small ridges ex- 
tends from the point of the promontory on the north along the convex 
side of the embayment for a distance of 8 miles (5 kilometers) to a point 
nearly west of Kent. ‘The ridges are homologous in form, position, and 
material to certain lateral moraines, which can be seen on mount Rainier 
in their true relation to the Carbon River glacier at the present time. 
They constitute a record of the lateral shrinking of that tongue of the 
Vashon glacier which followed the Duwamish valley and still occupied 
the space between the plateaus in the latest stages of its retreat. These 
ridges are older than the alluvium beneath which they disappear. 
At a point 16 miles (25 kilometers) south of the above-described lo- 
eality, on the eastern side of the Puyallup valley, the escarpment of the 
plateau presents features of glacial construction. At an elevation of 
400 feet (120 meters) above the valley a ridge one-quarter of a mile (400 
meters) in length extends from point to point of the plateau slope, en- 
closing between it and the plateau several hollows. The ridge is so 
narrow and even as to resemble a huge embankment. The kettles be- 
hind it are 60 to 100 feet (20 to 30 meters) in depth and of unusual size. 
Atits southern end the ridge constitutes a promontory, with a very steep 
southern slope. In a section exposed by a road grade on this declivity 
the relation of the ridge to the plateau mass can be seen in section. The 
ridge is composed of coarse and fine gravel and sand, with large boul- 
ders. The mass of the plateau at the level at which the section is ex- 
posed consists of fine sands, which are horizontally stratified and are 
recognizable as one of the older Pleistocene formations traced through- 
out the Puyallup valley. The contact plane between the moraine mate- 
rial and the sands dips 60° to the west toward the valley. It is undis- 
turbed, and clearly a plane of deposition and not a landslide fault plane. 
The relation of this ridge to the plateau mass is thus seen to be indicated 
XIX—Burt. Gro. Soc, Am., Vou. 9, 1897 
