TERMINAL MORAINE OF TV GET SOUND GLACIER 167 



and below a low pass across the divide to the Des Chutes River, 

 was Puget Sound glacial gravel found in the Skookum Chuck 

 v valley. 



Clear Lake, at Mcintosh station, 4 miles east of Tenino, lies 

 in a marginal drainage channel discharging westward into the 

 outwash gravel area at Tenino. The terminal moraine lies imme- 

 diately north of this lake. North of Tenino, the moraine is of a 

 character considerably changed from that in the Bald Hill region. 

 It has here become a single massive till ridge on the plain, and sur- 

 face bowlders are not sufficiently numerous to attract attention. 

 It is two miles wide and 250 feet above its base on both north and 

 south sides, the highest point examined reaching 550 feet A.T. 

 On each side, it is flanked by an outwash gravel plain bearing 

 peculiar tumuli. The till mass appears to cover several rock knobs 

 and hills, whose existence may have in some measure determined 

 its location and relief. Both east and west of Tenino, quarries 

 in sandstone have been opened on the slopes which rise farther to 

 the north in the moraine. The road north from Tenino to Olympia 

 cuts into decayed shale strata in situ at the summit of its grade 

 across the moraine at about one-half the maximum height of the 

 moraine, and at Mcintosh rock outcrops occur on the south base 

 of the moraine. 



The hills which rise south of Tenino were carefully examined 

 for drift materials. Three distinct terraces of outwash gravel were 

 found, occasionally showing forests beds descending southward 

 toward the Skookum Chuck. The highest gravel lies 360 feet A.T., 

 and above it drift abruptly ceases. 



Flanking the frontal margin of the moraine from Tenino west 

 to Black River is an extensive area of outwash gravel, known as the 

 Grand Mound Prairie. It is entirely barren of forest growth 

 and almost useless for any agricultural purpose because of the 

 coarseness and depth of the gravel. At the contact between 

 moraine and outwash examined no apron structure was found. 

 The gravel plain apparently was built by outwash occurring through 

 breaks in the moraine ridge and not by outflow from the ice edge 

 when standing at its maximum limit. 



The whole region south of Puget Sound bears much outwash, both 



