PLEISTOCENE SUBMERGENCE IN COLUMBIA VALLEY 495 



the east side of the range, are clear evidence of open waters through 

 the Gorge at the time of the submergence. Further, a study 

 of the various tributary valleys along the Gorge shows that local 

 glaciers, instead of filling it to a depth of more than a thousand feet, 

 probably never reached the Columbia. In Hood River Valley 

 there are moraine deposits apparently recording two different 

 glaciations, during the earlier of which the ice reached within 

 3 miles of the Columbia, and during the later not nearer than 

 5 miles. No other local glacier got as near as this to the Columbia. 

 It seems impossible that Hood River Glacier could have filled the 

 Columbia Valley to a depth exceeding a thousand feet and left no 

 trace other than these minor deposits back in the tributary valley. 

 Both Condon^ and LeConte^ have referred to glacial deposits near 

 The Dalles, but the writer has never seen anything in this region 

 which could be so interpreted. Topographic situations, altitudes, 

 and the location on the lee side of a mountain range all contribute 

 to weaken the h3^othesis of glaciation at or near The Dalles. The 

 Yakima Glacier, on the east slope of the range, 100 miles farther 

 north, did not descend below 2,000 feet A.T., though it was fed 

 from mountains much loftier than those near The Dalles. 



NEW EVIDENCE ESTABLISHING THE FACT AND EXTENT OF THE 



SUBMERGENCE 



Foreign bowlders and debris. — This can best take the form of a 

 Kst of occurrences and altitudes of foreign materials along the 

 Columbia and in some of its tributary valleys. 



Kelso, Wash. (5 mi. west of). Granite bowlder, 2I ft. in maximum diame- 

 ter. 50 ft. A.T. Has a pegmatite dike in it. Dike projects \ in. above the 

 pitted surface of the granite. 



Manor, Wash. (8 mi. north of Vancouver, Wash.). Granite bowlder in 

 schoolyard; angular, with fresh surface. Altitude close to 300 ft. A.T. 



Camas, Wash. Granite bowlder formerly on terrace back of the town, 

 at an altitude of about 175 ft. A.T. Has been broken up and used for founda- 

 tions. A fragment of it was examined. 



Willamette, Ore. (4 mi. southwest of). Several granite and quartzite 

 bowlders lying at the western foot of Pete's Mountain at 300 ft. A.T. Very 

 sHghtly weathered. 



'Thomas Condon, The Two Islands (Portland, 1902). 



= Joseph LeConte, "Age of the Cascade Mountains," Amer. Jour. Sci., VII 

 (1874), 167. 



J 



