SHASTA EOUTE SEATTLE TO SAI:^ FRANCISCO. 



29 



Columb 



mile 



Columbia River to 

 Portland. 



length and 30 to 100 feet deep. (See fig. 4.) This 

 cut goes through part of a terrace that projects 

 into the angle between Columbia and Willamette 



rivers. East Portland is built on this terrace. Tlio principal 

 laterial exposed in the cut is fine sand, rudely stratified and con- 



taining scattered 



Buff loarn^4-6feet 



Cross-bedded sand 



and gravel, 40 feet 



lenses and streaks 

 of gravel, with a 



s 



as 



Fine sand with few 

 pebbles and streaks 

 of clay, 60 feet 



FiGiTRE 4.— Section of deep cut of Northern Pacific Kailway across Portland 



Peninsnla between Vanconver. Wash., and Portland, Oreg. 



few pebble 

 much as 6 inches 

 in diameter. In 

 this material at 



intervals of 3 or 



4 feet there are thin beds of clay or clay and sand. Above this lies 



coarse cross-bedded gray sand and gravel capped by buff loam. 



Beyond the cut the railway crosses the Willamette at "Willbridge 

 and turns to the left up that stream. East of the river, above a 



University (Cathohc). In the bluff, which is 175 



Columbia 



feet high^ are exposed lower beds than those seen in the cut, and they 

 include^ as may be seen at one point southeast of Mocks Bottom, 

 larger bowlders and coarse gravel. On the right as Portland is 

 approached is Guild Lake, the site of the Lewis and Clark Exposi- 

 tion in 1905. It is now being filled for factory sites by washing in 



^ 



imq' The Heights of Portland 



Sea level 



§ 



PorQajid 



■tlarid 



^ 

 $ 



Mt Tabor 

 d 



.■.■■.v.-.-.-i-:. 







L 



'/I 



I 





V700 



and, gravel, and bowlders of Quaternar^^ age 



t 



Alternating layers of compact marl. shale, 

 fossil p)an\5,i.enite,sand.andgrayel, sup- 



Jl posed w be of Tertiary age 



^ "Granite" 



Figure 5.— East-west section of Wfflamette VaUey at Portland, Oreg. , sho-^-ing the relations of the sandy 

 loam (a) and the basalt (b) of Portland Heights to the sand and gravel (c) on which Portland and East 

 Portland are built and to the gravel ((i) of Mount Tabor and the sandy loam {e) best exposed on the 

 upper slopes of Westover Terrace. 



gravel. Across tlie lake is a dark bluff, which is notched b j the ravines 

 of small streams that drain a plateau west of it. The bluff, which 

 is made up of basalt lava, is capped by buff sandy loam that has 

 resulted from the weathering of the basalt. A diagrammatic section 

 from the plateau on the west, through the river terraces on which 

 the cities of Portland and East Portland are built, to Mount Tabor 

 on the east is shown in figure 5. 



The flat-topped heights west of Portland, including Council Crest, 

 are part of what in early Pleistocene time was an extensive nearly 

 level surface produced by erosion — a peneplain, as it is termed by 



