26 



GUIDEBOOK 



•iintry from Piiget Sound to the Gulf of Ciili 

 5 since followed by the Southern Pacific Co. 



tinent 



Columbia ^ is the great waterway from the int 



In 1805 it bore the 



transcontuient al 



Columbia River. 



from 



to the sea. Their party spent 



winter 



the 



Pacific coast ai 



Columbia Eiver, including its tributaries, has a drainage area of 

 about 259,000 square miles and a total navigable length of 2 136 



miles 



em as a whole is capable of furmslnnor an estim 



maximum 



horsepower, less than 2 per cent, was developed in 1909, the latest 



year for which 



com 



statistics are available. In five States, 



1 Columbia River from the lower cas- | very gradually sank and the ocean water 

 cades to its mouth, a distance of 140 miles, 

 IS, like the Hudson, a good example of 

 what eeoerraDhers term a^Mrownf^fl rlv*^r " 



The earth's surface is not absolutely stable 

 but is subject to upward and downward 

 movements. As a rule these are so slow 

 as to escape notice except in so far as their 

 effects can be seen and interpreted by 

 those who make a study of land forms. 

 ^\Tien a broad section of coast land trav- 

 ersed by a river moves downward, the sea 

 water advances into the depressed and 

 thereby deepened river channel, the 

 river water is backed up, perhaps for 

 many miles, and the lower part of the 

 river so affected becomes a narrow inlet 

 whose waters, Instead of gliding steadily 

 to the sea, ebb and flow with the tides. 



As was explained on i);ige24, the Colum- 

 bia in early Pleistocene time, many thou- 

 sands of years ago, flowed in a broad valley 

 whose floor is now represented by the flat 

 tops of the hills seen near Kalama. The 



land, which I)roba]^lvh^lf1 bAt^n Hfa+in^o^^r 



bega 



Tlie 



slope of the river chaimel was increased, 

 the water flowed faster, and, with the sand 

 and bowlders of its channel as abrasives, 

 the river began to wear down its bed. 

 This went on until the land stood higher 

 than at present and the river had cut its 

 bed to a very gentle grade. Then the 

 earth movement was reversed. Tlie land 



backed up into the Columbia. It was 

 this sinking that transformed the lower 

 Columbia into a navigable stream, deep 

 enough for ocean-going steamers, and 

 made possible the commercial develop- 

 ment of Portland and Vancouver. This is 

 merely one of many illustrations of the 

 direct bearing of past geologic events and 

 processes on modern life. Tlie influence 

 of some of those processes, such as the 

 formation of coal, is plain enough to all. 

 The influence of others, though equally 

 real, is not so obvious. 



The mean range of the tide at Lower 

 Cascades is only .0.2 foot, at Vancouver 0.8 

 foot, at Portland 1 foot, and at Astoria 6.4 

 feet. The fluctuation in the height of 

 the river due to changes in meteorologic 

 conditions is more than 20 feet at Port- 

 land and Vancouver, so that the tidal 

 oscillations there are of very slight prac- 

 tical importance. 



Rivers are the sculptors of their own 

 valleys. The wild gorge through which 

 the Columbia traverses the Cascade Ptange 

 (PL VII, p. 23) is the noblest of its kind 

 on this continent. Its history has not 

 been fully made out, but it appeal's that 

 the Cascade Range was slowly uplifted as 

 in the form of a series of broad arches or 

 uptilted blocks of the earth's crust along 

 a north-south axis, and that the river, 

 which is thought to have had nearly its 



