CHAPTER XXXII 

 GILBERT'S LAST STUDY 



RETURN TO AN OLD THEME 



It appears from an earlier chapter that, in spite of the rich opportunity for further study 

 among the mountain ranges of the Great Basin, as shown by his own work on the House 

 Range and by Louderback's excellent paper on the Humboldt Ranges, Gilbert turned his 

 attention for a number of years to other matters, as if the calamity of 1901 had produced a 

 revulsion of feeling and given him a distaste for what had before so greatly attracted him; 

 and it is noteworthy that, as has already been pointed out, chief among other matters then 

 taken up was the quantitative investigation of the transportation of debris, to which he had 

 long before given a penetrating qualitative analysis in the third part of his Henry Mountains 

 report. It is now to be told that, on the completion of the debris investigation, he turned 

 back in the last four years of his life to the structure of the basin ranges, the problem that he 

 had opened up even before his first qualitative analysis of debris transportation. This 

 subject continued to occupy him until within a month of his death in 1918. 



Unhappily, by reason of failing health, this final return to the subject of his earliest 

 studies in the West was not carried to completion. It nevertheless included several field 

 excursions, on which a surprising amount of observation was accomplished. On the way to 

 San Francisco in 1914 he stopped for a fortnight or more to examine the western base of the 

 Wasatch Range near Ogden; one of his letters at that time notes: 



My last two days in Ogden were profitable. I struck some geology that will figure well in the next report. 



Of more importance was an excursion made in company with a friend from Berkeley in 

 1916 to the Klamath Falls district in southern Oregon, where some fault block ridges of very 

 recent displacement, as indicated by their exceptionally fresh scarps, had been discovered a 

 few years before. On the way there he noted that the eastern face of the Cascade Range at 

 the point where he crossed it appeared to be defined by a fault with a strong drop to the east 

 after the principal lava eruptions by which the range is largely covered, but before the erosion 

 of the deep canyons which now dissect it. Around Klamath, the relief was seen to be mani- 

 festly of tectonic origin; erosional valleys are found only in the upfaulted blocks, the inter- 

 mediate depressions are all aggraded. One fault scarp, worn away above and covered with 

 talus below, exhibits an intermediate part of its sloping surface over a length of 110 feet and 

 a height of 43 ; it is scored up and down with slickensides. In another such surface he found 

 the hade of the fault to be 70°, thus indicating a horizontal displacement three times greater 

 than the vertical. The field work was enjoyed, but writing an account of it progressed 

 slowly, for his health was only "holding its own and a little more." 



It was in the summer of this year, 1916, that a definite decision was made to return to 

 his old subject, the basin ranges: "I have taken up a new job," he wrote to a correspondent 

 while he was visiting his son in Utah, "to write on the structure of these mountain ranges. 

 It is an old theme for me, but I have data gathered in 1901 and 1914 and shall do a little field 

 work this year. . . . The mountains, and especially their bases, have stories to tell me." 

 He rode about in his son's car, and was surprised as well as pleased to see how readdy he 

 could thus cut across country through the sage brush. The Klamath excursion was apparently 

 a part of this new job. 



The Wasatch front was revisited in May and June, 1917, when several weeks were spent 

 driving along the foothills between Ogden and Provo. There also slickenslided surfaces were 

 found cutting off the rocks of the mountain front near its base at a relatively low angle and 

 thus indicating that a very considerable forward movement of the depressed block had accom- 

 panied its downthrow. During the winters of these later years Gdbert prepared the histori- 



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