50 TARR AND MARTIN CHANGES OF LEVEL IN YAKUTAT REGION 



since developed to their former condition. We found other less definite 

 evidence of the recent presence of a destructive water wave in several parts 

 of the fiord. 



Evidences of recent Faulting 



recent faults on gannett nunatak 



At several places small faults of recent date were observed. The best 

 and most typical instance is that on Gannett nunatak, which separates 

 the land and sea ends of Nunatak glacier at the head of Nunatak fiord 

 (see plate 23). This rock hill, reaching an elevation of about 1,450 

 feet, is made of steeply dipping gneisses and schists, striking northwest- 

 ward approximately parallel to the major axis of the Saint Elias chain. 

 The nunatak is double crested, and the -southern half is crossed by scores 

 of small faults (plate 20, figure 2), extending continuously from a few 

 feet to over 200 yards, and with throws varying from an inch to 3 or 4 

 feet (plate 21, figure 1), but usually less than a foot. They extend ap- 

 proximately along the strike of the rock (north 40 degrees west, true 

 north), but some small faults diverge from it, and a few short ones extend 

 at right angles to the strike, connecting neighboring strike faults. The 

 hade is nearly vertical, and in almost all cases the southwestern side of 

 the fault is the upthrow side, though there are a few with an upthroAv on 

 the northeastern side. There are some fissures (plate 21, figure 2) and 

 a few instances of small graben blocks (3 to 30 feet wide) between 

 parallel faults (plate 21, figure 2). Some of the faults were traced up 

 to the glacier under which they apparently passed. 



Glacial scratches extend up to the edges of the faults and are there dis- 

 located, and no striae occur on the faces of the fault-scarps. Here and 

 there the faults have dislocated a thin till veneer on the rock. These 

 facts prove that the faults have developed since the ice receded from the 

 slopes of the nunatak, not many decades ago, and possibly since Eussell 

 first saw it in 1891. That they are very young is proved by the sharp 

 angles formed where the fault planes intersect the surface, even when the 

 surface material is till, and by the general absence of notable talus slopes 

 at the base of the tiny fault-scarps. It seems incredible that these fault- 

 scarps can have been exposed to the weather longer than six years; and, 

 although it can not be more positively demonstrated, this faulting is con- 

 fidently correlated with that deformation of the crust which elsewhere 

 in the region has been definitely determined to have occurred in 1899. 



RECENT FAULTING AND AVALANCHES 



Our first observations of minor faulting and rock fracturing were made 

 near the edge of a cliff just southwest of cape Enchantment ; but the posi- 



