RELIEF. 37 



the trend of the other topographic features. Moreover, the slates break 

 off, forming steep chffs that surround the ridges and hills, instead of the 

 moderate slopes more common in the western part of the district. The 

 valleys are almost flat and are exceptionally wide. In short, the wide 

 U-shaped form is the common one here, rather than the flaring V-shaped 

 valley characteristic of rivers. The modification of the topography from 

 the V-shaped to the U-shaped forms is attributed to glacial erosion and 

 deposition. 



One area in which rather interesting topography was observed is 

 that extending from about IJ miles southeast of Ely, in sec. 2, T. 62 N., 

 R 12 W., southwestward to sec. 30, T. 62 N., R. 12 W., including about 

 14 square miles. This area is underlain by the Giants Range granite, and 

 throughout the relief is very slight, the greater portion of the land surface 

 being only a foot or so above the level of the lakes. As a result the major 

 portion of it is a marsh. The knolls are of granite, with low, rounded 

 surfaces rising only a few feet above the swamp area. A few of the knolls 

 are composed of glacial drift. Evidently pre-Grlacial di-ainage had been 

 es2Decially vigorous here, and this is a small, nearly base-leveled area, with 

 the lakes as the base-level. 



On a reconnaissance trip along the international border a similar 

 area was noted surrounding the southeast side of Iron Lake, in sees. 

 11 and 12, T. 66 N., R. 13 W., and sec. 7, T. 66 N., R. 12 W., outside of 

 the Vermilion district. Here base-leveling has proceeded farther than in 

 the area previously mentioned; the islands in this portion of the lake rise 

 just above the water level, and the small streams entering the lake here 

 flow with meandering courses through wide marshes. 



The gabhro plateau. — In northeastern Minnesota, southeast of the 

 Vermilion district proper, there is a large area underlain by gabbro. Only 

 a small poi'tion of this area comes within the region shown on the accom- 

 panying general map, and that portion is a strip on its southern and 

 southeastern edge. Knowledge of the plateau has been derived from a 

 study of tliis strip, where for the most part stratigraphic work ended; from 

 the results of a reconnaissance trip within the area underlain by the 

 gabbro; and chiefly from the description by Dr. U. S. Grant in the last 

 Minnesota report, " to which the reader is referred for greater detail. Dr. 



aGeol. and Nat. Hist. Survey of Minnesota, Final Kept., Vol. IV, 1899, pp. 434^436. 



