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Sierra Club Bulletin. 



Plate XXXL — Dome Structure near Emerick Lake. 



Figure i. — Hill southeast of Emerick Lake, Upper Merced Basin, 

 Sierra Nevada. 



The hill, which is about 250 feet high, is the terminal and 

 culminating points of a long ridge of granite. The dome 

 structure in the ridge is anticlinal, changing in the hill to 

 the inverted canoe form. At the extreme right the convex 

 or anticlinal curvature is seen to merge into a concave or 

 synclinal curvature, better shown in figure 2. The hill was 

 deeply buried by a glacier moving from left to right. Gla- 

 cial erosion made the rock basin occupied by the lake and 

 excavated the hillside so as to expose the dome structure in 

 partial section. 



Figure 2. — A Syncline in dome structure. 



Emerick Lake (Figure i) lies out of sight, just beyond 

 the granite slope at right. Its outlet, crossing the sill with- 

 out notable incision, descends to the foreground at left. 

 Structure and topographic configuration are in harmony. A 

 syncline pitches toward the foreground and also (slightly) 

 toward the lake. At the lip of the lake basin the cross- 

 section is synclinal and the longitudinal section anticlinal. 



Plate XXXIL — Joint Structure and Fire-S palling. 



Figure i. — Jointed granite in Kuna Crest, Sierra Nevada. 



The granite is traversed by four systems of parallel plane 

 joints. The cliff is at the head of a glacial cirque, and the 

 sloping plain above it belongs to preglacial topography. 

 The general forms of cirque and plain are independent of 

 the attitudes of the joint systems. Compare with Plate 

 XXXI, and observe the contrast between joint structure 

 and dome structure. 

 Figure 2. — Granite boulder from which spalls or flakes have been 

 riven by the heat of forest or meadow fires. 



The spall at the left, still standing in position, illustrates 

 'I approximate parallelism of fractures thus produced to 

 exterior surface. Probably in this case the strong heat- 

 was at the side and local — as the heating would be, for 

 iple, if the log at the right should be burned — and the 

 size of the spall was determined by the localization 

 - heat. 



