PLEISTOCENE MARINE SUBMERGENCE 23 



Plate 9. This map relates to the diastrophic problem, the 

 deformation of the continental surface. The amount of uplift out 

 of the sea is approximately shown by the isobases for all of the 

 State and the neighboring territory. The map is to be used in con- 

 nection with the tabulated data, plate 12. 



In the Hudson-^Champlain and Connecticut valleys the estuar}% 

 sea-level waters have left a record of the submergence in the shore 

 features. The height of those features today is the measure of the 

 postglacial uplift. The lines of equal uplift, isobases, connect 

 points of equal rise in the two valleys ; and the -lines have been 

 extended westward across the State. Across New York the 

 isobases have nearly direct courses, 20 degrees north of west by 

 south of east. It is recognized that the extended isobases must 

 lie in circles or ovals about the domed area of uplift, and that both 

 east and west they must be given decided curvature. On the east 

 the curvature is determined by study of the land uplift in New 

 England. Westward the curvature is hypothetic. 



The lines of 300 and 400 feet are located in accordance with the 

 determinations of Professor Emerson (66, 6y). The zero isobase 

 should, it is probable, be laid farther south, but as it is an uncertain 

 and elusive element the line is drawn well within the limits of the 

 map. 



It will be seen that the rate of tilting, or gradient, of the shore 

 line increases toward the north, as indicated by the spacing of the 

 isobases. From present knowledge it appears that the steepest 

 gradient lies over the Champlain district, and that the surface of 

 the dome of uplift has a decreasing slope in Canada. The height 

 of the estuary ifeatures in Lake Memphremagog district have 

 located the 800 feet isobase. 



Plate 10. This profile has been drawn to connect points oif 

 clear summit shore features. These stations are numbered on tlie 

 chart, 10, 22, 24, 50, 54, 58, 78, 89, 138, 144. The fact that nearly all 

 the topmost shore features, even in localities as far away as the 

 Connecticut valley and the east shore by the Green mountains, 

 coincide ven;- closely with this profile is confirmation of its accu- 

 racy. And the vertical relation is greatly exaggerated, as the 

 vertical scale is 528 times the horizontal. 



Since the isobases are inclined 20 degrees from the latitude 

 parallels and this profile is for a meridian, the proper location of 

 the stations is by the intersection of their isobases, and the results 

 are surprisingly harmonious. In only three localities are summit 

 bars found at heights above this profile. These are at Crown Point, 



