14 RURAL A^L'W YORK 



THE STRUCTURAL GEOLOGY (See FigS. 1-3) 



The underlying geological structure of New York 

 is very ancient. Its formations represent the dawn 

 of the land areas of the American continent. Great 

 mountain chains and plateaus have been formed and 

 largely destroyed by erosion. New York lies on the 

 west slope of the narrow ridge of land extending 

 from New England to northern Georgia that formed 

 the original backbone of the North American conti- 

 nent. For ages nearly all of the territory of New 

 York was beneath the ancient ocean and received the 

 succession of sediments and deposits washed from the 

 upland to the east. The floor of this sea oscillated 

 up and down unequally, somewhat like the billowy 

 waves passing over a grain field, only vast periods of 

 time were required for the movement. Sandy shores, 

 mud flats, deep clear water and alkaline basins suc- 

 ceeded each other in their occupancy of the territory. 

 The waste sediments from the upland came in from 

 opposite directions and were, therefore, of different 

 character. All these incidents are recorded in the 

 great succession of rocks that now make up the struc- 

 ture of the State. With the exception of the Adiron- 

 dack region, practically all the surface rocks are 

 made up of marine sediments and accumulations, 

 and their total depth is measured in miles rather than 

 in feet. They begin in pre-Cambrian time, which 

 was before the dawn of rock formations distinguish- 

 able by fossil remains of plants or animals. Vast 

 successions of time are represented in rock strata that 

 reach through the Lower and Upper Silurian and 



