18 RURAL ^^EW YORK 



To consider the formations of the State in a little 

 more detail, though briefly, one may begin with the 

 oldest Precambrian areas. The Adirondack region 

 is the larger of these, the southeastern highland 

 above New York the pmaller. Both have a core of 

 plutonic rock centered by masses of granite. The 

 higher peaks of the Adirondacks in Essex County 

 belong to the granite group of rocks. Around 

 this core of acid rock is a much larger area of the 

 basic Gabbro rock, Norite, which skirts the base of 

 the mountains and reaches across the St. Lawrence 

 Eiver near its source where it forms the Thousand 

 Island group. This basic rock also extends well 

 down to the Mohawk Valley. 



In the second or southeastern area, the granite is 

 associated with gneisses and schist rocks which prob- 

 ably represent the transformation of ancient sedi- 

 ments by pressure and heat. Together these rocks 

 form the mountainous portion of that section. This 

 region does not again become prominent in geo- 

 logical processes until in Triassic time when the 

 bright red sandstones of lower Eockland County were 

 formed coincident witli similar formations through 

 the Connecticut Valley in New England, and in 

 various pockets throughout the Piedmont Plateau. 

 At its close the great cracks in the structure per- 

 mitted tlie intrusion from below of the molten mate- 

 rial that now forms tlie Palisades rock along the 

 lower course of the Hudson. The hard rock ridges 

 that reach under the site of New York City are an 

 important incident in its development, for they form 



