BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 22, pp. 681-686, PLS. 30-31 DECEMBER 7, 1911 



CIRQUES AND ROCK-CUT TERRACES OF MOUNT TOBY^ 



BY B. K. EMERSON 



(Offered to the Society for Publication October 21^, 1911) 



CONTENTS 



Page 



Introduction 681 



The cirques 681 



The terraces 684 



Introduction 



Mount Toby, in Sunderland, 8 miles north of Amherst, is the highest 

 elevation in the Triassic area in Massachusetts. 



It presents two- unique topographic features — one a group of radiating 

 cirques which show many of the characteristics of glacial cirques, but 

 which may seem to be on too small a scale to have this origin, and the 

 other a series of rock-cut terraces with vertical walls 10 to 150 feet high, 

 which are confined to the west side of the mountain. 



The Cirques 



I owe iiie bird's-eye view of the mountain (plate 30, figure 1), which 

 shows the condition of things with great clearness, to the skill of my 

 daughter, Mrs. Charlotte E. Hitchcock. There is some necessary exag- 

 geration and some intentional disregard of the ordinary laws of shading 

 in order to bring out all the steep-walled radiating depressions. 



The cirques do not appear so clearly as they should on the topographic 

 map of the mountain, because the contour lines are there drawn so as not 

 to touch where walls GO feet or more in height are quite vertical. These 

 contours are generally very incorrect, and especially so in two important 

 places. The main ridge of Mount Toby should be continued south beside 

 the railroad a mile farther than is shown on the map, and the deep de- 

 pressions in the southwest side of the mountain are omitted, as well as 

 the corries at the north end. 



1 Manuscript received by the Secretary of the Society May 31, 1911. 



XLV — Bull. Geol. Soc. Am., Vol. 22, 1910 (081 



