10 



the town), the original floor of the valley was uncovered, and appears 

 as a slight elevation above the level of the rest of the lowland. In 

 general then the rock floor of the Connecticut Valley represents 

 this Tertiary plain which was developed in the softer sandstones. 

 Beginning with Mt. Toby and Sugarloaf the normal character of 

 eastward dipping blocks begins again and continues to the north end 

 of the valley. The small hill on which Amherst stands and Mt. 

 Warner are composed of so called Amherst Schist which is of Penn- 

 sylvanian age. Thus the general contour of the Valley was completed 

 about the end of the Miocene. (See Fig. 2, page 15.) 



Just after this a new uplift took place and the streams began anew 

 to cut deep valleys and seek a new base level. This was only attained 

 in the soft Triassic material, for in the Crystalline rocks the Micoene 

 base level had hardly been attained when the second uplift took 

 place. The Connecticut River cut a deep gorge, like that of the 

 Hudson River, but before any general widening took place, the ice 

 sheet of the Pleistocene spread over the whole country and buried 

 it. This undoubtedly scraped off some material and reduced the 

 irregularities, but did not materially alter the general contour. 

 During this period of being covered with ice there was a general 

 depression of the whole country until the Tertiary plain was below 

 present sea level. 



When the ice melted and the sheet retreated, leaving behind a 

 Moulder strewn surface and irregular moraines, it exposed a surface 

 so low that drainage was impeded. 



This low lying valley immediately filled with water making a 

 great lake. This great body of water was divided by the Holyoke 

 Range and its continuation the Tom Range and the Talcott Range 

 into two main bodies. What was north and west of these ranges is 

 called the Hadley Lake, while the water to the south and east of 

 the ranges is the Springfield Lake. The two however were connected 

 at several points by continuous water ways, one where the Connect- 

 icut River originally crossed the Holyoke Range, and another where 

 the Westfield River did the same. The old Lake shore approx- 

 imates the 300 foot level of today, and in many places can be easily 

 seen as terraces of gravel or sand. The lake bottom was gradually 

 covered with layers of clays varying from 10 to 180 feet thick, which 

 today are exposed in the numerous clay pits worked by the brick 

 making industries. (Fig. 1.) 



Amherst stands on what was an island in the lake, and the shore- 

 line is easily traced, appearing as the terrace just south of the geology 



