PHENOMENA AFFECTING RIVER THEORY 231 



and the glacial flood existed all that time, following the glacier. There- 

 fore the fill of the valley with the stream detritus proceeded from south 

 to north, and the volume of detritus would have been as great as if the 

 valley had been wholly filled its entire length at one moment. Considered 

 in its implications, this is an unreasonable amount. 



Disposition. — The fate of such an enormous volume of alluvial material 

 as the river theory requires is a serious difficulty. Where is the detritus 

 now? It had to be dropped when the river reached sealevel. To Dana 

 this was in Connecticut, in which case the broad valley should have been 

 filled below Hartford with a great delta plain. There are no remnants 

 of such plain; Even if such plain has been carried away, it should re- 

 appear farther south as a delta in Long Island Sound. 



The only recognition of this problem was by Upham, who suggested 

 that after the ice-cap disappeared the ocean might have stood beneath its 

 present level. But the Coast Survey charts do not indicate any sub- 

 merged deltas. 



The truth is that the valley never contained much more detritus than 

 it does today. The deposits from the tributary streams were laid along 

 the margins of the sealevel waters, but those from the glacial outwash 

 were swept into the open valley. During the subsidence of the waters 

 (land uplifting) some of the detritus was rinsed down the slopes and re- 

 accumulated at lower levels. The lower terraces are therefore of finer 

 material, more massive, more continuous, and with greater resemblance 

 to river plains, into which they blend at or near the valley bottom. When 

 the river came into life, which it did very gradually, such detritus as it 

 could grasp in its eroding stretches was dropped farther down in the 

 slack-water areas, forming the lower plains which we see today in the 

 southern part of the valley. 



Lower series of plains. — Upham refers to a set of lower terraces, more 

 continuous or connected in series than the upper, '^normal" terraces. He 

 suggested that they might indicate a pause in the river erosion. Such 

 hesitation in the relative lowering of the waters would really be due to a 

 relative pause in the rising of the land. It is possible that the rate of 

 uplift was not uniform. 



However, it may be that the series of more continuous plains only 

 represent the dominance of outflowing currents or initial stream-work, 

 at the lower levels^ over the static water effects which dominated at the. 

 higher levels. 



The lower, broader plains have an altitude in the Few Haven-Hartford 

 region of about 100 feet, at Springfield about 200 feet, and at Brattleboro 

 about 300 feet. They lie something like 100 feet beneath the summit 



