REPORT OF THE DIRECTOR AND STATE GEOLOGIST 1901 vll 



i 



THE NORTHUMBERLAND VOLCANIC PLUG 



BY J. B. WOODWORTH 



In the summer of 1901, the writer, in making a reconnaissance 

 of the Pleistocene deposits of the Hudson valley in the vicinity 

 of Schuylerville, came on an undescribed occurrence of igneous 

 rock in the form of a low knob in the town of Northumberland. 

 The accompanying map, plate 2, shows the position of this 

 small knob, about 1 mile north of the village of Schuylerville, on 

 the west bank of the Hudson river. 



The right bank of the Hudson river here consists of the usual 

 bluff of Hudson river slates partly masked by Pleistocene clays. 

 The igneous rock, being more resistant to erosion than the 

 fragile slates, has withstood better the glacial erosion to which 

 the region has been subjected and therefore stands out as a sort 

 of buttress from the main wall of the inner Hudson valley or 

 gorge. Much like the volcanic necks and plugs about Edinburgh 

 in Scotland, this hard mass has been deeply scoured at base on 

 the ice-struck side. In fact, all of the present relief of this plug 

 and the adjacent river valley is due to the action of the river 

 combined with that of the ice sheet of the glacial period. 



The summit of the knob scarcely attains the level of the up- 

 land which lies west of the river. A slight depression west of the 

 plug serves to give it the appearance of a low knob (pi. 3) when 

 viewed from the upland, but at a distance it is relatively incon- 

 spicuous. This fact, taken in connection with the dark color of 

 the rock in which respect it closely resembles the adjacent Hud- 

 son series, perhaps accounts for its going so long unnoticed or at 

 least undescribed by the geologists who have passed through the 

 upper Hudson valley. There is no mention of the knob by Peter 

 Kalm or later observers; yet it appears from Brandon's 1 histori- 

 cal map of Old Saratoga that General Stark of the American 

 army occupied the eastern base of this knob during the battle of 

 Saratoga. Until the knob shall have been dug away for road 

 metal, it seems not inappropriate to designate it as Stark's 

 Knob, and that name will be used in this paper for convenience 

 of reference. 



1 Brandon, Rev. John Henry. Story of Old Saratoga. Albany 1900. 



