NEWARK ROCKS OP ROCKLAND COUNTY, N. Y. 23 



This extreme narrowness is due to a slight extent to the way the 

 glacial drift is banked up against the southwestern margin. But 

 the actual thickness of the sheet here is undoubtedly much less 

 than farther south. At Long Clove its width is about 100 rods, 

 and near High Tor, at Haverstraw, from f to f of a mile. West- 

 ward its width slowly decreases, till the rock is last seen at a 

 small outcrop in the railroad cut south of Mt Ivy station on the 

 New Jersey and New York railroad. 



Eight. In general the trap rock forms a high massive ridge 

 with a steep and in places precipitous eastern or northern face 

 and a much gentler westward slope. Locally the latter is as 

 steep as any part of the eastern face except where the former is 

 marked by high cliffs. The hight above the river varies greatly. 

 Just north of the state line the top of the ridge is broad and flat, 

 and barely 200 feet above sea level. Southward in New Jersey it 

 rises to hights of about 550 feet, whence it descends gradually 

 and regularly to sea level at Bergen Point. The New Jersey Pali- 

 sades are distinguished for the evenness of their crest line and 

 the absence of deep gaps or notches. This is not the case in New 

 York. At Sparkill the broad 200 foot gap is cut through almost to 

 sea level by the gorge of Overpeck creek. Northward the crest line 

 rises abruptly to a series of knobs whose hights range from 600 to 

 700 feet. On the very summit of one of these knobs is perched a 

 huge glacial boulder of gneiss, shown in plate 1. West of Nyack 

 the sag in the ridge is only 240 feet above the sea level. The hight 

 at Hook mountain is 730 feet; east of Rockland lake 610 feet; at 

 High Tor, where the maximum is reached, 832 feet; and at Little 

 Tor 710 feet. Where it disappears in the railroad cut, the eleva- 

 tion is 440 feet above the sea. Between Nyack and Haverstraw 

 the ridge is broken by four gaps, the bottoms of which have closely 

 accordant altitudes, as shown by these figures: Rockland Lake 

 210 feet, Trough Hollow 190 feet, Long Clove 230 feet and Short 

 Clove 210 feet. 1 Plate 2 shows the two latter gaps as seen from 

 the southern side of the ridge. In addition to these there is be- 



lThese hights are taken from the U. S. topographical atlas, and are sub- 

 ject to a plus or minus correction not exceeding 10 feet, provided the map 

 is accurately drawn. 



