MARYLAND GEOLOGICAL SURVEY 181 



the terrace now forming are compared "with those which accompany 

 the various terraces of the Columbia group, the analogy is found to 

 be so striking that the conclusion regarding a common origin of both 

 is irresistible, and there can be no reasonable doubt that the mode of 

 formation of the modern terrace furnishes the key to the interpreta- 

 tion of the ancient. 



The earliest of these ancient terraces of the Columbia group has 

 been assigned to the Sunderland formation. This terrace occupies 

 the highest topographic position of the series, and ranges from an 

 altitude of 90 to about 180 feet. 



The subsidence of the Atlantic Coastal Plain, which carried down 

 the southern half of Cecil county checked somewhat the erosion which 

 had been destroying the Lafayette* deposits and caused the deposition 

 of the Sunderland formation. As Cecil county slowly sank beneath 

 the water, the shore of the advancing Atlantic gradually crept further 

 and further westward, until it finally came to rest in a circuitous line 

 extending from near Erenchtown on the Susquehanna river northeast 

 to Belvidere, approximately in the position now occupied by the Bal- 

 timore and Ohio Railroad. From here the coast-line passed south of 

 Toys Hill and on to Leslie; it then turned southward and encircled 

 the western, southern and eastern flanks of the Hog Hills, and then 

 northward again to Childs, Singerly, Banks and Iron Hill where it 

 passed out of the State. Grays Hill and the highest portions of Elk 

 Neck south of the Hog Hills rose above the sea as islands. How 

 long the sea remained in this position is not definitely known, but it 

 is known that it stood there long enough to cut a well-pronounced 

 sea-cliff along a large portion of its border. This ancient sea-cliff 

 has since suffered greatly from erosion and in many places is nearly 

 obliterated but in other localities may be distinctly seen to-day form- 

 ing a prominent feature in the local topography. Among the best 

 localities for viewing this ancient sea-cliff may be mentioned the 

 abrupt rise one-half mile north of Aiken extending from the Blythe- 

 dale road eastward toward Jackson, again around the flanks of Toys 

 Hill, near Leslie, on the slopes of the Hog Hills, at Elk Neck and 

 Bull Mountain. The scarp line north of Elkton in the vicinity of 



