SUBAERIAL DIVISION. 49 



Lafayette terrace. — The highest of the five terraces is known as the 

 Lafayette. It is best developed in Virginia along the western margin of the 

 province, capping the broader divides between the main streams. The 

 surface of this terrace varies considerably in appearance according to its 

 position. In some places in the interior of large areas where it is removed 

 from the influence of streams, it is as flat and featureless as any portion of 

 the Eastern Shore, but along the margins where it has been dissected by 

 waterways, it has been transformed into a gently rolling country. Erosion 

 has been so active since the formation of the Lafayette terrace that isolated 

 remnants of the original surface are frequent, some of them occurring as 

 outliers upon the Piedmont rocks, while other detached areas lie to the 

 east of the main body. Could the intervening areas be filled in, we would 

 have a continuous, gently-rolling to flat plain of variable width, extending 

 from eastern Pennsylvania southward to Mexico. 



The general slope of the Lafayette terrace is eastward toward the ocean 

 and represents, as will be explained later, the gradual descent of a sub- 

 aqueous terrace away from the shore-line out into deeper water. In some 

 places the terrace has been slightly warped by earth movements and thus 

 the normal slope is obscured. The highest portion of the Lafayette terrace 

 thus far recognized in Virginia lies to the west of Palis Church in Fairfax 

 County and has an elevation of between 480 and 500 feet above sea level. 

 It gradually descends from this point to the eastward along the stream 

 divides to an altitude of about 200 feet, where it ends at the escarpment 

 marking the landward margin of the Sunderland terrace Added details 

 regarding the distribution and character of this terrace will be given under 

 the discussion of the Lafayette formation. 



Sunderland terrace. — Bordering the Lafayette terrace at a lower level 

 is the Sunderland terrace. It penetrates the former in re-entrants and is 

 at times separated from it by a well-marked scarp line. This terrace surface 

 has its greatest development in the central part of the province. From 

 Stafford County to Greenesville County it is represented as a fringing terrace 

 along the sides of larger valleys whose divides are formed by the Lafayette 

 terrace. This relationship of the Sunderland to the Lafayette terrace is 

 always found wherever the two occur in juxtaposition. The difference in 

 altitude between them varies, generally becoming more marked to the west- 

 ward toward the Coastal Plain border. The passage from the Lafayette to 

 the Sunderland is gentle, but occasionally it is accomplished by means of 

 an abrupt drop resembling in appearance a sea-cliff which, has been more or 

 less modified bv subaerial erosion. 



