MARYLAND GEOLOGICAL SURVEY 67 



Lafayette terrace continues on through Virginia southward to Florida 

 and Texas and over into Mexico. It is believed that at one time these 

 scattered remnants of the Lafayette terrace were united in a continuous 

 whole and that their present isolated condition had been brought about 

 by erosion. If we assume that they were once continuous, it will be a 

 simple matter to establish the present attitude of this terrace, notwith- 

 standing the fact that its surface has been somewhat modified by erosion. 

 In the Piedmont region of Cecil county the surface of the Lafayette 

 terrace lies at an altitude of 470 feet. This rises to about 500 feet in 

 the vicinity of Lochraven and Catonsville near Baltimore, to 486 feet at 

 Burtonsville, Montgomery county, and sinks again to 400 feet in the 

 District of Columbia. Thus we see over a distance of about 80 miles 

 that the surface of the Lafayette is extremely uniform. This direction 

 is, however, from northeast to southwest and approximately parallel to 

 the trend of the modern coast line. If, now, the altitude of the Lafayette 

 terrace is examined at right angles to this direction, namely, toward the 

 southeast, it is found that on the high hills of Elk Neck, in Cecil county, 

 the surface of the Lafayette terrace lies at about 300 feet, making a 

 slope in Cecil county of 170 feet in a distance of about 10 miles. At 

 Charlotte Hall, St. Mary's county, the surface lies at a height of about 

 200 feet, making a slope between the District of Columbia and Charlotte 

 Hall of 200 feet in a distance of about 36 miles. It will thus be seen 

 that the surface of the Lafayette terrace has a slight incline toward the 

 southeast or, in other words, slopes gently toward the ocean." 



6 It will be explained later that this slope represents the gradual descent of 

 a sub-aqueous terrace away from the shore-line out into deeper water. The 

 elevation at the foot of the scarp represents the altitude of the old shore-line 

 which, on account of oscillations in level, has been somewhat thrown out of a 

 horizontal position since its formation, so that it lies at slightly different alti- 

 tudes in various portions of the Coastal Plain. The altitudes recorded away 

 from the scarp-line, show the elevations of the sub-aqueous terrace at varying 

 distances from the ancient shore.' These also have been slightly thrown out 

 of their original position so that their former level attitude is now somewhat 

 obscured. In any one locality, however, the various terraces, from the oldest 

 to the youngest, occupy distinct levels and are usually separated by pro- 

 nounced scarps, but when distant localities are compared the shore-line of one 

 bench may be found to correspond in altitude at the present time with the 

 deeper water phases of the next higher bench. This discrepancy, as has just 

 been said, is due to tilting, and will be fully explained below. 



