108 J. W. SPENCER — RECONSTRUCTION OF ANTILLEAN CONTINENT. 



lakes we have been able to measure the recent deformation of the earth's 

 crust, since the abandoned shores rise from zero to three, six or even more 

 feet per mile toward the northeast, as shown in figure 4. The deforma- 

 tion is also recorded in the variable altitudes of the recent geologic 

 formations shown in figure 5. Everywhere the movement of elevation 









so . 





100 M 



iLtS 



17 00 



Fzn 



t' 





T 



-^ 













'^ 





H 



1^ 





|3 







Y' 



1' 



Figure ^. — Section of the Iroquois Beach. 



A raised waier-line from the head of lake Ontario for about 400 iniles to south of Malone in the 

 Adirondacks. The rise increases from an elevation of 363 feet above tide near the lake to 1,482 

 feet in the mountains, where the greatest deformation occurs. 



appears to be greater in the mountain regions than on the plains, and it 

 is noteworthy that the rate of depression along the coastal margins seems 

 larger than farther inland. The epeirogenic movement does not gener- 

 ally deface the topographic features, although it sometimes changes the 

 direction of the drainage and turns the valleys into basins ; and in this 



12 16 HUNDRED 



Figure 5. -Section from South Carolina to the Mississippi, shoiving Deformation of the Lafayette 



Formation. 



At Columbia, South Carolina, the elevation of the Lafayette formation is about 800 feet above 

 tide; in the mountains farther westward it has double that altitude, and in Arkansas less than 300 

 feet. 



respect it has been an important factor, inclosing the Mexican, Honduras 

 and Caribbean valleys into sea basins, though orogenic and volcanic forces 

 also combined with the gentler terrestrial undulations in producing these 



abysses. 



Submarine Valleys and Fjords of the Continental and Antillean 



Regions. 



THE CONTINENTAL SHELF. 



In passing southward from New Jersey the continental shelf narrows 

 to only about 15 miles wide off cape Hatteras (section F F' on accom- 

 panying map), but from that point it widens to nearly 300 miles east of 

 Florida. Although crossed by the straits of Florida and the Gulf Stream, 

 the plateau embraces the Bahamas, east of which its broken remains 

 rise in banks north of Haiti and beyond it has been largely swept away. 

 This shelf has been mostly removed by denudation, only fragments, of 

 it remaining east of the Windward islands, but off the coast of South 



