GEOLOGY OF THE ISLAND. 267 



known as Cape Hatteras, in a southwesterly direction. The island's 

 greatest width near its lower end falls short of 3 kilometers; the aver- 

 age width is only 1 kilometer, while in places it is even narrower. 

 Outside rolls the Atlantic, while between island and mainland stretch 

 the waters of Pamlico Sound, here from 30 to 45 kilometers (18 to 27 

 miles) wide. Pamlico differs from the shallower Albemarle Sound to 

 the north in the important respect that its water is always salt, while 

 Albemarle is normally fresh. 



Near the southwestern extremity of the island a broad expanse of 

 tidal fiat separates the higher land of the village of Ocracoke from 

 the Atlantic beach. One and one-half kilometers or so toward the 

 northeast this lagoon disappears, ami dry land extends from the flat 

 sandy beach and the salt marshes which border the Sound to the 

 dunes which front the ocean. Into these marshes penetrate tiny 

 creeks, whose ramifications cut the lower part of the island in all 

 directions. Almost the whole area is divided between sand strand 

 and tidal marsh. Much of it is only 1 meter or less above normal 

 high tide and subject to overflow when strong easterly gales are blow- 

 ing, or when stiff breezes from the opposite quarter mass the waters 

 of Pamlico Sound against the western shore of the island. The high- 

 est land on Ocracoke is represented by sand dunes often 3, sometimes 

 8 meters high. These are usually regular in form and fairly well 

 fixed by the vegetation. Those that abut upon the outer beach or 

 rise amid the mud flats are particularly regular and dome-shaped. 



GEOLOGY AND SOILS. 



Of the geology of Ocracoke and its neighbor Hatteras, we have 

 comparatively little knowledge. Shaler 1 has advanced the theory 

 that these reefs were built up from the detritus which resulted from 

 the glacial excavation of Delaware and Chesapeake bays. Kerr 3 

 describes Hatteras as a "sort of delta." "The action," he says, "of 

 the tides and ocean currents, the Uulf stream and Arctic current 

 meeting at this point, accumulates upon Hatteras the river silt which 

 reaches the sea by way of the Chesapeake as well as that of the rivers 

 which discharge their burdens through the inlets about this point and 

 southward. * * * Hatteras is not a modern phenomenon, It is 

 at least as old as the Cretaceous; the Quaternary as well as the Ter- 

 tiary of this coast region of North Carolina are laid down upon an 

 eroded surface of Cretaceous rock." From measurements elsewhere 

 made, the probable depth beneath the surface of the Cretaceous for- 

 mation on Hatteras and Ocracoke would be somewhere between 200 

 and 300 meters. lam not aware that borings of any considerable depth 



'Proc. Boat. Soc. Nat. Hist., vol. 14, pp. 110 to 121. 1872. 

 ,J Bul. Wash. Phil, fc'oc. vol. «, pp. 28 to 3U. 1884. 



