PHYSIOGRAPHY OF THE VIRGINIA COASTAL PLAIN. 47 



evidence of the abundance of moUuscan forms inhabiting the region, while 

 here and there occur local deposits of pebbles and also of blue mud. 

 Seaward the deposits become finer until in the vicinity of the continental 

 slope muddy deposits predominate. 



OFF-SHORE BEACHES AND BARS. 



As the large waves from the deeper parts of the Atlantic Ocean advance 

 toward the land they finally reach a place where the lower part of the wave 

 drags on the bottom. The unconsolidated material is carried landward 

 until the wave finally breaks. The smaller wave current then continues to 

 carry part of the fine sand forward. Some is carried back by the undertow- 

 current, while some is left heaped up in a ridge formed parallel to 

 the advancing wave front. Thus in time a chain of sand-bars which may 

 l)ecome considerable islands is formed a short distance from the former 

 shore-line and with each succeeding storm these are either enlarged or cut 

 away. As these increase in size sand dunes form upon them and thus the 

 elevation above the sea may become so great that the largest storm waves 

 never sweep over them. Bordering the eastern shore of the State is a chain 

 of long, narrow, low-lying sandy islands formed in this way, and separated 

 from each other by narrow inlets through which the tide enters and leaves 

 the lagoons formed back of the islands. Many of these islands are very 

 narrow and scarcely rise above the water, but others are a mile or more 

 in width and are inhabited by considerable colonies of fishermen. The most 

 important of these islands are Chincoteague, Assateague, Metomkin, 

 Paramores Beach, Hog, Cobbs, and Smith on which is located the Cape 

 Charles light house. 



COASTAL LAGOONS. 



Between the sandy beaches Just described and the shore is a series of 

 shallow-water lagoons of variable width from one-half mile to six or eight 

 miles. Bordering these on either side is usually a considerable belt of salt 

 to fresh water marshes. The average depth of water is only three or four 

 feet, except in the channels through which the tide enters and leaves. The 

 amount of water flowing through the narrow inlets between the islands is so 

 great that occasionally very strong tidal currents are produced, currents 

 strong enough to scour out relatively deep channels. Thus the channel of 

 Great Machipongo Inlet between Hog and Cobbs islands is in places over 

 60 feet in depth while that of Sand Shoal Inlet between Cobbs and Bone 

 islands has a maximum depth of 72 feet. The bars and hooks formed off 



