consist largely of glacial till and the Holocene deposits consist largely of 

 fine-grained lake sediments. About 14,000 years before present (B.P.) a glacial 

 lake occupied the Lake Erie basin to an elevation of about 244 meters above sea 

 level (Sly, 1976). Within the next 1,400 years or so, lake level fluctuations 

 of a few tens of meters took place as the receding glacier, in a series of 

 retreats and advances, alternately exposed and buried different lake outlets. 

 The glacial activity ended about 12,600 years B.P. with retreat of the last 

 Wisconsinan glacier. This allowed the lake waters to discharge northeastward 

 across the Niagara escarpment, which at that time was depressed due to the 

 weight of the glacier. Because this outlet was about 40 meters below present 

 lake level, the level of early Lake Erie was at about 134 meters above sea 

 level. Subsequent isostatic rebound of the escarpment at the outlet led to the 

 filling of the lake to its present elevation of about 174 meters above sea 

 level. 



2. Shore . 



The shore from Conneaut to Huron consists of moderate to high relief (3 to 

 20 meters) shale and till slopes and bluffs commonly capped by old lake deposits. 

 The shale is exposed for appreciable lengths above or near lake level from 

 Conneaut to Fairport Harbor, near Euclid (Moss Point), between Cleveland and 

 Avon Point, and near Vermilion. The shore from Huron to Marblehead consists of 

 low relief (<2 meters) barrier beaches and laminated clay banks. The shore at 

 Marblehead consists largely of moderate relief (3 to 6 meters) dolostone and 

 limestone banks. 



Beaches make up a fragmented band that front about 50 percent of the shore 

 in the study area. The beaches are commonly narrow (<15 meters wide) and 

 consist primarily of sand, although there are pocket beaches of cobbles in 

 places where the shore is composed of rock. In addition, there are about 3,000 

 shore protection structures consisting largely of groins and seawalls scattered 

 along the shore. 



3. Offshore . 



Lake Erie is the shallowest of the five Great Lakes with an average depth 

 of about 19 meters and a maximum depth of 65 meters. The nearshore slopes are 

 generally less than 1°; in the study area within 1 to 2 kilometers of the shore 

 the slope is about 0.25°, except between Fairport Harbor and Avon Point, where 

 the slope is about 0.50°. Offshore the slopes become gentler with a slight 

 decrease in slope from east to west; the area off Lorain-Vermilion is the prin- 

 cipal exception. In this area the offshore bottom rises to form a subtle ridge 

 (Pelee-Lorain ridge) which extends across the lake to Point Pelee, Canada. 

 Sand and gravel, generally less than 2 meters thick, cover much of the near- 

 shore (<1 kilometer offshore) bottom; most of the bottom farther offshore is 

 made up of fine-grained postglacial sediment, rock, till, or glaciolacustrine 

 clay (Verber, 1957; Hartley, 1961; Williams, et al., 1980). In general, the 

 distribution of these offshore deposits (to the international boundary) can be 

 divided into two areas: from Conneaut to Fairport Harbor, a band of shale is 

 bordered offshore by sand and finer postglacial sediment; from Fairport Harbor 

 to Marblehead, a band of sand and gravel, till, or rock (mostly shale) is 

 bordered offshore by finer, postglacial sediment except for till in the 

 Cleveland area and sand and gravel in the Lorain-Vermilion area. 



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