1913] The Moraine Systems of Southwestern Ontario. 65 



lake waters occupied the area as soon as the ice withdrew. This left the 

 island still bounded by ice on all sides, excepting a small part at the 

 southwest end which had a shore of lake water instead of ice. 



In a general way, this condition continued for a relatively long 

 time. The central part of the peninsula was still an island in the true 

 sense, until late in the glacial recession. After a time, however, it came 

 to have a longer shore of water than of ice, but it did not expand so as to 

 be separated from the adjacent mainland only by the narrow waterways 

 of the St. Clair, Detroit and Niagara rivers until quite late in the glacial 

 recession. As the ice front withdrew the island expanded both by the 

 melting back of the ice and by the falling of the lake waters to lower 

 levels. The progress of this expansion will be noted below as the suc- 

 cessive steps of retreat marked by the moraines are described. 



On the accompanying map most of the moraines have been given 

 names, generally the names of towns through or near which they 

 pass. Fragments are also named, where they are of any length. The 

 names are applied merely as a matter of convenience in description, 

 and while those of the longer moraines may perhaps stand permanently, 

 the names of some of the fragments will probably be only temporary, 

 for future studies in the field will no doubt show that they are not inde- 

 pendent moraines, but are parts of one individual. In such cases the 

 names will have to be revised at some later time. 



Moraines of the Lake Huron Ice Lobe. 



The moraines formed along the east side of the Lake Huron ice lobe 

 have not been fully investigated, especially in the fiat, low region south- 

 west of London, where they become faint, waterlaid forms, but nine or 

 ten moraines belonging to this group have been mapped. 



I. The Essex Moraine. — This moraine, known as the Detroit moraine 

 in Michigan, extends from Detroit southeastward through E^sex to the 

 high knoll west of Leamington. Its relation to the ice lobes has not yet 

 been clearly worked out. In Michigan its descent down the slope from 

 Birmingham to Detroit transverse to the valley axis suggested an inter- 

 lobate origin, but the part in Ontario seems more like a moraine of the 

 Lake Huron ice lobe. If it was interlobate in origin it was subglacial, 

 but if it was a simple, terminal deposit it was laid down in about 200 

 feet of water. This moraine is a low, broad ridge of till, very smooth 

 and with such gentle side slopes as to be quite inconspicuous to the eye 

 as a ridge. It has, nevertheless, a relief above the fiat lake plains around 

 it of 12 to 15 feet. At present the relation of this moraine to the others 

 farther north and belonging to the Lake Huron lobe is not known. The 

 intervening area has not been studied. 



