pre-Cambrian rocks in general results in more rugged land forms 

 while the sedimentary rocks result typically in level or low-relief 

 forms. 



Much of this area was glaciated during the most recent ice age 

 which covered most of Canada with a sheet of ice several thousands 

 of feet thick. There are today several areas of permanent ice caps. 

 Glaciers and snow fields cover large sections of Ellesmere Island, 

 Devon and Bylot Islands, and northeast Baffin Island. As a result 

 of the decrease in load when the main ice sheet retreated, the land 

 rose and ancient beach ridges and gravel terraces are now found 

 as high as 500 or 600 feet above the present sea level. These ter- 

 raced areas have proven to be valuable sites for settlements and 

 airports, as well as being the most available source of loose, sorted 

 material for road construction. In general, the lands subdued by 

 glacial action have bare rounded hills of broken and frost-riven 

 rocks separated by broad drift-covered coastal plain. 



West of Hudson Bay the terrain of the drift-covered coastal 

 plain is of low relief. The plain is about 50 miles wide at Churchill 

 and broadens to the north, extending inland as far as Yathkyed 

 and Baker Lakes. North of Chesterfield Inlet the land is more 

 rugged, but to the west and east it slopes downward to the broad 

 sandy valley of Back River and the low coast along Roes Welcome 

 Sound. Melville Peninsula is a plateau with an abrupt drop to the 

 west coast and a shelving, terraced slope along the central and 

 northern sections of the east coast. West of the low coastal plain 

 the interior plateau rises to an average altitude of 1,000 feet. 

 Here the rolling surface is marked by rock ridges in a linear ar- 

 rangement with narrow lakes occupying many of the intervening 

 valleys. 



There are countless lakes and streams forming a poorly in- 

 tegrated and undeveloped drainage system, due to the existence of 

 permanently frozen ground which prevents underground drainage, 

 and to the disruptive effects of glaciation. The three main rivers, 

 Kazan, Dubawnt, and Thelon drain toward the northeast across the 

 interior plateau in a general alinement with the bare rocky ridges 

 and flow into Baker Lake and thence to Hudson Bay through 

 Chesterfield Inlet. In many places along their courses they 

 broaden out into lakes. Although these rivers are fairly well 

 mapped as a result of being used as routes of exploration and pene- 

 tration, they are difficult to identify from the air because of the 

 abundance of unmapped rivers and lakes in the area. 



North of Hudson Bay and to the South of Melville Peninsula lies 



43 



