OCEANS AND LAKES 



261 



in the deeper parts of the ocean, and that they do correspond 

 to the sediments gathering on the continental shelves and in 

 the relatively shallow seas. 



LAKES 



Distribution and origin. Lakes range in size from tiny 

 ponds a few feet across to Lake Superior, between 31,000 and 

 32,000 square miles in extent. They vary in depth from 



I 2 3 M 



FIG. 278. Lakes near Pontiac, Michigan. Illustrates the abundance of 

 lakes in parts of the glaciated region. 



inches to 5618 feet in the deepest part of Lake Baikal, in 

 southern Siberia. Most lakes, however, are rather shallow. 

 While they occur at all altitudes from below sea level to 

 thousands of feet above it (the surface of Lake Titicaca is at 



