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The lakes that appear in the Knife Lake group of rocks show a similar linear pattern, but the trend is northeast-to-southwest. In the rocks associated with the Ely Greenstone formation, the pattern is less regular and the depressions in the bedrock are not as deep. Thus shallower lakes are found there.

In the area underlain by the Saganaga Granite the story is a little different. Here the shapes of the lakes are dictated by cracks in the Precambrian rock. As the cracks were made wider by erosion, they became linear depressions that lakes could occupy. Many of the lakes lie in collections of linear depressions oriented in more than one direction, so that the lakes have zigzag shapes. An overhead view of the area reveals many jagged lakes interconnected by linear channels. Saganaga Lake itself is a good example.

Because of ice age glaciation and the characteristic Precambrian rock of northeastern Minnesota, the Boundary Waters Canoe Area, with all of its interconnected lakes and streams, is one of the most extraordinary recreational wilderness areas in the world.