This range of hills is part of the Giants Range Batholith, a large body of rock measuring many miles across. Hundreds of thousands of years ago volcanoes darkened the skies of northeastern Minnesota. The batholith is a result of melted volcanic rock that cooled underground. The rock was exposed by thousands of years of uplift and erosion. The various pink, gray and black colors are due to the different minerals that make up the rock types. Feldspar (pink and white), quartz (gray), biotite and hornblende (black) are some of the minerals you may see.
The Laurentian Divide separates the watershed of streams that flow north to the Arctic Ocean from the watershed of streams that flow south through the Great Lakes to the Atlantic Ocean. Streams on the north slope of the divide flow through Canada to Hudson Bay. Streams on the south slope flow into Lake Superior and the Atlantic, or into the Mississippi River and the Gulf of Mexico.