Lake Superior sits at the system’s headwaters. It is about 350 miles long and 160 miles wide, and it holds enough water to submerge a landmass about the size of North and South America under a foot of water. The lake basin might have been carved by the glaciers, but the 1,300-foot-deep sea is not simply an oversized puddle of ancient ice melt. Lake Superior is a dynamic system, ever filling up with precipitation and stream inflows, and ever flowing out toward the Atlantic.
