the great lakes are not only big on top (surface area) but they are very deep too, the shallowest, lake Erie averages about 200 feet deep, and Superior, 1,300 feet deep. the EPA web site-- Sparteye's links above link to it--have lots of details..

or go directly to it
http://www.epa.gov/glnpo/atlas/intro.html


my other obsession