Great Lakes region Geography of the Interior United States

freighter entering thunder bay on lake huron

the 3 lakes of middle group stand @ practically same level:

lake michigan
lake huron
lake erie

lake michigan , lake huron connected straits of mackinac mackinac bridge spanning straits. lake huron , lake erie connected st. clair river , detroit river, small lake st. clair between them. land northeast of rivers undergoing slow elevation. niagara river connecting lake erie , lake ontario, fall of 326 feet (99 m) (160 feet (49 m) @ cataract) in 30 miles (48 km), of recent origin, older river have mature valley. original valley thought have connected 2 depressions through niagara escarpment thought have been @ present route of welland canal, , have been filled glacial drift. same true st. lawrence, there may not have been original valley. ontarian river precursor lake ontario thought have drained westward, , st. lawrence drainage have been created subsidence due weight of ice sheet.