Canal this trend. Yet in other countries canals grew in size as construction techniques improved. During the 19th century in the US, the length of canals grew from to over 4,000, with a complex network making the Great Lakes navigable, in conjunction with Canada, although some canals were later drained and used as railroad rights-of-way. In the United States, navigable canals reached into isolated areas and brought them in touch with the world beyond. By 1825 the Erie Canal, long with 36 locks, opened up a connection from the populated Northeast to the Great Lakes. Settlers flooded into regions serviced by
Great Lakes some higher hills became Great Lakes islands. The Niagara Escarpment follows the contour of the Great Lakes between New York and Wisconsin. Land below the glaciers "rebounded" as it was uncovered. Since the glaciers covered some areas longer than others, this glacial rebound occurred at different rates. A notable modern phenomenon is the formation of ice volcanoes over the lakes during wintertime. Storm-generated waves carve the lakes' ice sheet and create conical mounds through the eruption of water and slush. The process is only well-documented in the Great Lakes, and has been credited with sparing the southern shorelines from worse