Which of the following is NOT true about rivers?

A) major rivers, like the upper Mississippi near the Great Lakes, must be relatively old rivers
B) the boundary between hard rocks and soft rocks can be marked by waterfalls
C) loading and unloading of the crust by ice sheets can change the direction rivers flow
D) different parts of a river can be different ages

Upper Mississippi

Refers to the portion of the Mississippi River that flows from its headwaters to the confluence with the Missouri River.

Hard Rocks

Earth materials, such as granite and basalt, that are solid, tough, and resistant to weathering and erosion.

Ice Sheets

Large masses of glacial ice and snow that cover vast areas of land, such as those found in Antarctica and Greenland.