In order to understand how humans and streams can safely and economically coexist, you need to understand how a stream functions. In this module, we’ll examine geologic time and stream formation, stream terminology, and stream measurement.
Geologic Time and Stream Formation
A map showing the possible location of the ancient Teays River. Parts
of the Wabash River in Indiana follow ancient river systems like the Teays.
Prior to the receding of glaciers, the river systems of the U.S. where in very different locations. (Ohio Department of Natural Resources).As a surprise to you, rivers are alive! Over geologic time new rivers form and old rivers die out. Within Indiana, many of the major streams have changed position over the last 100,000 years due glaciers reshaping how water drains. In recent geologic history, a major river (geologists call it the Teays River) the size of the Ohio River flowed across northwest Indiana. But the river disappeared after the last ice age. On the other hand, glaciers turned the Ohio River from a small stream into the major stream it is today. The geologic processes of glaciers, erosion, mountain building, and plate tectonics slowly alter the course of rivers over geologic time. Parts of the Colorado River haven’t moved for millions of years, yet parts of the Mississippi River have moved in the past 100 years (and continue to move).