Geology Reference
In-Depth Information
Chapter 12
Water: Above and Below
Ground
In This Chapter
Cycling around the earth
Carrying sediments in streams
Eroding channels and seeking equilibrium
Marking earth's surface with erosion and deposition
Flowing beneath the surface: Groundwater
Water is all around us. Most obviously, water is in the oceans — 97 percent of earth's wa-
ter is stored in them — but it's also in lakes, rivers, streams and glaciers. It flows over
ground and underground, and it falls from the sky.
Flowing water is a powerful agent of change on earth's surface. As water moves over and
through earth's crust, it picks up rocks and sediment particles, carries them far away, and
leaves them somewhere else.
In this chapter, I explain the details of how flowing water on continents acts as a geologic
agent. (I cover frozen water — ice and glaciers — in Chapter 13 and ocean wave move-
ments in Chapter 15.) I begin by describing the cycling of water through oceans, air, and
continents. I explain how flowing water generates enough energy to transport rocks and
other earth materials, as well as the features of the landscape created by flowing water.
Finally, I describe how water flows underground, creates caves, and becomes heated by
earth's internal energy.
Hydrologic Cycling
The amount of water on earth has been pretty much the same for the last billion years.
Water molecules move among the earth's atmosphere, surface, and underground — and
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