Geology Reference
In-Depth Information
Chapter 23
Ten (Plus) Ways Humans Act
as Geologic Agents
In This Chapter
Changing water and sediment flows
Mining for coal and over-farming
Drilling for water and moving earth materials
Affecting the climate
Throughout this topic I describe and explain various earth processes and the geologic
features that result. Some scientists have begun to talk about a new period in earth's his-
tory, the
Anthropocene.
They propose that humans, unlike any animals before them, are
shaping and changing the earth in ways that are comparable to the natural processes of
geology. In particular, humans act as surface shapers — shifting rock and sediment
around the earth's surface. But some human activities reach deep into the earth's crust
to extract resources, including water.
In this chapter, I describe for you 11 ways that humans act as geologic agents — ways we
create change that previously only natural, physical processes of the earth could have
created. Perhaps, indeed, the earth is experiencing changes unique to the Anthropocene.
Damming Rivers
Along many of the world's rivers, humans have constructed dams. The dams use the flow
of water to produce electricity. To do so, the natural flow of river water is slowed, creat-
ing a lake on the upriver side of the dam. Water is released through the dam as needed to
produce electricity. The entire process creates a significant deviation from the natural
pattern of streamflow that occurred before the dam was built.
Multiple geologic changes result from dam-building. Slowing the flow of water by building
a dam also slows (or stops) the flow of sediment. Instead of being transported down-
