Geology Reference
In-Depth Information
Chapter 8
Adding Up the Evidence for
Plate Tectonics
In This Chapter
Suggesting a supercontinent
Advancing plate tectonics with modern technology
Starting in the 1800s, earth scientists of all different types worked to develop theories ex-
plaining the different geologic phenomena they observed. Some studied volcanoes, earth-
quakes, or mountains. Others asked questions about how the continents or oceans were
created.
As I explain in Chapter 3, starting in the late seventeenth century, some geologists began
to accept that the earth had a long history. (Previously, most people had believed that
the earth was only a few thousand years old.) When that shift in thinking occurred, ex-
planations for geologic processes could incorporate long periods of time to create
change.
But as geologists developed ideas explaining the different geologic features of the earth,
they struggled to explain if, and how, all the geologic phenomena were tied together.
What they lacked was a
unifying theory of geology:
a single theory of geologic processes
that explained all the phenomena they observed.
In modern geology, such a unifying theory exists: the
theory of plate tectonics.
In this
chapter, I describe the development of ideas concerning crustal plate movement, which
form the basis of this theory. I also explain how scientists today are gathering evidence to
further support the theory.
Drifting Apart: Wegener's Idea of Contin-
ental Drift
