Geology Reference
In-Depth Information
Chapter 9
When Crustal Plates Meet, It's
All Relative
In This Chapter
Understanding density
Recognizing two types of crust
Examining the role of density in plate interactions
Defining plate boundaries, relatively
Deforming rocks and building mountains
With the theory of plate tectonics (see Chapter 8), geologists finally had a single explana-
tion that could describe earth processes all around the globe. The relationships among
features that seem so different, such as mountains, earthquakes, and deep sea trenches,
suddenly made a little more sense.
The key to understanding how geologic features and earth processes are related is under-
standing crustal plate movement. The movement of multiple, individual plates of earth's
crust creates and destroys many of the geologic features you are familiar with.
In this chapter, I describe the different types of crust found on the earth's surface, includ-
ing their different compositions and characteristics. I also explain how the many separate
plates that cover the earth move around and what happens when they collide or move
apart. These motions and the relationship between plates create mountains, earthquakes,
ocean trenches, and volcanoes. Finally, one theory to explain them all!
Density Is Key
In order to understand the interactions between crustal plates described in this chapter,
you must first conquer the concept of
density.
