Visualizing Environmental Science

(Marvins-Underground-K-12) #1
298 CHAPTER 12 Mineral and Soil Resources

0
0 1000 2000 3000 kilometers

1000 2000 3000 miles

60 °S

30 °S

0 °

30 °N

60 °N

60 °S

30 °S

0 °

30 °N

60 °N

Nazca
Plate

African
Plate

Eurasian Plate

Indian–Australian Plate

Antarctic Plate

Pacific
Plate

Juan de
Fuca
Plate

North American Plate

South
American
Plate

Caribbean
Plate

Cocos
Plate

San
Andreas
Fault M
id-At
lan
tic

(^) R
gid
e
E
as
Pt
ac
ific
Divergent boundary
Convergent boundary
Transform boundary
Asthenosphere
Lithosphere
Crust
Upper
mantle
Viscous
nickel
Lower mantle
Solid oxides of iron,
magnesium, silicon
Outer core
Liquid iron
Inner core
Solid iron, nickel
a. The Main Layers of Planet Earth.
b. Plates and Plate
Boundary Locations.
There are seven major
independent plates that
move horizontally across
Earth’s surface. Arrows
show the directions
of plate movements.
The three types of
plate boundaries are
explained in Figure 12.2.



  1. Define plate tectonics and explain its
    relationship to earthquakes and volcanic
    eruptions.

  2. Diagram a simplified version of the rock cycle.


Plate Tectonics and the Rock Cycle


LEARNING OBJECTIVES


eology is an essential part of environmental
science. To better understand the environ-
mental effects of humans on mineral and soil
resources, you must first know something
about the geologic properties of Earth’s outer layers.
Earth’s outermost rigid rock layer, the lithosphere,
consists of Earth’s crust—the outermost layer—and the
uppermost part of the mantle. It is composed of seven
large plates, plus a few smaller ones, that float on the
asthenosphere, the region of the mantle where rocks be-
come hot and soft (Figure 12.1). Continents and
landmasses are situated on some
of these plates. As the plates move
across Earth’s surface, the con-
tinents change their relative posi-
tions. Plate tectonics, the study
of the movement of these plates,
explains how most features on Earth’s surface originate.
An area where two plates meet—a plate boundary—
is a site of intense geologic activity (Figure 12.2). Three
types of plate boundaries—divergent, convergent, and
transform—exist; all three types occur both in the ocean
and on land. Two plates move apart at a divergent plate
boundary. When two plates move apart, a ridge of molten
rock from the mantle wells up between them; the ridge
continually expands as the plates move farther apart. The
Atlantic Ocean is growing as a result of the buildup of

G


Earth’s layers and surface
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Which plate do
you live on? Are
you near a plate
boundary?

GLOBAL

LOCAL

plate tectonics
The study of the
processes by which
the lithospheric
plates move over the
asthenosphere.
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