Environmental Engineering Reference
In-Depth Information
EURASIAN PLATE
EURASIAN PLATE
NORTH
AMERICAN
PLATE
NORTH
AMERICAN
PLATE
ANATOLIAN
PLATE
ANATOLIAN
PLATE
JUAN DE
FUCA PLATE
JUAN DE
FUCA PLATE
CHINA
SUBPLATE
CHINA
SUBPLATE
CARIBBEAN
PLATE
CARIBBEAN
PLATE
PHILIPPINE
PLATE
PHILIPPINE
PLATE
ARABIAN
PLATE
ARABIAN
PLATE
AFRICAN
PLATE
AFRICAN
PLATE
PACIFIC
PLATE
PACIFIC
PLATE
SOUTH
AMERICAN
PLATE
SOUTH
AMERICAN
PLATE
NAZCA
PLATE
NAZCA
PLATE
INDIA-AUSTRALIAN
PLATE
INDIA-AUSTRALIAN
PLATE
SOMALIAN
SUBPLATE
SOMALIAN
SUBPLATE
ANTARCTIC PLATE
ANTARCTIC PLATE
Convergent plate boundaries
Divergent boundaries
Transform faults
Active Figure 12-4
Natural capital:
the earth's major tectonic plates. These bands correspond to the
patterns for the types of lithospheric plate boundaries shown in Figure 12-5.
See an animation based on
this figure and take a short quiz on the concept.
fracture (fault) in the lithosphere (Figure 12-5, bottom).
Most transform faults are located on the ocean floor
but a few are found on land. For example, the North
American Plate and the Pacific Plate slide and rub
past each other along California's San Andreas fault.
Southern California is slowly moving along this trans-
form fault toward northern California. Perhaps 30 mil-
lion years from now, the geographical area we now
call Los Angeles will probably slowly grind and slide
by the geographical area now known as San Francisco.
In contrast, external processes tend to wear it down
and produce a variety of landforms and environments
due to the buildup of eroded sediment.
One major external process is
erosion:
the process
by which material is dissolved, loosened, or worn
away from one part of the earth's surface and de-
posited elsewhere (Figures 10-8 and 10-9, p. 212). Flow-
ing streams and rain cause the most erosion. Wind
blowing particles of soil from one area to another also
produces erosion. Human activities—particularly
those that destroy vegetation that holds soil in place—
accelerate this external process.
Weathering
consists of the physical, chemical, and
biological processes that break down rocks and miner-
als into smaller particles that can then be eroded.
Three types of weathering processes exist.
The first process is
physical
or
mechanical weather-
ing,
in which a large rock mass is broken into smaller
fragments. It resembles what happens when you ham-
mer a rock into pieces. The most important agent of
mechanical weathering is
frost wedging,
in which water
Science: Geologic Processes
on the Earth's Surface
Water and wind move large amounts of soil and
broken-down pieces of rock from one place to
another.
Geologic changes based directly or indirectly on en-
ergy from the sun and on gravity (rather than on heat
in the earth's interior) are called
external processes.
In-
ternal processes generally build up the earth's surface.
