M isso uri R . Mississip p i R . Oh io R. Gulf of Mexico M isso uri R . Mississip p i R . Oh io R. 0 250 500 KILOMETERS0 250 500 MILES0 250 500 KILOMETERS0 250 500 MILES ▲Figure GN 14.1 Map of the Mississippi River basin. 409 GEOSYSTEMSnow The Disappearing Delta Before modern engineering of the chan- nel, the Mississippi River carried over 400 million metric tons of sedi- ment annually to its mouth. River deposits built from this sediment now underlie most of coastal Louisiana. Today, the flow carries less than half its previous sediment load. This decline, combined with land subsidence and sea-level rise, means that the delta region is shrinking in size each year. The tremendous weight of sediment deposition at the Mississip- pi’s mouth has caused the entire delta region to lower as sediments become compacted, a process that is worsened by human activities such as oil and gas extraction. In the past, additions of sediment bal- anced this subsidence, allowing the delta to build. With the onset of human activities such as upstream dam construction, the delta is now subsiding without sediment replenishment. Compounding the problem is the maze of excavated canals through the delta for shipping and oil and gas exploration. As the land surface sinks, these canals allow seawater to flow inland, changing the salinity of inland waters. Freshwater wetlands whose roots help stabilize the land surface during floods are now declining. This makes the delta more vulnerable to flooding from hurricane storm surge, another factor hastening the delta’s demise. Finally, sea-level rise threatens coastal land and wetlands, most of which are less than 1 m (3.2 ft) above sea level. With continued local sea-level rise, lands not protected by levee embankments and other structures that prevent flooding will con- tinue to submerge. In this chapter, we examine the natural pro- cesses by which rivers erode, transport, and de- posit sediment, forming landforms such as deltas. 1. Why are engineers trying to keep the Mississippi River in its present channel? 2. What three factors are causing the Mississippi delta to disappear? Changes on the Mississippi River Delta T he immense Mississippi River basin drains 41% of the continental United States (Figure GN 14.1). From its head- waters in Lake Itasca, Minnesota, the Missis- sippi’s main stem flows southward, collecting water and sediment over hundreds of miles. As the river nears the Gulf of Mexico, the flow energy diminishes and the river depos- its its sediment load. This area of deposition forms the delta, the low-lying plain at the river’s end. Like most rivers, the Mississippi continu- ously changes its channel, seeking the short- est and most efficient course to the ocean. In southern Louisiana, the Mississippi’s chan- nel has—over thousands of years—shifted course across an area encompassing thou- sands of square miles. Throughout this time span, f ...

1. M
isso
uri R
.
Mississip
p
i R
.
Oh
io
R.
Gulf of Mexico
M
isso
uri R
.
Mississip
p
i R
.

2. Oh
io
R.
0
250 500 KILOMETERS0
250 500 MILES0
250 500 KILOMETERS0
250 500 MILES
▲Figure GN 14.1 Map of the Mississippi River basin.
409
GEOSYSTEMSnow
The Disappearing Delta Before modern engineering of the chan-
nel, the Mississippi River carried over 400 million metric tons
of sedi-
ment annually to its mouth. River deposits built from this
sediment
now underlie most of coastal Louisiana. Today, the flow carries
less
than half its previous sediment load. This decline, combined
with
land subsidence and sea-level rise, means that the delta region
is
shrinking in size each year.
The tremendous weight of sediment deposition at the Missi ssip-
pi’s mouth has caused the entire delta region to lower as

3. sediments
become compacted, a process that is worsened by human
activities
such as oil and gas extraction. In the past, additions of sediment
bal-
anced this subsidence, allowing the delta to build. With the
onset
of human activities such as upstream dam construction, the
delta is
now subsiding without sediment replenishment.
Compounding the problem is the maze of excavated canals
through the delta for shipping and oil and gas exploration. As
the
land surface sinks, these canals allow seawater to flow inland,
changing the salinity of inland waters. Freshwater wetlands
whose
roots help stabilize the land surface during floods are now
declining.
This makes the delta more vulnerable to flooding from
hurricane
storm surge, another factor hastening the delta’s demise.
Finally, sea-level rise threatens coastal land and wetlands, most
of which are less than 1 m (3.2 ft) above sea level. With
continued
local sea-level rise, lands not protected by levee embankments
and
other structures that prevent flooding will con-
tinue to submerge.
In this chapter, we examine the natural pro-
cesses by which rivers erode, transport, and de-
posit sediment, forming landforms such as deltas.
1. Why are engineers trying to keep the

4. Mississippi River in its present channel?
2. What three factors are causing the
Mississippi delta to disappear?
Changes on the
Mississippi River Delta
T
he immense Mississippi River basin
drains 41% of the continental United
States (Figure GN 14.1). From its head-
waters in Lake Itasca, Minnesota, the Missis-
sippi’s main stem flows southward, collecting
water and sediment over hundreds of miles.
As the river nears the Gulf of Mexico, the
flow energy diminishes and the river depos-
its its sediment load. This area of deposition
forms the delta, the low-lying plain at the
river’s end.
Like most rivers, the Mississippi continu-
ously changes its channel, seeking the short-
est and most efficient course to the ocean.
In southern Louisiana, the Mississippi’s chan-
nel has—over thousands of years—shifted
course across an area encompassing thou-
sands of square miles. Throughout this time
span, floods caused the river to abandon pre-
vious channels and carve new ones. The Mis-
sissippi River attained its present position about 500 years ago
and
began building the delta we see today (Figure GN 14.2).
Engineering the River Channel Since about 1950, engineers

5. have
worked to keep the Mississippi River in its present channel, a
feat
accomplished by dams, floodgates, and artificial levees (earthen
embankments designed to prevent channel overflow). The U.S.
Army Corps of Engineers built the Old River Control Structure
in
1963 to block the Mississippi River from shifting westward
toward
the Atchafalaya River, which takes a steeper, shorter route to
the
Gulf of Mexico. Such a shift would cause the river to bypass
two
major U.S. ports, Baton Rouge and New Orleans, with negative
eco-
nomic consequences. Despite such measures, the Atchafalaya
delta
is growing even as the rest of the Mississippi’s delta disappears.
0
15 30 KILOMETERS0
15 30 MILES
Mississippi
River
delta
Old River Control
Structure
Atchafalaya River
delta
Atchafalaya

6. River
Gulf of Mexico
M
is
s
is
s
ip
p
i R
i v e r
▲Figure GN 14.2 Mississippi River landscape, southern
Louisiana. Inset photo shows
the Old River Control Auxilliary Structure. NASA/USGS; Inset
photo by Bobbé Christopherson.
Mobile
Field Trip
https://goo.gl/bpcQAU
Mississippi River
Delta
M14_CHRI7119_10_SE_C14.indd 409 06/12/16 1:19 AM
https://goo.gl/bpcQAU

7. 410 Geosystems
Earth’s rivers and waterways form vast arterial net-works that
drain the continents. Even though this volume is only 0.003% of
all freshwater, the work per-
formed by this energetic flow makes it an important natural
agent of landmass denudation. Rivers shape the landscape
by removing the products of weathering, mass movement,
and erosion and transporting them downstream.
Remember from Chapter 8 that hydrology is the sci-
ence of water at and below Earth’s surface. Processes that
are related expressly to streams and rivers are termed
fluvial (from the Latin fluvius, meaning “river”). The
terms river and stream share some overlap in usage. Spe-
cifically, the term river is applied to the trunk or main
stream of the network of tributaries forming a river sys-
tem. Stream is a more general term for water flowing in
a channel and is not necessarily related to size. Fluvial
systems, like all natural systems, have characteristic pro-
cesses and produce recognizable landforms.
The ongoing interaction between erosion, transpor-
tation, and deposition in a river system produces fluvial
landscapes. Erosion in fluvial systems is the process
by which water dislodges, dissolves, or removes weath-
ered surface material. This material is then transported
to new locations, where it is laid down in the process
of deposition. Running water is an important erosional
force; in fact, in desert landscapes it is the most signifi-
cant agent of erosion even though precipitation events
are infrequent. We discuss fluvial processes in arid land-
scapes in Chapter 15.
Rivers also serve society in many ways. They provide
us with essential water supplies; dilute, and transport

8. wastes; provide critical cooling water for industry; and
form critical transportation networks. Throughout his-
tory, civilizations have settled along rivers to farm the fer -
tile soils formed by river deposits. These areas continue to
be important sites of human activity and settlement, plac-
ing lives and property at risk during floods (Figure 14.1).
Drainage Basins
Streams, which come together to form river systems, lie
within drainage basins, the portions of landscape from
which they receive their water. Every stream has its own
drainage basin, or watershed, ranging in size from tiny
to vast. A major drainage basin system is made up of
many smaller drainage basins, each of which gathers and
delivers its runoff and sediment to a larger basin, even-
tually concentrating the volume into the main stream.
Figure 14.2 illustrates the drainage basin of the Amazon
River, from headwaters to the river’s mouth (where the
river meets the ocean). The Amazon carries millions of
tons of sediment through the drainage basin, which is as
large as the Australian continent.
Drainage Divides
In any drainage basin, water initially moves downslope
as overland flow, which takes two forms: It can move as
A flooding river carries not only water but also sediment and
debris. When a river overflows its banks into human develop-
ments, the flow can pick up vehicles and knock houses off their
foundations. As the floodwaters recede, debris such as trees
come
to rest and sediment is deposited over most surfaces, including
the
interiors of houses. In June 2016, flooding in West Virginia
caused

9. extensive damage, 23 fatalities, and left residents cleaning up a
land-
scape of mud.
everydaygeosystems
What kind of damage occurs during a river flood?
◀ Figure 14.1 The aftermath
of flooding along the Elk
River, Clendenin, West
Virginia, in June 2016.
[Ty Wright/Getty Images.]
M14_CHRI7119_10_SE_C14.indd 410 24/11/16 12:10 PM
Chapter 14 River Systems 411
0
200 400 KILOMETERS0
200 400 MILES
Amazon River
basin
Mouth of
Amazon River
Amazon River
PACIFIC
OCEAN

10. ATLANTIC
OCEAN
A
n
d
e
s
M
o
u
n
t a
i n
s
Elevation in m (ft)
250
(820)
0
(0)
750
(2460)
1500
(4920)
3000

11. (9840)
4500
(14,760)
▲Figure 14.2 Amazon River drainage basin and mouth. [NASA
SRTM image by Jesse Allen, University of Maryland, Global
Land
Cover Facility; stream data World Wildlife Fund, HydroSHEDS
project (see http:// hydrosheds.cr.usgs.gov/).]
Interfluves
Drainage divide
Drainage basin
Drainage basin
Drainage divide
Drainage divide
Drainage divide
Valley
Valley
Rill
Gully
Shee
tflow
▶ Figure 14.3 Drainage divides. A drainage

12. divide separates drainage basins.
georeport 14.1 Locating the source of the Amazon
Over the past several centuries, scientists and explorers have
designated at least six different sources as the true beginning of
the Ama-
zon River. In the 1970s, southwest Peru’s Apurímac River was
deemed the longest tributary stream, and in 2000, Lake Ticlla
Cocha on the slopes of
Mount Mismi was named as the Apurimac's source. Then in
2014, a team of kayakers used GPS tracking data and satellite
images to determine that
the Mantaro River, also in southwest Peru, is the longest
upstream extension of the Amazon River. However, the new
claim remains under debate.
sheetflow, a thin film spread over the
ground surface, and it can concentrate
in rills, small-scale grooves in the land-
scape made by the downslope move-
ment of water. Rills may develop into
deeper gullies and then into stream
channels leading to the valley floor.
The high ground that separates
one valley from another and directs
sheetflow is called an interfluve
(Figure 14.3). Ridges act as drainage
divides that define the catchment, or
water-receiving, area of every drain-
age basin; such ridges are the dividing
lines that control into which basin the
surface runoff drains.
M14_CHRI7119_10_SE_C14.indd 411 24/11/16 12:10 PM

13. http://hydrosheds.cr.usgs.gov/).]
412 Geosystems
A special class of drainage divides, continental
divides, separate drainage basins that empty into dif-
ferent bodies of water surrounding a continent (Figure
14.4). For North America, these bodies are the Pacific
Ocean, the Gulf of Mexico, the Atlantic Ocean, Hudson
Bay, and the Arctic Ocean. These divides form water-
resource regions and provide a spatial framework for
water-management planning. In North America, the con-
tinental divide separating the Pacific and Gulf/Atlantic
basins runs the length of the Rocky Mountains, reaching
its highest point in Colorado at the summit of Gray’s Peak
at 4352 m (14,278 ft) elevation (Figure 14.5).
As discussed in Geosystems Now, the great
Mississippi–Missouri–Ohio River system drains 41% of
the continental United States. Within this basin, rain-
fall in northern Pennsylvania feeds hundreds of small
streams that flow into the Allegheny River. At the same
time, rainfall in western Pennsylvania feeds hundreds of
streams that flow into the Monongahela River. The two
rivers then join at Pittsburgh to form the
Ohio River. The Ohio connects with the Mis-
sissippi River, which eventually flows to the
Gulf of Mexico. Each contributing tributary,
large or small, adds its discharge and sedi-
ment load to the larger river. In our example,
sediment weathered and eroded in Pennsyl-
vania is transported thousands of kilometers
and accumulates on the floor of the Gulf

14. of Mexico, where it forms the Mississippi
River delta.
Internal Drainage
The ultimate outlet for most drainage ba-
sins is the ocean. In some regions, however,
stream drainage does not reach the ocean.
Instead, the water leaves the drainage basin
by means of evaporation or subsurface gravi-
tational flow. Such basins are described as
having internal drainage. Regions of inter-
nal drainage occur in Asia, Africa, Australia,
Mexico, and the western United States in
Nevada and Utah (discussed in Chapter 15).
An example within this region is the Hum-
boldt River, which flows westward across
Nevada and eventually disappears into the
Humboldt Sink as a result of evaporation
and seepage losses to groundwater. The area
surrounding Utah’s Great Salt Lake, out-
let for many streams draining the Wasatch
Mountains, also exemplifies internal drain-
age, since its only outlet is evaporation. In-
ternal drainage is also a characteristic of the
Dead Sea region in the Middle East and the
region around the Aral Sea and Caspian Sea
in Asia (Figure 14.6).
Drainage Basins as Open Systems
Drainage basins are open systems. Inputs include pre-
cipitation and the minerals and rocks of the regional
geology. Energy and materials are redistributed as the
stream constantly adjusts to its landscape. System out-
puts of water and sediment disperse through the mouth
of the stream or river into a lake, another stream or river,
or the ocean.

15. Change that occurs in any portion of a drainage basin
can affect the entire system. For example, the building
of a dam not only affects the immediate stream envi-
ronment around the structure, but can also change the
movement of water and sediment for hundreds of miles
downstream. Natural processes such as floods can also
push river systems to thresholds, where banks collapse
or channels change course. Throughout changing condi-
tions, a river system constantly strives for equilibrium
among the interacting variables of discharge, chan-
nel steepness, channel shape, and sediment load, all of
which are discussed in the chapter ahead.
(a) Loveland Pass, Colorado, lies along the continental divide
between the Pacific and Gulf/Atlantic drainage basins.
(b) A backpacker approaches the continental divide at Cutbank
Pass, Glacier National Park, Montana.
▲Figure 14.4 The U.S. Continental Divide, Colorado and
Montana. [(a) Erika
Nusser/Alamy. (b) Design Pics Inc./Alamy.]
M14_CHRI7119_10_SE_C14.indd 412 24/11/16 12:10 PM
Chapter 14 River Systems 413
No
rth
A
tla

16. nti
c
dr
ain
ag
e
Pacific
drainage
Pacific
drainage
Arctic
drainage
Arctic
drainage
Hudson Bay
drainage
Gulf/Atlantic
drainage
Atlantic
drainage
6
0
°N170°E
180°

17. 170°W
160°W
150°W
140°W
110°W 90°W
60°W
50°W
40°W
30°W
20°W
70°E
60
°N
50
°N
40
°N
30°
N
20°N

18. 20°N
30°N
40°N
50°N
70°N
80°N
120°W130°W 80°W
Ar
cti
c
Ci
rcl
e
Tropic of Cancer
Bering
Sea
Gulf of
Alaska
Labrador
Sea
Hudson

19. Bay
Baffin Bay
Beaufort
Sea
Gulf of
Mexico
ARCTIC OCEAN
ATLANTIC
OCEAN
ARCTIC OCEAN
PACIFIC
OCEAN
C
A
L
IF
O
R
N
I A
NELSON

20. LABRADOR–NEWFOUNDLAN
D
TEN
NE
SS
EE
L
O
W
E
R
M
IS
S
IS
S
IP
P
I
U
PP
ER

21. C
OL
OR
AD
OInternal
Drainage
GREAT BASIN
COLUMBIA
FRASER
PACIFIC
COASTAL
YUKON
MACKENZIE
PEACE–
ATHABASCA
KEEWATIN
CHURCHILL
SASKATCHEWAN
ASSINIBOINE–
RED

22. NORTHERN
QUEBEC
GREAT
LAKES
ST.
LAWRENCE
NORTH SLOPE–
GASPÉ
MARITIME
COASTAL
NORTH
ATLANTIC
UPPER
MISSISSIPPI
MISSOURI
OHIO
SOUTH
ATLANTIC–
GULF
ARKANSAS–WHITE–RED
TEXAS–GULFRIO
GRANDE
LOWER

23. COLORADO
ARCTIC COAST AND ISLANDS
0
250 500 KILOMETERS0
250 500 MILES
DRAINAGE BASIN
DISCHARGE
CANADA:
Hudson Bay 682,000 (553)
Atlantic 670,000 (544)
Pacific 602,000 (488)
Arctic 440,000 (356)
Gulf of Mexico 105 (0.9)
UNITED STATES:
Gulf/Atlantic 718 (886,000)
Pacific 334 (412,000)
Atlantic 293 (361,000)
millions acre-feet per year
(millions m3 per year)
millions m3 per year
(millions acre-feet per year)
Continental divides
◀ Figure 14.5 Drainage

24. basins and continental
divides, North America.
Continental divides (red
lines) separate the major
drainage basins that empty
through the United States
into the Pacific Ocean,
Atlantic Ocean, and Gulf
of Mexico, and to the
north, through Canada into
Hudson Bay and the Arctic
Ocean. Subdividing these
major drainage basins are
major river basins. [After U.S.
Geological Survey; The National
Atlas of Canada, 1985,
“Energy, Mines, and Resources
Canada”; and Environment
Canada, Currents of Change—
Inquiry on Federal Water
Policy—Final Report 1986.]
◀ Figure 14.6
Utah’s Great Salt
Lake, part of an
interior drainage
system. [Delphotos/
Alamy.]
M14_CHRI7119_10_SE_C14.indd 413 24/11/16 12:10 PM
414 Geosystems
number and length of channels in a given area reflect the

25. landscape’s regional geology and topography. For exam-
ple, landscapes with underlying materials that are easily
erodible will have a higher drainage density than land-
scapes of more resistant rock.
The drainage pattern is the arrangement of channels
in an area. Distinctive patterns can develop based on a
combination of factors, including
• regional topography and slope inclination,
• variations in rock resistance,
• climate and hydrology, and
• structural controls imposed by the underlying rocks.
Consequently, the drainage pattern of any land area on
Earth is a remarkable visual summary of every geologic
and climatic characteristic of that region.
A familiar pattern is dendritic drainage (Figure
14.7a), a treelike pattern (from the Greek word dendron,
meaning “tree”) similar to that of many natural systems,
such as capillaries in the human circulatory system or
the veins in tree leaves. Energy expenditure in the mov-
ing of water and sediment through this drainage system is
efficient because the total length of the branches is mini -
mized. In landscapes with steep slopes, parallel drainage
may occur (Figure 14.7b). In some landscapes, drainage
patterns alter their characteristics abruptly in response to
slope steepness or rock structure (Figure 14.7c).
Other drainage patterns are closely tied to geo-
logic structure. Around a volcanic mountain or uplifted
dome, a radial drainage pattern results when streams
flow off a central large peak. New Zealand’s Mount Rua-
pehu, an active volcano on the North Island, shows such
a radial drainage pattern (Figure 14.8). In a faulted and

26. (a) Note the drainage channels flowing off the central peak of
Mount Ruapehu,
which last erupted in 2007.
(b) Radial drainage pattern.
◀ Figure 14.8 Radial drainage on Mount
Ruapehu, North Island, New Zealand. This
false-color image of the composite vocano shows
vegetation as red, the crater lake as light blue,
and rocks as brown. [NASA.]
Drainage Patterns
A primary feature of any drainage basin is its drainage
density, determined by dividing the total length of all
stream channels in the basin by the area of the basin. The
(a) Dendritic drainage pattern.
(c) Dendritic and parallel drainage in response to local geology
and
relief in central Montana.
(b) Parallel drainage pattern.
Drainage divide
▲Figure 14.7 Dendritic and parallel drainage patterns. [Bobbé
Christopherson.]
M14_CHRI7119_10_SE_C14.indd 414 24/11/16 12:10 PM
Chapter 14 River Systems 415

27. (a) A rectangular stream pattern develops in areas with
jointed bedrock.
(b) A trellis stream pattern develops in areas where the geologic
structure
is a mix of weak and resistant bedrock (such as in folded
landscapes).
Ridges of
resistant rock
Valleys cut in
less-resistant rock
▲Figure 14.9 Drainage patterns controlled by geologic
structure: rectangular and trellis.
S
u
s
q
u
e
h
a
n
n
a
R

28. iv
e
r
As erosion exposes underlying
rock with a different structure,
the river cuts through ridges
of resistant rock rather than
flowing around them.
Water gap
in the eastern United States and in the folded land-
scapes of south-central Utah. Some landscapes display
a deranged pattern with no clear geometry and no true
stream valley. Examples include the glaciated shield re-
gions of Canada, northern Europe, and some parts of the
U.S. upper Midwest.
Occasionally, drainage patterns occur that seem to
be in conflict with the landscape through which they
flow. For example, a stream may initially develop a
channel in horizontal strata deposited on top of up-
lifted, folded structures. As the stream erodes into the
older folded rock layers, it keeps the original course,
downcutting into the rock in a pattern contrary to the
structure of the older layers. Such a stream is a super-
posed stream, in which a preexisting channel pattern
has been imposed upon older underlying rock struc-
tures (Figure 14.10). For example, Wills Creek, presently
cutting a water gap through Haystack Mountain at Cum-
berland, Maryland, is a superposed stream. A water gap
is a notch or opening cut by a river through a mountain
range and is often an indication that the river is older
than the landscape.

29. ▲Figure 14.10 The Susquehanna River in Pennsylvania, a
superposed stream. The Susquehanna River established its
course
on relatively uniform rock strata that covered more complex
geologic
structure below. Over time, as the landscape eroded, the river
“superposed” its course onto the older structure by cutting
through
the resistant strata. [Landsat-7, NASA.]
WoRkitOut 14.1
Stream Drainage Patterns
Choose among dendritic, parallel, radial, rectangular, trellis,
and
deranged drainage patterns to answer the following questions.
1. Which drainage pattern often occurs in a landscape with a
central mountain peak?
2. Which pattern is prominent in the Amazon River basin in
Figure 14.2?
3. Which pattern often occurs in landscapes of jointed
bedrock?
4. Which pattern occurs in landscapes of folded rock, such as
in southern Utah?
5. Which pattern might be found in the Canadian Shield land-
scape shown in Figure 12.2?
jointed landscape, a rectangular pattern (Figure 14.9a)
directs stream courses in patterns of right-angle turns.
In dipping or folded topography, the trellis drainage

30. pattern develops, influenced by folded rock structures
that vary in resistance to erosion (Figure 14.9b). Paral -
lel structures direct the principal streams, while smaller
dendritic tributary streams are at work on nearby
slopes, joining the main streams at right angles, as in
a plant trellis. Such drainage is seen in the nearly par -
allel mountain folds of the Ridge and Valley Province
M14_CHRI7119_10_SE_C14.indd 415 24/11/16 12:10 PM
HR_Chapter 14.docx
Chapter 14
Presentations to Persuade
We are more easily persuaded, in general, by the reasons that
we ourselves discovers than by those which are given to us by
others.
Pascal
For every sale you miss because you’re too enthusiastic, you
will miss a hundred because you’re not enthusiastic enough.
Zig Ziglar
Getting Started
No doubt there has been a time when you wanted something
from your parents, your supervisor, or your friends, and you
thought about how you were going to present your request. But
do you think about how often people—including people you
have never met and never will meet—want something from you?
When you watch television, advertisements reach out for your
attention, whether you watch them or not. When you use the
Internet, pop-up advertisements often appear. Living in the
United States, and many parts of the world, means that you have
been surrounded, even inundated, by persuasive messages. Mass
media in general and television in particular make a significant

31. impact you will certainly recognize. Consider these facts:
· The average person sees between four hundred and six
hundred ads per day—that is forty million to fifty million by the
time he or she is sixty years old. One of every eleven
commercials has a direct message about beauty.[1]
· By age eighteen, the average American teenager will have
spent more time watching television—25,000 hours—than
learning in a classroom.[2]
· An analysis of music videos found that nearly one-fourth of all
MTV videos portray overt violence, with attractive role models
being aggressors in more than 80 percent of the violent
videos.[3]
· Forty percent of nine- and ten-year-old girls have tried to lose
weight, according to an ongoing study funded by the National
Heart, Lung and Blood Institute. [4]
· A 1996 study found that the amount of time an adolescent
watches soaps, movies, and music videos is associated with
their degree of body dissatisfaction and desire to be thin. [5]
· Identification with television stars (for girls and boys), models
(girls), or athletes (boys) positively correlated with body
dissatisfaction. [6]
· At age thirteen, 53 percent of American girls are “unhappy
with their bodies.” This grows to 78 percent by the time they
reach seventeen. [7]
· By age eighteen, the average American teenager will witness
on television 200,000 acts of violence, including 40,000
murders. [8]
Mass communication contains persuasive messages, often called
propaganda, in narrative form, in stories and even in
presidential speeches. When President Bush made his case for
invading Iraq, his speeches incorporated many of the techniques
we’ll cover in this chapter. Your local city council often
involves dialogue, and persuasive speeches, to determine zoning
issues, resource allocation, and even spending priorities. You
yourself have learned many of the techniques by trial and error

32. and through imitation. If you ever wanted the keys to your
parents’ car for a special occasion, you used the principles of
persuasion to reach your goal.
[1] Raimondo, M. (2010). About-face facts on the
media. About-face. Retrieved fromhttp://www.about-
face.org/r/facts/media.shtml
[2] Ship, J. (2005, December). Entertain. Inspire. Empower.
How to speak a teen’s language, even if you’re not
one. ChangeThis. Retrieved
fromhttp://www.changethis.com/pdf/20.02.TeensLanguage.pdf
[3] DuRant, R. H. (1997). Tobacco and alcohol use behaviors
portrayed in music videos: Content analysis. American Journal
of Public Health, 87, 1131–1135.
[4] Body image and nutrition: Fast facts. (2009). Teen Health
and the Media. Retrieved
from http://depts.washington.edu/thmedia/view.cgi?section=bod
yimage&page=fastfacts
[5] Tiggemann, M., & Pickering, A. S. (1996). Role of
television in adolescent women’s body: Dissatisfaction and
drive for thinness. International Journal of Eating Disorders, 20,
199–203.
[6] Hofschire, L. J., & Greenberg, B. S. (2002). Media’s impact
on adolescent’s body dissatisfaction. In D. Brown, J. R. Steele,
& K. Walsh-Childers (Eds.), Sexual Teens, Sexual Media. NJ:
Lawrence Erlbaum Associates, Inc.
[7] Brumberg, J. J. (1997). The body project: An intimate
history of American girls. New York, NY: Random House.
[8] Huston, A. C., et al. (1992). Big world, small screen: The
role of television in American society. Lincoln: University of
Nebraska Press.
14.1 What Is Persuasion?
LEARNING OBJECTIVES
1. Demonstrate an understanding of the importance of
persuasion.

33. 2. Describe similarities and differences between persuasion and
motivation.
Persuasion is an act or process of presenting arguments to
move, motivate, or change your audience. Aristotle taught that
rhetoric, or the art of public speaking, involves the faculty of
observing in any given case the available means of
persuasion.[1] In the case of President Obama, he may have
appealed to your sense of duty and national values. In
persuading your parents to lend you the car keys, you may have
asked one parent instead of the other, calculating the probable
response of each parent and electing to approach the one who
was more likely to adopt your position (and give you the keys).
Persuasion can be implicit or explicit and can have both
positive and negative effects. In this chapter we’ll discuss the
importance of ethics, as we have in previous chapters, when
presenting your audience with arguments in order to motivate
them to adopt your view, consider your points, or change their
behavior.
Motivation is distinct from persuasion in that it involves the
force, stimulus, or influence to bring about change. Persuasion
is the process, and motivation is the compelling stimulus that
encourages your audience to change their beliefs or behavior, to
adopt your position, or to consider your arguments. Why think
of yourself as fat or thin? Why should you choose to spay or
neuter your pet? Messages about what is beautiful, or what is
the right thing to do in terms of your pet, involve persuasion,
and the motivation compels you to do something.
Another way to relate to motivation also can be drawn from the
mass media. Perhaps you have watched programs like Law and
Order, Cold Case, or CSI where the police detectives have many
of the facts of the case, but they search for motive. They want
to establish motive in the case to provide the proverbial
“missing piece of the puzzle.” They want to know why someone
would act in a certain manner. You’ll be asking your audience

34. to consider your position and provide both persuasive arguments
and motivation for them to contemplate. You may have heard a
speech where the speaker tried to persuade you, tried to
motivate you to change, and you resisted the message. Use this
perspective to your advantage and consider why an audience
should be motivated, and you may find the most compelling
examples or points. Relying on positions like “I believe it, so
you should too,” “Trust me, I know what is right,” or “It’s the
right thing to do” may not be explicitly stated but may be used
with limited effectiveness. Why should the audience believe,
trust, or consider the position “right?” Keep an audience-
centered perspective as you consider your persuasive speech to
increase your effectiveness.
You may think initially that many people in your audience
would naturally support your position in favor of spaying or
neutering your pet. After careful consideration and audience
analysis, however, you may find that people are more divergent
in their views. Some audience members may already agree with
your view, but others may be hostile to the idea for various
reasons. Some people may be neutral on the topic and look to
you to consider the salient arguments. Your audience will have
a range of opinions, attitudes, and beliefs across a range from
hostile to agreement.
Rather than view this speech as a means to get everyone to
agree with you, look at the concept of measurable gain, a
system of assessing the extent to which audience members
respond to a persuasive message. You may reinforce existing
beliefs in the members of the audience that agree with you and
do a fine job of persuasion. You may also get hostile members
of the audience to consider one of your arguments, and move
from a hostile position to one that is more neutral or
ambivalent. The goal in each case is to move the audience
members toward your position. Some change may be small but
measurable, and that is considered gain. The next time a hostile

35. audience member considers the issue, they may be more open to
it. Figure 14.1 "Measurable Gain" is a useful diagram to
illustrate this concept.
Figure 14.1Measurable Gain
Edward Hall[2] also underlines this point when discussing the
importance of context. The situation in which a conversation
occurs provides a lot of meaning and understanding for the
participants in some cultures. In Japan, for example, the
context, such as a business setting, says a great deal about the
conversation and the meaning to the words and expressions
within that context. In the United States, however, the concept
of a workplace or a business meeting is less structured, and the
context offers less meaning and understa nding.
Cultures that value context highly are aptly called high-context
cultures. Those that value context to a lesser degree are called
low-context cultures. These divergent perspectives influence the
process of persuasion and are worthy of your consideration
when planning your speech. If your audience is primarily high-
context, you may be able to rely on many cultural norms as you
proceed, but in a low-context culture, like the United States,
you’ll be expected to provide structure and clearly outline your
position and expectations. This ability to understand motivation
and context is key to good communication, and one that we will
examine throughout this chapter.
[1] Covino, W. A., & Jolliffe, D. A. (1995). Rhetoric: Concepts,
definitions, boundaries. Boston, MA: Allyn & Bacon.
[2] Hall, E. (1966). The hidden dimension. New York, NY:
Doubleday.
14.2 Principles of Persuasion
LEARNING OBJECTIVE
1. Identify and demonstrate how to use six principles of
persuasion.

36. What is the best way to succeed in persuading your listeners?
There is no one “correct” answer, but many experts have studied
persuasion and observed what works and what doesn’t work.
Social psychologist Robert Cialdini[1] offers us six principles
of persuasion that are powerful and effective:
1. Reciprocity
2. Scarcity
3. Authority
4. Commitment and consistency
5. Consensus
6. Liking
You will find these principles both universal and adaptable to a
myriad of contexts and environments. Recognizing when each
principle is in operation will allow you to leverage the inherent
social norms and expectations to your advantage, and enhance
your sales position.
Principle of Reciprocity
Reciprocity is the mutual expectation for exchange of value or
service. In all cultures, when one person gives something, the
receiver is expected to reciprocate, even if only by saying
“thank you.” There is a moment when the giver has power and
influence over the receiver, and if the exchange is dismissed as
irrelevant by the giver the moment is lost. In business this
principle has several applications. If you are in customer
service and go out of your way to meet the customer’s need, you
are appealing to the principle of reciprocity with the knowledge
that all humans perceive the need to reciprocate—in this case,
by increasing the likelihood of making a purchase from you
because you were especially helpful. Reciprocity builds trust
and the relationship develops, reinforcing everything from
personal to brand loyalty. By taking the lead and giving, you
build in a moment where people will feel compelled from social
norms and customs to give back.
Principle of Scarcity

37. You want what you can’t have, and it’s universal. People are
naturally attracted to the exclusive, the rare, the unusual, and
the unique. If they are convinced that they need to act now or it
will disappear, they are motivated to action. Scarcity is the
perception of inadequate supply or a limited resource. For a
sales representative, scarcity may be a key selling point—the
particular car, or theater tickets, or pair of shoes you are
considering may be sold to someone else if you delay making a
decision. By reminding customers not only of what they stand to
gain but also of what they stand to lose, the representative
increases the chances that the customer will make the shift from
contemplation to action and decide to close the sale.
Principle of Authority
Trust is central to the purchase decision. Whom does a customer
turn to? A salesperson may be part of the process, but an
endorsement by an authority holds credibility that no one with a
vested interest can ever attain. Knowledge of a product, field,
trends in the field, and even research can make a salesperson
more effective by the appeal to the principle of authority. It
may seem like extra work to educate your customers, but you
need to reveal your expertise to gain credibility. We can borrow
a measure of credibility by relating what experts have indicated
about a product, service, market, or trend, and our awareness of
competing viewpoints allows us insight that is valuable to the
customer. Reading the manual of a product is not sufficient to
gain expertise—you have to do extra homework. The principal
of authority involves referencing experts and expertise.
Principle of Commitment and Consistency
Oral communication can be slippery in memory. What we said
at one moment or another, unless recorded, can be hard to
recall. Even a handshake, once the symbol of agreement across
almost every culture, has lost some of its symbolic meaning and

38. social regard. In many cultures, the written word holds special
meaning. If we write it down, or if we sign something, we are
more likely to follow through. By extension, even if the
customer won’t be writing anything down, if you do so in front
of them, it can appeal to the principle of commitment and
consistency and bring the social norm of honoring one’s word to
bear at the moment of purchase.
Principle of Consensus
Testimonials, or first person reports on experience with a
product or service, can be highly persuasive. People often look
to each other when making a purchase decision, and the herd
mentality is a powerful force across humanity: if “everybody
else” thinks this product is great, it must be great. We often
choose the path of the herd, particularly when we lack adequate
information. Leverage testimonials from clients to attract more
clients by making them part of your team. The principle of
consensus involves the tendency of the individual to follow the
lead of the group or peers.
Principle of Liking
Safety is the twin of trust as a foundation element for effective
communication. If we feel safe, we are more likely to interact
and communicate. We tend to be attracted to people who
communicate to us that they like us, and who make us feel good
about ourselves. Given a choice, these are the people with
whom we are likely to associate. Physical attractiveness has
long been known to be persuasive, but similarity is also quite
effective. We are drawn to people who are like us, or who we
perceive ourselves to be, and often make those judgments based
on external characteristics like dress, age, sex, race, ethnicity,
and perceptions of socioeconomic status. The principle of liking
involves the perception of safety and belonging in
communication.
[1] Cialdini, R. (1993). Influence. New York, NY: Quill.

39. 14.3 Functions of the Presentation to Persuade
LEARNING OBJECTIVE
1. Identify and demonstrate the effective use of five functions
of speaking to persuade.
What does a presentation to persuade do? There is a range of
functions to consider, and they may overlap or you may
incorporate more than one as you present. We will discuss how
to
· stimulate,
· convince,
· call to action,
· increase consideration, and
· develop tolerance of alternate perspectives.
We will also examine how each of these functions influences
the process of persuasion.
Stimulate
When you focus on stimulation as the goal or operational
function of your speech, you want to reinforce existing beliefs,
intensify them, and bring them to the forefront. Perhaps you’ve
been concerned with global warming for quite some time. Many
people in the audience may not know about the melting polar
ice caps and the loss of significant ice shelves in Antarctica,
including part of the Ross Ice Shelf, an iceberg almost 20 miles
wide and 124 miles long, more than twice the size of Rhode
Island. They may be unaware of how many ice shelves have
broken off, the 6 percent drop in global phytoplankton (the
basis of many food chains), and the effects of the introduction
of fresh water to the oceans. By presenting these facts, you will
reinforce existing beliefs, intensify them, and bring the issue to
the surface. You might consider the foundation of common
ground and commonly held beliefs, and then introduce
information that a mainstream audience may not be aware of
that supports that common ground as a strategy to stimulate.

40. Convince
In a persuasive speech, the goal is to change the attitudes,
beliefs, values, or judgments of your audience. If we look back
at the idea of motive, in this speech the prosecuting attorney
would try to convince the jury members that the defendant is
guilty beyond reasonable doubt. He or she may discuss motive,
present facts, all with the goal to convince the jury to believe or
find that his or her position is true. In the film The Day After
Tomorrow, Dennis Quaid stars as a paleoclimatologist who
unsuccessfully tries to convince the U.S. vice president that a
sudden climate change is about to occur. In the film, much like
real life, the vice president listens to Quaid’s position with his
own bias in mind, listening for only points that reinforce his
point of view while rejecting points that do not.
Audience members will also hold beliefs and are likely to
involve their own personal bias. Your goal is to get them to
agree with your position, so you will need to plan a range of
points and examples to get audience members to consider your
topic. Perhaps you present Dennis Quaid’s argument that loss of
the North Atlantic Current will drastically change our climate,
clearly establishing the problem for the audience. You might
cite the review by a professor, for example, who states in
reputable science magazine that the film’s depiction of a
climate change has a chance of happening, but that the timetable
is more on the order of ten years, not seven days as depicted in
the film. You then describe a range of possible solutions. If the
audience comes to a mental agreement that a problem exists,
they will look to you asking, “What are the options?” Then you
may indicate a solution that is a better alternative,
recommending future action.
Call to Action
In this speech, you are calling your audience to action. You are
stating that it’s not about stimulating interest to reinforce and

41. accentuate beliefs, or convincing an audience of a viewpoint
that you hold, but instead that you want to see your listeners
change their behavior. If you were in sales at Toyota, you might
incorporate our previous example on global warming to
reinforce, and then make a call to action (make a purchase
decision), when presenting the Prius hybrid (gas-electric)
automobile. The economics, even at current gas prices, might
not completely justify the difference in price between a hybrid
and a nonhybrid car. However, if you as the salesperson can
make a convincing argument that choosing a hybrid car is the
right and responsible decision, you may be more likely to get
the customer to act. The persuasive speech that focuses on
action often generates curiosity, clarifies a problem, and as we
have seen, proposes a range of solutions. They key difference
here is there is a clear link to action associated with the
solutions.
Solution
s lead us to considering the goals of action. These goals address
the question, “What do I want the audience to do as a result of
being engaged by my speech?” The goals of action include
adoption, discontinuance, deterrence, and continuance.
Adoption means the speaker wants to persuade the audience to
take on a new way of thinking, or adopt a new idea. Examples
could include buying a new product, voting for a new candidate,
or deciding to donate blood. The key is that the audience
member adopts, or takes on, a new view, action, or habit.

42. Discontinuance involves the speaker persuading the audience to
stop doing something what they have been doing, such as
smoking. Rather than take on a new habit or action, the speaker
is asking the audience member to stop an existing behavior or
idea. As such, discontinuance is in some ways the opposite of
adoption.
Deterrence is a call action that focuses on persuading audience
not to start something if they haven’t already started. Perhaps
many people in the audience have never tried illicit drugs, or
have not gotten behind the wheel of a car while intoxicated. The
goal of action in this case would be to deter, or encourage the
audience members to refrain from starting or initiating the
behavior.
Finally, with continuance, the speaker aims to persuade the
audience to continue doing what they have been doing, such as
reelect a candidate, keep buying product, or staying in school to
get an education.
A speaker may choose to address more than one of these goals
of action, depending on the audience analysis. If the audience is
largely agreeable and supportive, you may find continuance to
be one goal, while adoption is secondary.

43. These goals serve to guide you in the development of solution
steps.