Geoscience Reference
In-Depth Information
the volcanic island. With the passage of additional time, the
volcano disappears entirely (Figures 19.33c, d), leaving an atoll
reef ring isolated in the ocean. Atolls are particularly common
in the South Pacific Ocean and, like reefs everywhere, are home
to a fascinating and colorful variety of ocean animal species
(Figure 19.34).
longshore deposition, swash/backwash, and wind.
This landform is subdivided into three regions (offshore,
foreshore, backshore) on the basis of water depth and
frequency and nature of submergence.
3.
Sand dunes commonly occur in the lee of beaches
where the supply of sand is high and strong winds fre-
quently blow.
4.
A range of depositional features is associated with the
decreased velocity of the longshore current, including
spits, baymouth bars, and tombolos.
KEY CONCEPTS TO REMEMBER ABOUT
DEPOSITIONAL COASTLINES
5.
A coral reef evolves through the growth of small marine
organisms and can be categorized as a fringing reef,
barrier reef, or atoll.
1.
Depositional coastlines form through the process
of sediment accumulation. A coastline that is ex-
tending outward into a body of water is said to be
prograding.
Human Interactions with
Coastlines
2.
The most familiar coastal depositional feature is the
beach. Sediment is supplied to beaches through
As noted previously, coastlines are a favored place for hu-
man interactions related to economic development, trade,
housing, and recreation. Of the 6 billion people who live
on Earth, approximately 37% (2 billion) live within 100 km
(60 mi) of a major coastline. Nearly 50% live within 200 km
(120 mi) of a shore. To see how these figures compare to the
United States, examine Table 19.1. Overall, nearly 144 mil-
lion people (~53% of the population) live near a coastline.
Almost 63 million people live along the Atlantic Coast in cit-
ies such as New York, Boston, Philadelphia, and Miami.
Another 17.3 million people live along the Gulf Coast
in cities such as Tampa, New Orleans, and Houston.
The Great Lakes region is home to almost 27 million
people who live in cities such as Cleveland, Detroit,
and Chicago. Still another 37 million people reside
along the Pacific Coast, with most living in cities
such as Seattle, Portland, San Francisco, and Los An-
geles.
Given that most people in the United States (and the
world) live fairly close to coastlines, it is important to un-
derstand some of the human impacts in these geomorphically
170° E
Equator
160° E
180°
150° E
Solomon
Islands
Pacific
Ocean
10° S
Tahiti
FIJI
20° S
AUSTRALIA
30° S
Figure 19.34 Coral reefs in the South
Pacific Ocean.
These shallow reefs in
the Solomon Islands are home to a fasci-
nating array of life. Such colorful views are
common in most coral reefs around the
world.
40° S
NEW ZEALAND
U.S. Coastal Population Statistics Reported by the U.S. Department of CommerceT
T A B L E 1 9 . 1
Total U.S.
Atlantic Coast
Gulf of Mexico
Great Lakes
Pacific Coast
Total Coastal
Balance of U.S.
Population in Millions
272.7
62.7
17.3
26.8
37.0
143.9
128.8
Percent of Total U.S. Population
100.0
23.0
6.3
9.8
13.6
52.8
47.2
Source
: U.S. Department of Commerce, Bureau of the Census.
