1
18
Geography
4. THE NATURAL ENVIRONMENT OF NORTH
AMERICA
4.1. The relief and waters
North America has three very different geographical areas.
❚
The Appalachian Mountains
are ancient and medium height. The sources of rivers
such as the Hudson River are found here.
❚
The Great Plains
occupy the centre of Canada and the United States, from the
Arctic Ocean to the Gulf of Mexico. The most important river is the
Mississippi
(with its tributaries, the Missouri and the Ohio) which flows into the Gulf of Mexico.
The
Mackenzie
River flows into the Arctic Ocean, and the
Yukon
River flows into
the Pacific Ocean. The great glacial ice sheet that once covered the northern half
left numerous lakes, such as the
Great Lakes
(Superior, Michigan, Huron, Erie and
Ontario), Great Bear Lake and Great Slave Lake.
❚
The
Rocky Mountains System
are young mountains formed in the alpine orogeny
5
.
They start with the Alaska mountains (
Mount McKinley
, 6 194 m) and divide into
two ranges: the Coast Range and Sierra Nevada and the Rocky Mountains. The
great
Colorado
River runs between them. In Mexico, there are the
Sierra Madre
Occidental
and the
Sierra Madre Oriental
(with numerous volcanoes, such as the
Orizaba and the Popocatepetl) and the high Mexican plateau in the centre. The two
main rivers are the
Colorado
River and the
Rio Grande
(or Bravo).
Due to its size (extending from the Arctic Circle to Antarctica) and its geological history,
America is often studied as two areas: North America and Central and South America.
Rivers and
lakes
Length/
surface area
Mississippi
5971 km
Mackenzie
4240 km
Yukon
3190 km
Grande
3034 km
Colorado
2333 km
San Lorenzo
1200 km
Lake Superior
82000 km
2
Lake Michigan
58000 km
2
5
orogeny:
geological process of
mountain making
2 500 km
0
1:107 658 000
N
Altitude (metres)
4000
2000-4000
1000-2000
500-1000
200-500
0-200
R
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Appalachian
Mountains
Colorado
Plateau
G
r
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a
t
P
l
a
i
n
s
McKinley
6 194
Peak of Orizaba 5 702
Popocatépetl 5 452
Artic circle
Tropic of Cancer
Hudson
Bay
Gulf
of Mexico
Newfoundland
Greenland
Devon
Baffin
Victoria
Vancouver
Aleutian
Islands
Ellesmere
Labrador
Peninsula
Florida
Peninsula
Nova Scotia
Peninsula
Yucatán
Peninsula
California
Peninsula
A
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AT L A N T I C
O C E A N
A R C T I C O C E A N
Sea of
Labrador
P A C I F I C
O C E A N
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Mackenzie
Yukon
Erie Lake
Ontario Lake
Great Bear
Lake
Great Slave
Lake
Winnipeg
Lake
Lake
Superior
Michigan
Lake
Huron
Lake
Beaufort
Sea
Gulf of
Alaska
Bering
Sea
C
o
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s
t
R
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Great
Basin
Baffin
Bay
S
i
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r
r
a
N
e
v
a
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a
120º W
140º W
100º W
80º W 60º W
40º W
160º W
180º W
80º N
20º N
40º N
60º N
