Download Major Landforms - iMater Charter Middle/High School

The ways in which people live and work in the United States are affected by the land, water, and weather in their
regions.
Major Landforms
SS.7.G.2.2, SS.7.G.2.3, LA.7.1.6.1
What are the major landforms of the United States?
Think about the landscape of your community. Is it flat or hilly? Is it prairie land or wooded? Are there mountains on
the horizon?
The United States is a vast place with a rich and varied landscape. Many types of landforms are found throughout the
country. A landform is a natural feature on the Earth’s surface. Earth has two general types of land—lowlands and
highlands.
Lowlands
Lowlands are areas of flat land at or near sea level. The central United States has two large lowland areas. The
eastern central lowlands reach west from the Appalachian Mountains to the Mississippi River. Fertile soil makes this
a good farming area.
The western central lowlands are the Great Plains. Plains are large areas of flat land with few trees. The Great Plains
begin west of the Mississippi River and extend from the Canadian to the Mexican border. They gradually rise in
elevation from east to west. The Great Plains are mostly prairie, or rolling grassland, with rich soil. Farmers raise
wheat and cattle in this region.
Lowlands also run along the Atlantic and Gulf coasts. These broad bands of rich land are wider along the Gulf of
Mexico. The Atlantic coastal plains turn from grasslands to woodlands as they move east. In the southeast,
woodlands give way to wetlands. A wetland is a large area of moist land, often covered with a shallow layer of water.
Swamps and marshes are types of wetlands.
Florida’s Everglades are the largest wetland system in the country. The Everglades are actually a wide, shallow,
slowmoving river that covers more than 4,000 square miles. It stretches from Lake Okeechobee in south central
Florida to the Gulf of Mexico. Its marshes are home to thousands of unique plants and animals.
Coastal islands lie along the Atlantic and Gulf coasts. Florida’s Gulf coast is dotted with tiny islands. Its Atlantic coast
has sandbars and barrier islands. The Florida Keys are a series of islands located south of Florida. A special road
called a causeway links them to the mainland.
Busy port cities are an important human-made feature on the coastal plains. Examples of such cities include New
Orleans, Louisiana, and Miami, Florida. These ports help build local economies.
Highlands
In addition to lowlands, the United States has highland regions. These are areas where the land is elevated much
above sea level. West of the Great Plains, highlands extend north and south along much of the length of North
America. The Rocky Mountains, the longest mountain range on the continent, extend 3,000 miles (4,800 km) from
Alaska to Mexico.
Near the Pacific coast are several smaller mountain ranges, which include the Sierra Nevada, the Cascade Range,
the Coast Ranges, and the Alaska Range. Between the Pacific ranges and the Rocky Mountains are the Colorado
Plateau and the Columbia Plateau. A plateau is a large area of flat highland. Pockets of dry lowlands—the Great
Basin, the Mojave Desert, and Death Valley—are located among the highlands. This area is also home to the Grand
Canyon, one of North America’s most distinct, or notably different, physical features. A canyon is a deep valley with
steep rock sides created by a river.
Highland areas are also found in the eastern part of the country. In Arkansas and Missouri, the forested Ozark
Plateau rises out of the surrounding plains. Farther east, the oldest mountain range on the continent—the
Appalachian Mountains—stretches more than 2,000 miles (3,200 km) from eastern Canada to Alabama. Many
smaller ranges, such as the Blue Ridge and White Mountains, make up this chain. Over time, erosion has worn down
the Appalachians, creating rounded peaks.
Classifying What lowland features are found among the highland areas of the country?
Why It MATTERS
Preserving Local Resources
Preserving natural resources helps maintain the beauty and balance of nature in an area. For many years, the Florida
Everglades area suffered as a result of attempts to drain it. Many people have fought to preserve the Florida Everglades.
You can also have a hand in preserving natural resources. Think about a natural resource in your area, such as a lake, a
river, or a nature preserve.
What can you do to help preserve it?
SS.7.G.2.3
Major Waterways
SS.7.G.1.3, SS.7.G.2.2, SS.7.G.2.3
What important waterways are found in the United States?
Bodies of water have played an important role in U.S. history. The Pacific and Atlantic Oceans connected the United States
to Europe and Asia. Waves of people crossed these oceans to settle here. Many settled along the coasts near natural
harbors, spurring the growth of America’s great ocean port cities. Within the country, rivers and lakes have been used for
transportation, irrigation, and varied economic activities. Communities that early settlers built along these waterways later
became key inland port cities.
Rivers
The Mississippi River is the longest river in the United States. It begins at Lake Itasca in Minnesota. It flows south 2,350
miles (3,780 km) into the Gulf of Mexico. Its major tributaries are the Ohio River, the Tennessee River, and the Missouri
River. A tributary is a stream or small river that feeds into a larger river. The Mississippi and its tributaries have made
possible the settlement and economic development of much of the nation. Today, ships travel this water highway, moving
products from inland port cities to foreign ports.
Other waterways support human, animal, and plant life in the eastern United States. The Potomac River flows through the
District of Columbia to Chesapeake Bay. The Hudson River flows south from the Adirondack Mountains to New York City.
The Columbia River is the largest river flowing to the Pacific Ocean. Its key tributary is the Snake River. In the dry
Southwest, the Colorado River is a main source of freshwater. Because dams and irrigation projects have drained the river,
little water empties into the Gulf of California.
Lakes
The Great Lakes are among the largest freshwater lakes in the world. Lakes Superior, Michigan, Huron, Erie, and Ontario
cover more than 94,000 square miles . They supply water to Americans and Canadians. The chain of lakes flows into the St.
Lawrence River, which empties into the Atlantic Ocean. The St. Lawrence Seaway, a joint project of Canada and the United
States, expanded the Great Lakes shipping route. The seaway includes a series of canals, or human-made waterways.
Through it, ships carry goods from Great Lakes cities, such as Chicago and Detroit, to the world.
Lake Michigan also links with the Mississippi River through the Chicago River, a canal system, and the Illinois River. This
system forms one of the largest inland waterways in the world. It enables travel from the northern Atlantic Ocean across the
eastern United States to the Gulf of Mexico.
Another key U.S. lake is the Great Salt Lake in northern Utah. The lake is salty because it does not have an outlet. Three
rivers bring in small amounts of salt that are dissolved in their freshwater. Once in the Great Salt Lake, much of the water
evaporates, leaving the salt behind. This lake is the largest inland body of salt water in the Western Hemisphere.
Many states have lake systems that provide water, fish, and recreation. Florida has thousands of lakes. Lake Okeechobee in
south central Florida is the state’s largest lake. It is the nation’s seventh-largest freshwater lake.
Intracoastal Waterways
The Atlantic Intracoastal Waterway runs more than 1,000 miles (1,600 km) from Norfolk, Virginia, to Miami, Florida. Humanmade canals connect with natural waterways to provide this interior route. Both commercial and recreational boats use it.
Synthesizing What bodies of water form one of the largest inland waterways in the world?
Florida CONNECTION
Lake Okeechobee
To prevent flooding and loss of life, human-made structures such as dikes have been erected around waterways, including Lake
Okeechobee. In 1928 much of the dike around the lake was destroyed by a hurricane with winds of more than 125 miles per hour.
Water from the overflowing lake flooded nearby towns, sweeping away houses and people. Some 2,000 people were killed. It was
called one of the worst natural disasters in U.S. history. Today, area residents are concerned about the aging dike. SS.7.G.2.3
Climate
SS.7.G.2.2, SS.7.G.2.3, LA.7.1.7.3
How does climate vary throughout the United States?
Climate is the pattern of weather that a place experiences over a long period of time. A number of factors help determine
climate, including elevation, nearby bodies of water, and distance from the Equator. Generally, the climate is warmer near
the Equator.
The climate in the United States varies because the country is so big. The climate is affected by two oceans, many different
landforms and waterways, and varying distances from the Equator.
Temperate Zones
Most regions of the United States have a temperate climate. This means there are few extremes in temperature and
precipitation. Precipitation is water that falls to the ground in the form of rain or snow. The southeastern United States has a
humid, subtropical climate. This area receives moderate to plentiful rainfall throughout the year and is generally warm to hot
and humid in the summer. Winters are mild, with limited snowfall.
Much of the United States, extending from New England to the Great Lakes and the Midwest, has a humid continental
climate, with cool, wet weather. Winters are cold, with snowfall, and summer temperatures are mild. Temperatures decrease
and snowfall increases as you move north through this zone.
The weather along the West Coast, from Washington to central California, is affected by moist winds from the Pacific Ocean.
This region has a marine climate. It is warmer in winter there than in the Northeast. It has moderate temperatures for much
of the year and a great deal of rainfall. Southern California has a Mediterranean climate of warm, dry summers and mild,
rainy winters.
Extremes
While most of the United States has a temperate climate, a few states have extreme climates. Much of Alaska has a
subarctic climate. The weather is cold most of the year, with large amounts of snowfall. The summers are short and cool.
Hawaii and southern Florida have tropical climates. The weather is warm or hot most of the year, and there is a great deal of
rainfall. During the rainy season in the latter part of the year, there is a risk of tropical storms and hurricanes.
Much of the West and Southwest has a semiarid steppe climate. Some areas have a midlatitude desert climate. These
climates are very dry, with little rain or snowfall, and tend to be warm to hot during the daytime for much of the year. Desert
areas can become quite cold at night, however.
The Rocky Mountains have a highland climate. High altitudes cause temperature extremes and much precipitation. The
higher a place is above sea level, the colder it is. The mountains stay cooler in the summer and are cold in the winter, with
heavy snowfall. Moisture cools as it rises over the mountains and then falls as it passes over a range. The Continental
Divide runs through these mountains, separating rivers that flow to the east from those that flow to the west.