Landforms

Dr. Pamela Gore
Georgia Perimeter College

Objectives

  1. List the major landforms in the US.
  2. Tell the main characteristics of each landform.
  3. Explain the structural differences between plains, plateaus, and mountains.
  4. Explain the origins and features of folded, upwarped, volcanic, and fault-block mountains.
  5. Tell how the topography of an area influences its development.
This section addresses the following Georgia QCC standard(s)
  1. Identifies common surface features such as oceans, lakes, mountains on audiovisuals, models, or by direct observation.
  2. Examines how land formations influence development of an area (economic).

Topography = The shape of the earth's surface

The topography is made up of different kinds of landforms. There are three major types of landforms:

  1. Mountains
  2. Plains
  3. Plateau

Mountains are natural landscape features that reach high elevations. They typically have narrow summits and steep sides. Relief is high.

Mountains can form in several ways:

  1. Folded and thrust-faulted mountains - the most common type on land - they originate from compressional stresses folding and faulting the rocks of the Earth's crust
    Includes the Appalachian Mountains, the Canadian Rockies, the Alps, Urals, and the Himalayas.
  2. Fault-block mountains - formed when tensional stresses lead to cracking and faulting of the earth's surface. These mountains are bounded on at least one side by high- (to moderate-) angle normal faults. Includes the Basin and Range Province of the western US (Nevada and portions of surrounding states), the Teton Range of Wyoming, the Sierra Nevada Range of California, and mountains along the East African Rift Valleys
  3. Upwarped mountains - caused by broad arching of the crust, sometimes associated with faults. Includes the Black Hills of South Dakota, the Adirondack Mountains of New York, and parts of the Rocky Mountains.
  4. Volcanic mountains - formed when hot magma from the Earth's interior breaks through the surface of the Earth.
    Includes the volcanic islands of Hawaii, volcanoes on land, as well as the ocean ridge system, which comprises the longest mountain belt on Earth (65,000 km or 40,000 mi).

Plains are flat areas that do not rise far above sea level. They are areas of low relief.
Examples:

  1. Coastal plains (Atlantic Coastal Plain, Gulf Coastal Plain)
  2. Interior plains (Great Plains of the US)

Plateaus are broad, flat areas of land that reach more than 600 m above sea level. They are not considered to be mountains because their surfaces are fairly flat. Plateaus maybe cut deeply by streams, such as the Colorado Plateau, which is cut by the Colorado River, forming the Grand Canyon in Arizona.


Grand Canyon, Arizona

There are many other types of landforms. They can be grouped into eight categories based on their origin:

  1. Landforms due to geologic structures (such as faults, anticlines, structural domes and basins, horizontal layers, etc.)
    Mountains, plains, plateaus, canyons, buttes, mesas.


    Buttes in Monument Valley, Arizona/Utah border

  2. Landforms due to glaciers (cirques, aretes, horns, drumlins, eskers, finger lakes, U-shaped valleys, hanging valleys, kettles, terminal moraines, etc.)

  3. Landforms due to igneous activity (cinder cone, shield volcano, composite cone (or stratovolcano), lava dome volcanoes, caldera, crater, stock, dikes, volcanic neck)

  4. Landforms due to mass movement (landslides, slumps)

  5. Landforms due to running water (drainage patterns, alluvial fans, delta, braided stream, meandering stream, floodplain, abandoned meanders or oxbow lakes, V-shaped valley, etc.)

  6. Landforms due to groundwater (karst topography or sinkholes, disappearing stream, spring, cave)

  7. Landforms due to wind (parabolic dunes, barchan dunes, longitudinal dunes, transverse dunes)

  8. Landforms due to waves and currents (beach, estuary, barrier island, bay, baymouth bar, sand spit, tombolo, marine terraces, sea cave, sea cliff, sea stack, sea arch, headland)


    Sea arch

See examples of many of these landforms in photos at this web site: http://www.athena.ivv.nasa.gov/curric/land/landform/landform.html

See examples of the various types of landforms on topographic maps at this web site: http://www.csus.edu/indiv/s/slaymaker/Geol10L/landforms.htm

Physiographic Provinces

The US can be divided into a number of physiographic provinces based on the types of landforms found there. Click here to see a map of the major physiographic provinces of the US: http://www.gpc.edu/~pgore/geology/historical_lab/scanning/131.jpg.

These include:

  1. Coastal Plain
  2. Piedmont
  3. Blue Ridge
  4. Valley and Ridge
  5. Appalachian Plateau
  6. Interior Lowlands
  7. Great Plains
  8. Rocky Mountains
  9. Colorado Plateau
  10. Basin and Range
  11. Columbia Plateau
  12. Sierra Nevada
  13. Cascades
  14. Coast Ranges
  15. New England
  16. Adirondacks
  17. Superior Upland
  18. Ouachitas
  19. Ozark Plateau

Each has a distinctive topography and geologic history.

Land formations influence the economic development of an area. Note that the major US cities tend to be near bodies of water. They also tend to be in relatively flat areas, such as plains, or in valleys.

Physiographic Provinces of Georgia

Examine the shaded relief map of Georgia at this web address: http://fermi.jhuapl.edu/states/maps1/ga.gif.

Using the map of the physiographic provinces of the US, and looking carefully at the shaded relief map, can you outline and name the FIVE physiographic provinces in Georgia?

Credits: Images on this page are from Microsoft Clip Art Live

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Page created by Pamela J. W. Gore
Georgia Perimeter College,
Clarkston, GA

February 3, 2001