Physical Geography of the United States I - Topography & Physiography Study Notes

Why the Physical Environment Matters

• Influence on Human Activity
    - Physical landscapes heavily influence
      - Settlement patterns
      - Transportation routes
      - Agriculture
      - Economic activity

• Regional Identity
    - Reflects physical geography, including:
      - Climate
      - Terrain
      - Vegetation
      - Resources

• Natural Resources
    - Environment provides essential resources such as:
      - Minerals
      - Forests
      - Water
      - Fertile soil

• Environmental Challenges
    - Physical processes can cause environmental issues:
      - Flooding
      - Erosion
      - Earthquakes
      - Drought

• Diversity of Landscapes
    - Different opportunities and limitations for human activity due to varied landscapes.

Key Terminology

• Physiography:
    - Study of Earth’s physical characteristics, patterns, and processes that shape landscapes.

• Landforms:
    - Natural features of the Earth’s surface including:
      - Mountains
      - Valleys
      - Plains
      - Rivers
      - Lakes
      - Coastlines.

• Topography:
    - The physical layout and elevation of landforms in an area
    - Often represented using topographic maps.

Four Major Physiographic Features of the United States

1. Eastern Coastal Plain:
      - Low elevation and flat terrain formed by sediment deposition.
      - Contains wetlands, barrier islands, and estuaries.

2. Embayed Coast:
      - Coastline featuring large indentations forming bays and estuaries.
      - Example: Chesapeake Bay.

3. Eastern Mountains:
      - Includes the Appalachian Mountains and Ozarks.
      - Characterized as older mountains that have experienced significant erosion over time.

4. Interior Plains:
      - Broad region of flat or gently rolling terrain in the center of North America.
      - Known for very fertile soils.

5. Western Mountains:
      - Rugged and geologically active region including the Rocky Mountains and Pacific coastal ranges.

Major Physiographic Processes

• Plate Tectonics:
    - Earth’s lithosphere (rigid crust and upper mantle) is divided into about two dozen large tectonic plates.
    - Plate interaction produces:
      - Earthquakes
      - Volcanoes
      - Mountain building.

• Examples:
    - Cascade Mountains (subduction volcanism)
    - Aleutian Islands (volcanic arc)
    - Hawaii (hotspot volcanism).

• San Andreas Fault:
    - Represents a transform boundary where plates slide past each other.

• Mountain Formation:
    - Appalachian Mountains formed from ancient tectonic collisions.
    - Rocky Mountains formed from tectonic uplift.

Glaciation

• Definition:
    - Movement of large ice sheets across land surfaces.

• Laurentide Ice Sheet:
    - Massive glacier that covered much of Canada and the northern United States during the Pleistocene Ice Age.

• Impact of Glaciation:
    - Glaciers carved valleys, formed the Great Lakes, and deposited fertile soils across the Midwest.
    - Glacial deposits contributed to rolling hills and productive agricultural land.

Erosion Processes

• Fluvial Erosion:
    - Rivers eroding and reshaping landscapes.
    - Example: Canyons.

• Aeolian Erosion:
    - Wind transporting sediment and shaping desert landscapes.

• Coastal Erosion:
    - Ocean waves eroding shorelines and depositing sediments.

• Long-term Processes:
    - Rainfall, wind, and flowing water gradually reshape landforms over extended periods.

Seven Physiographic Landform Regions

1. Southeastern (Gulf–Atlantic) Coastal Plain:
      - Characterized by very flat terrain with:
        - Wetlands
        - Marshes
        - Barrier islands.
      - Embayed coastline with many bays and estuaries.
      - Extends from New England to Florida and west to Texas.

2. Appalachian Uplands & Piedmont:
      - Old, heavily eroded mountain system extending from Alabama to the Gulf of St. Lawrence.
      - Piedmont:
        - Rolling foothill region between the Appalachians and the Coastal Plain.
      - Fall Line:
        - Boundary where rivers drop in elevation from the Piedmont to the Coastal Plain, often creating rapids or waterfalls.
        - Many historic cities developed along the Fall Line.

3. Interior Uplands (Ozark & Ouachita Mountains):
      - A relatively small mountainous region within the generally flat interior plains.
      - Lower elevation and relief compared to the Appalachian Mountains.
      - Located primarily in Arkansas, Missouri, and Oklahoma.

4. Interior Plains / Central Lowlands:
      - A large region of rolling plains located in the interior of the continent.
      - Land formed by glacial deposits during the Ice Age.
      - Recognized as a highly productive agricultural region.

5. Rocky Mountains:
      - Characterized by an abrupt increase in elevation west of the central lowlands.
      - Relatively young mountain system compared to the Appalachians with some of the highest elevations in North America.

6. Intermontane Region:
      - Includes plateau and basin landscapes located between the Rocky Mountains and Pacific Coast ranges.
      - Comprises the Colorado Plateau, Columbia Plateau, and Great Basin.
      - Known for deserts, canyons, and dramatic erosion landscapes.

7. Pacific Coast Region:
      - Located along the Pacific 'Ring of Fire'.
      - Characterized by earthquakes and volcanic activity.
      - Major mountain ranges include:
        - Cascade Range
        - Sierra Nevada
        - Olympic Mountains
        - Alaska Range
        - Chugach Range
        - St. Elias Range.
      - Denali in Alaska is the highest mountain in North America.
      - Important valleys include the Central Valley, Willamette Valley, and Puget Sound region.

Key Takeaways

• Physiographic processes are fundamental in shaping the modern physical landscape of the United States.

• The country consists of four broad physiographic features and seven specific landform regions.

• These physical regions significantly influence human settlement, economic activities, agriculture, and environmental risks.