section 1.3

Western Mountains and Deserts

Main Idea

  • The resources of the western United States and Canada are rich in some areas and limited in others.

  • Mountains and high plateaus cover much of the western United States and Canada, creating natural barriers to western coastal regions and offering plentiful resources in various areas.

Landforms and Climate

Cordillera

  • The main landform in the western region is the cordillera.

  • Definition: A cordillera is a system of several mountain ranges that often run parallel to one another.

  • The North American cordillera includes significant ranges:

    • The Rocky Mountains

    • The Sierra Nevadas

The Great Basin

  • In the United States, the area situated between the Rocky Mountains and Sierra Nevada Mountains is known as the Great Basin.

  • Definition: A basin is a depression in the surface of the land.

  • The Great Basin is classified as a desert:

    • Characterized as a dry, often sandy area with minimal rainfall or plant life.

  • This region is marked by:

    • Smaller mountain ranges

    • Canyons (deep, steep-sided valleys formed when rivers cut through soft rock).

  • Notable Canyons:

    • The Grand Canyon: 277 miles in length and up to 18 miles wide, formed over hundreds of millions of years.

Rain Shadow Effect

  • The Great Basin is predominantly dry due to a meteorological phenomenon:

    • Warm, moist air flows east from the Pacific Ocean toward the cordillera's mountains.

    • As this warm air rises up the mountains:

    • It cools

    • Releases moisture on the mountains' western slopes.

    • The resulting air that reaches the eastern lands is dry.

Resources and Conservation

  • Varying climates in the western regions lead to a diverse supply of resources:

    • The Great Basin and surrounding mountain ranges harbor significant mineral deposits.

  • Southwestern Canada:

    • Contains reserves of natural gas, supported by heavy rainfall and numerous lakes providing water power for electricity.

  • Water Issues in Southwestern United States:

    • Shortage of water resources due to rapid population growth in an already dry area.

    • Increased demand for water resources poses a challenge for residents.

    • Dams:

    • A dam acts as a barrier controlling the flow of water, potentially alleviating water shortages.

    • However, dams can also lead to adverse effects:

      • Examples include excess soil erosion.

  • Hoover Dam on the Colorado River:

    • Utilizes water power to supply:

    • Electricity

    • Irrigation

    • Drinking water to parts of Arizona, Nevada, and southern California.

Before You Move On

Inferences

  • The shortage of certain resources can significantly impact the livelihoods and quality of life for residents in the western regions.

Population Density Analysis

Demographic Insights

  • Map Depiction:

    • One dot represents 25,000 individuals.

    • Cities referenced include:

    • San Francisco

    • Seattle

    • Los Angeles

    • Denver

    • Phoenix

  • Map Interpretation Questions:

    1. Describe Geographic Information:

    • Encourage brainstorming descriptive words relating to the photographed landforms and correlate them with lesson content.

    1. Interpret Maps:

    • Identify where population density is at its highest and lowest in the region.

    1. Analyze Visuals:

    • Discuss physical features illustrated in photographs that may explain population distribution in the area.