AP Environmental Science Unit 4

Unit 4: Earth Systems and Resources

1. Plate Tectonics and Earth's Structure

• Earth’s Layers:
  
  

  • Core: Inner (solid) and outer (liquid) core; composed mainly of iron and nickel.

  • Mantle: Semi-solid rock; convection currents drive plate movement.

  • Crust: Outermost layer; divided into continental and oceanic crust.

• Plate Tectonics:
  
  

  • Driven by convection currents in the mantle.

  • Types of Plate Boundaries:

    • Convergent: Plates collide (e.g., mountains, volcanoes, trenches).

    • Divergent: Plates move apart (e.g., mid-ocean ridges, rift valleys).

    • Transform: Plates slide past each other (e.g., earthquakes along fault lines like the San Andreas Fault).

• Earthquake and Volcano Formation:
  
  

  • Occur mainly along plate boundaries.

  • Measured using the Richter Scale for magnitude and Mercalli Scale for intensity.

2. Soil Systems

• Formation of Soil:
  
  

  • Influenced by parent material, climate, organisms, topography, and time.

  • Soil is a mix of minerals, organic matter, air, and water.

• Soil Properties:
  
  

  • Texture: Proportions of sand, silt, and clay.

  • Porosity: Space between particles.

  • Permeability: Ability of water to flow through soil.

• Soil Horizons:
  
  

  • O Horizon: Organic material (leaf litter, decomposed matter).

  • A Horizon: Topsoil; rich in organic material.

  • B Horizon: Subsoil; accumulates nutrients.

  • C Horizon: Weathered parent material.

  • R Horizon: Unweathered bedrock.

• Soil Erosion:
  
  

  • Caused by water, wind, deforestation, and poor agricultural practices.

  • Prevention Methods: Contour farming, terracing, no-till farming, and planting cover crops.

3. Earth's Atmosphere

• Atmospheric Layers:
  
  

  • Troposphere: Weather occurs here; densest layer.

  • Stratosphere: Contains the ozone layer; absorbs UV radiation.

  • Mesosphere: Meteors burn up here.

  • Thermosphere: Contains ionosphere; auroras occur.

  • Exosphere: Outermost layer, merges into space.

• Weather vs. Climate:
  
  

  • Weather: Short-term atmospheric conditions (temperature, humidity, precipitation).

  • Climate: Long-term patterns (e.g., tropical, temperate, polar).

• Coriolis Effect:
  
  

  • Causes deflection of winds and currents due to Earth’s rotation.

  • Results in trade winds, westerlies, and polar easterlies.

4. Watersheds and Water Resources

• Watersheds:
  
  

  • Area of land where all water drains into a common body (river, lake, ocean).

  • Affected by topography, soil type, and land use.

• Groundwater:
  
  

  • Found in aquifers (permeable rock layers).

  • Overuse Issues: Subsidence, saltwater intrusion.

• Human Impact on Water Resources:
  
  

  • Dams, water pollution, over-extraction, and land-use changes.

5. Weathering, Erosion, and Deposition

• Weathering:
  
  

  • Physical: Breaking down of rocks (e.g., frost wedging, thermal expansion).

  • Chemical: Breakdown due to chemical reactions (e.g., acid rain).

  • Biological: Roots and organisms breaking rock.

• Erosion and Deposition:
  
  

  • Erosion moves materials, and deposition lays them down.

  • Caused by water, wind, ice, and gravity.

6. Natural Disruptions to Earth Systems

• Natural Disasters:
  
  

  • Earthquakes, tsunamis, volcanic eruptions, hurricanes, floods, and droughts.

  • Effects: Habitat destruction, loss of biodiversity, soil degradation.

• El Niño and La Niña:
  
  

  • El Niño: Warm water in the Pacific Ocean disrupts global weather patterns (e.g., droughts, floods).

  • La Niña: Cooler-than-normal Pacific waters; opposite weather effects.

7. Sustainability and Resource Use

• Land Use Management:
  
  

  • Sustainable agriculture practices to preserve soil.

  • Urban planning to minimize environmental impact.

• Renewable vs. Nonrenewable Resources:
  
  

  • Importance of managing nonrenewable resources (minerals, fossil fuels).

  • Transition to renewable energy sources (solar, wind, hydro).