APES Unit 4 Review

Plate Tectonics (Topic 4.1)

  • Definition: Tectonic plates are large slabs of the lithosphere floating on the mantle, which is molten rock.

  • Core Composition: Earth’s core is primarily nickel, iron, and radioactive elements, generating heat to keep the mantle liquid.

Types of Plate Boundaries

  1. Divergent Boundaries

    • Plates move away from each other.

    • Results in seafloor spreading, creating mid-ocean ridges.

  2. Convergent Boundaries

    • Plates collide; typically an oceanic plate is subducted under a continental plate.

    • Leads to:

      • Formation of volcanic mountain ranges

      • Creation of trenches at subduction zones.

  3. Transform Boundaries

    • Plates slide past each other.

    • Commonly associated with earthquakes due to friction and locking of plates.

Soil Formation and Characteristics (Topics 4.2 & 4.3)

  • Definition: Soil is more than dirt; it’s a complex mixture of minerals, organic material, air, and water.

  • Components: Includes sand, silt, clay, and organic matter.

Formation Process

  • Weathering of rocks leads to soil creation.

  • Soil consists of different layers:

    • O Horizon: Organic matter, decomposers, plant roots.

    • A Horizon (Topsoil): Nutrient-rich; critical for plant growth.

    • B Horizon (Subsoil): Minimal organic material; contains nutrients like nitrogen and phosphorus.

    • C Horizon: Parent material, minimally weathered.

Weathering vs. Erosion

  • Weathering: Breakdown of rocks into smaller pieces.

  • Erosion: Movement of these particles by natural forces like wind and water.

  • Erosion can deplete topsoil, removing nutrients and microorganisms vital for plant health.

Soil Properties

  • Soil Texture: Ratio of sand, silt, and clay.

    • Affects permeability and water-holding capacity.

  • Soil pH: Affects nutrient availability.

    • Acidic soils have lower nutrient levels and may harm plant roots due to solubility of toxic metals like aluminum.

Fertility Factors

  • Soil fertility depends on chemical and physical properties:

    • Nutrient levels, pH, texture, and moisture retention capabilities all influence its ability to support plant growth.

Atmosphere and Weather Patterns (Topics 4.4 - 4.6)

  • Composition: Predominantly nitrogen (78%), oxygen (21%), and trace gases (0.4%).

  • Layers of the Atmosphere:

    1. Troposphere: Weather occurs here, air we breathe.

    2. Stratosphere: Ozone layer protects us from UV radiation.

    3. Mesosphere: Middle layer, gas density decreases.

    4. Thermosphere: Hottest layer; conditions for auroras.

    5. Exosphere: Outermost layer, merging with space.

  • Wind Patterns:

    • Warm air rises, cools, and condenses, forming pressure systems.

    • Example: Hadley Cell impacts rainfall patterns, leading to deserts at 30° latitude.

Geography's Influence on Climate (Topics 4.7 - 4.8)

  • Seasonal Changes: Result from Earth’s axial tilt (23.5°) and its position around the sun.

    • Equinoxes and solstices mark key seasonal transitions.

  • Proximity to Water & Mountains:

    • Winds carry moisture from water bodies, affecting precipitation patterns.

    • Rain Shadow Effect: Mountains block moisture, creating dry conditions on the leeward side (e.g., Sierra Nevada).

Ocean Phenomena: El Niño and La Niña (Topic 4.9)

  • El Niño: Weakening of trade winds leads to warm water pooling along South America.

    • Results in flooding and disrupted fishing due to reduced upwelling.

  • La Niña: Stronger trade winds push warm water west, causing droughts in South America but enhancing fisheries.

Conclusion

  • Unit 4 elaborates on crucial Earth science concepts, preparing for more advanced topics ahead in the APES curriculum.