Lecture on Soil Formation and Erosion

Introduction

• Lecturer: Mr. Smeeds
• Topic: Soil formation and erosion (AP Environmental Science, Topic 4.2)
• Importance: Foundation for understanding plant growth, water filtration, etc.

Learning Objectives

• Describe characteristics and formation of soil
• Understand soil erosion by wind and water
• Identify research methods for conducting experiments

What is Soil?

• Misunderstood term, often incorrectly referred to as 'dirt'
• Components of Soil:
  • Geological: Sand, silt, clay
  • Organic: Humus (dark, rich organic matter)
  • Nutrients: Ammonium, phosphates, nitrates
  • Water and Air: Fill soil pores, essential for roots
  • Living Organisms: Earthworms, fungi, bacteria

Roles of Soil in Ecosystems

1. Supports Plant Growth
   • Anchor for plant roots
   • Provides water and nutrients (nitrogen, potassium, phosphorus, magnesium)
2. Water Filtration
   • Traps pollutants, cleans water, recharges groundwater
3. Nutrient Recycling
   • Decomposers break down organic matter, replenish soil
4. Habitat
   • Home for earthworms, fungi, bacteria, moles

Weathering vs. Erosion

• Weathering: Breakdown of rocks (physical, chemical, biological)
  • Physical: Wind, rain, freeze-thaw cycles
  • Chemical: Acid rain
  • Biological: Roots breaking rocks
• Erosion: Transport of rock particles
  • Detachment, transport, deposition

Soil Formation

• From Below: Weathering of parent material (bedrock)
  • Breaks down into smaller pieces, forms inorganic part of soil
• From Above: Decomposition of plants and organic matter
  • Contributes humus, nutrients, depth
• Factors affecting Soil Formation:
  • Parent Material: Influences pH, nutrient content
  • Topography: Slope affects erosion and deposition
  • Climate: Temperature and precipitation impact rate
  • Organisms: Decomposers enhance formation

Soil Horizons

1. O Horizon: Organic material, moisture retention
2. A Horizon (Topsoil): Humus, mineral-rich, high biological activity
3. B Horizon (Subsoil): More clay, fewer organics, nutrient presence
4. C Horizon: Least weathered, similar to parent material

Soil Degradation

• Causes:
  • Loss of Topsoil: Tilling, loss of vegetation
  • Compaction: By machinery, livestock, human activity
  • Nutrient Depletion: Repeated farming drains nutrients

Suggested Science Skill

• Design an investigation on climate's effect on soil formation
  • Identify independent and dependent variables

These notes provide an overview and essential details of soil formation and erosion as discussed in the lecture by Mr. Smeeds. Focus on understanding the processes and factors influencing soil dynamics for better environmental science comprehension.