Interaction of Earth's Spheres in Soil Formation

Geosphere (Lithosphere)

Provides minerals from weathered rock.

Atmosphere

Supplies gases (oxygen, CO₂, nitrogen) for soil chemistry.

Hydrosphere

Adds water for chemical reactions, transport of nutrients.

Biosphere

Contributes organic material from decomposing plants/animals.

Good Soil

Contains minerals that provide nutrients like iron, calcium, potassium.

Organic Matter

Improves fertility, structure, and moisture retention.

Water & Air

Needed for root respiration, chemical reactions, and microbial life.

Residual Soil

Forms in place, directly from weathered bedrock.

Transported Soil

Moved by wind, water, ice, or gravity before settling (e.g., floodplains, dunes).

Warm, wet climates

Lead to faster weathering and deep soils rich in clay & leached nutrients.

Cool, dry climates

Result in slower weathering and thinner soils with more organic matter accumulation.

Extreme rain (tropical climates)

Produces laterite soils, heavily leached and poor in nutrients.

O-Horizon (Organic Layer)

Contains decomposing leaves, plants, and organisms; dark and nutrient-rich.

A-Horizon (Topsoil)

Mineral-rich layer mixed with organic matter, crucial for plant growth.

E-Horizon (Eluviation/Leaching Layer)

Minerals like iron, aluminum, and clay are leached out by water; lighter in color.

B-Horizon (Subsoil/Accumulation Layer)

Clay, minerals, and nutrients accumulate from the E-horizon; denser and harder than topsoil.

C-Horizon (Weathered Parent Material)

Partially broken-down bedrock with little biological activity.

Parent Material (Bedrock or Unweathered Rock)

The original rock that the soil developed from.

Chemical weathering

Can concentrate valuable minerals, forming ore deposits.

Bauxite

An aluminum ore that forms in tropical climates.

Gold & copper deposits

Can form from hydrothermal solutions.

Soil Erosion

Loss of topsoil reduces fertility and plant growth.

Human activities

Like deforestation, overgrazing, and farming accelerate erosion.

Solutions to soil erosion

Include contour plowing, windbreaks, cover crops, and no-till farming.