Chapter II: Soil Formation and Its Factors – Vocabulary Review

A set of vocabulary flashcards summarizing key terms and definitions related to soil formation, soil-forming processes, factors, horizons, and parent materials from Chapter II lecture notes.

Acronym for Climate, Living organisms, Relief/topography, Parent material, and Time—the five primary factors that interact to produce soil.

Soil-forming Factors (CLORPT)

The overall process by which true soil develops from unconsolidated parent material, including both parent-material creation and soil-layer evolution.

Soil Formation

Changes in a soil profile caused by leaching, translocation of colloids, organic-matter accumulation, and continued rock and mineral weathering.

Soil Development

A vertical section of soil that displays all of its horizons from the surface down to unweathered material.

Soil Profile

An individual, roughly parallel layer within a soil profile that differs in physical, chemical, or biological properties from layers above or below it.

Soil Horizon

The process by which distinct soil horizons form through gains, losses, transformations, and translocations over time.

Horizonation

Inputs to soil such as organic matter, precipitation water, atmospheric gases (O₂, CO₂), and nutrients (N, Cl, S).

Gains / Additions

Removal of soil constituents—including soluble salts, water (evaporation), N (denitrification), C (as CO₂), soil particles (erosion), and energy (radiation).

Losses

Chemical or physical changes within soil, including mineral weathering, particle-size reduction, formation of secondary minerals, and clay–organic reactions.

Transformations

Movement of mineral and organic materials within soil—e.g., clay, humus, iron oxides, salts—usually from topsoil to subsoil via water, plants, or animals.

Translocation

The unconsolidated mineral or organic matter (upper regolith) from which soil forms; determines initial mineralogy and nutrient status.

Parent Material

All unconsolidated material above bedrock; its upper portion acts as the parent material for soil.

Regolith

Weathered rock and minerals that remain in place at the site of the original bedrock.

Residual (Sedentary) Parent Material

Unconsolidated material moved from its source and deposited elsewhere by water, gravity, wind, ice, or lakes.

Transported Parent Material

Parent material transported and laid down by flowing rivers or streams.

Alluvial Deposits

Parent material moved downslope by gravity, often containing coarse gravel and rock fragments.

Colluvial Deposits

Fine-textured sediments (clay, silt) deposited in lake bottoms.

Lacustrine Deposits

Wind-transported parent material such as loess (silt), dune sand, or volcanic ash.

Eolian Deposits

Sediments laid down on sea or ocean floors, later uplifted or exposed to form soil.

Marine Deposits

Material carried and left by glacial ice, including till, outwash, and moraines.

Glacial Deposits

The shape and slope of the land surface; influences runoff, erosion, drainage, and therefore soil formation speed and depth.

Relief / Topography

Climate and living organisms—so-called because they most strongly drive the rate and degree of soil formation.

Active Factors

Very young soil consisting mainly of unweathered parent material with minimal horizon development.

Embryonic Soil (C Horizon Stage)

Soil that has developed an A horizon above the C horizon; clay formation has just begun.

Young Soil (A over C)

Soil where resistant minerals like quartz dominate, clay content is high, 1:1 clays exceed 2:1 clays, and sesquioxides of Al and Fe are abundant.

Old Soil

Extremely weathered soil with processes nearly halted; dominated by colloidal 1:1 clays and very fine particles (<0.002 mm).

Very Old Soil

Oxides and hydroxides of iron (Fe) and aluminum (Al) that accumulate in highly weathered old soils.

Sesquioxides

Minerals unchanged from the original igneous or metamorphic rock (e.g., quartz, feldspars, biotite).

Primary Minerals

New minerals formed by weathering of primary minerals, such as clays and iron/aluminum oxides.

Secondary Minerals