Module 3 Glossary


Step in the nutrient cycle that refers to when nutrients that are released from parent material stay in the soil to be consumed or absorbed by plants and animals.

Acid Rain

Any form of precipitation that has an unusually low pH. Acid rain increases the rate of weathering on materials like rocks and cement.


The build-up of hydrogen in the soil, decreasing the pH of a solution (example of soil transformation). This build up can be from adding in acidic materials or solutions, or removing basic ones.


Process that effects soil formation and refers to adding material into the soil. This could be done through adding food compost to soil or through the weathering of larger rocks.


Refers to how much of a substance is absorbed into a body. The easier the substance is to absorb, the more bioavailable it is. The same element in a different oxidation state will have different bioavailabilities.


The breakdown and mixing of parent material and soil due to plant and animal activities.


The long-term trend in weather. The rate at which soil forms is dependent on the local climate.


Substances that suspended, but not dissolved, in another substance. The colloid and the substance are suspended exist in separate phases (ex. solids floating in liquid).


In the context of TREE and this module, colour refers to the different colour of the soil horizons. Colours give a visual indication of the elements present and the processes acting on the soil.


Decomposition is the process of rotting or decaying, where organic materials break down into simpler materials.


Step in the nutrient cycle that refers to when absorbed nutrients are released, or desorbed, through the exhaling of gases, expelling of solid or liquid waste, or upon a creature’s death and decomposition.


Soil that has been displaced from its native environment in a way that is unusable. Not to be used to refer to soil.


The loss of solid material due to floating on flowing water (example of soil transfer).


The breakdown and movement of soil, rocks, minerals, wood, and man-made materials by wind, water, ice, gravity, and organisms (example of soil removal). Products of erosion do not remain in the same place.


Refers to the water stored within the ground or soil.


In the context of TREE and this module, humans refer to the human activities that impacts the composition and structure of the soil such as industrial and agricultural activities.

Humic Material

Highly decomposed organic material that arises from the decomposition and transformation of plant, animal, and microbial residues.


The loss of dissolved material due to flowing water (example of soil transfer).

Mesic Material

Partially decomposed organic material which contains moderate amounts of moisture.


Refers to any living plant, fungi, animal, insect, and microbe alike. The rate at which soil forms and the composition and structure of the soil are dependent on the organisms inhabiting the soil.

Parent Material

The rocks and sediments in which soil horizons are formed from.


A layer of grass and moss. In terms of soil horizons, peat is part of the organic horizon.


Layer or sphere of Earth the is composed of soil.


Pedoturbation is the breakdown and mixing of parent material and soil.


Permafrost is rock or soil that has been below the freezing point of water, 0° C, for two or more years.


In a geological context, perturbation is a set of processes that alter the soil. The root word is perturb, which means to alter from its original state.


pH stands for the Power of Hydrogen and is a measure of the acidity of a solution. Acidic solutions have pH’s lower than 7, basic solutions have pH’s greater than 7, while neutral solutions have a pH of 7.

Plate Tectonics

A theory describing the large-scale movement of the Earth’s continental and oceanic plates.


The measure of the porous space in a material. It is the ratio between the volume of pores to the total volume. Porous soil allows materials to flow easier, making it susceptible to weathering.


Process that effects soil formation as it that takes material out of the soil. Examples of removal are when someone digs a hole in the ground and removes soil or through the erosion process from wind or water.


Sedimentation is the process of a substance being deposited to form sedimentary rock.

Soil Horizons

Layers of soil parallel to the soil surface whose appearance, structure, and/or composition are distinct from soil horizons above and below.


Substances dissolved in another substance, called the solvent. The solute and solvent exist in the same phase (such as in a liquid).


Refers to the clumping of the textural components. The structure of soil can make it more or less erosion resistant.


The feel, appearance, and consistency of the soil. Soil’s texture is determined by the ratio of mineral components of soil, the ratio between sand, silt, and clay.


One of the soil forming factors. Time, in this context, refers to the duration that parent material, climate, organisms, topography, groundwater, and humans impact soil formation.


Term used to describe the elevation, slope, and orientation of the terrain. The topography of the terrain impacts the rate at which soil forms and the composition and structure of the soil.


Process that effects soil formation where soil materials are moved between locations such as when the ground is broken up (tilling the ground) or through leaching and eluviation of minerals.


Process that effects soil formation and refers to altering the chemical composition of soil materials such as when fertilizer is added to soil or through acidification from acid rain.

Water Table

The depth where the pores in soil become saturated with water.


The breakdown of soil, rocks, minerals, wood, and man-made materials through contact with wind, water, ice and organisms (example of soil addition). Products of weathering remain in the same place.