Show Menu

Soils of the World Cheat Sheet by

A brief tour through the most common types of soils, how they're formed, and where they can be found.
science     ecology     geology     geography     soil     biosphere     pedosphere     lithosphere

About soils

Soils can be described as 'the intera­ction between the lithos­phere, hydros­phere, and atmosp­here'. They can be classified in a number of ways- i.e. based on colour, moisture, texture, structure etc.
Soil texture- The relative mixing of primary particles. Most commonly, we assess the levels of sand, silt & clay.
Soil struct­ure- The organi­sation of primary particles into secondary units (called peds). We can describe peds as either prismatic, platy, blocky, or crumb.

Soil fauna

Micro­biota- Micros­copic organisms, e.g. bacteria and nematodes.
Mesof­auna- Soil animals of an interm­ediate size, e.g. spring­tails.
Macro­fauna- Soil animals larger than 2mm, e.g. earthw­orms. Lead to larger pore spaces in the soil.

Factors in soil formation

Temp­era­ture- Rates of chemical reaction, and microbial activity increase with increasing temper­ature. This increases the rate of weathering and decomp­osi­tion.
Clim­ate- Temper­ature and rainfall influence weathering and throug­hflow through soils, leading to the formation of eluvial and illuvial horizons. In polar regions, regolith is weathered by freeze­-thaw.
Orga­nis­ms- Micro, macro, and mesofauna mix organic and mineral material thoughout soils through the process of biotur­bation. Humans also modify soils to meet our demands (usually agricu­ltu­ral).
Topo­gra­phy- Altitude and slope aspect can influence soil temper­atures, which influences rate and extent of weathe­ring.
Parent materi­als- Different parent materials (bedrock types) are more easily weathered than others.
Time- The most important factor in soil format­ion. Eventu­ally, bedrock will be weathered and incorp­orated with organic matter if given enough time. Soils in the tropics are much older than those in temperate regions.

Global soils

Key soil types to note are:
Oxis­ols- highly weathered, deep soils. Red in colour, typical of tropical forests.
Ulti­sols- highly weathered, similar to oxisols. Reddis­h/y­ellow in colour, typical of warm, humid climates.
Arid­iso­ls- very little organic content. Typical of deserts.
Ince­pti­sols- little in the way of horizons, e.g. brown earth.
Geli­sols- containing permaf­rost.
 

A typical soil horizon profile

Common types of soil

Brown Earth- Forms in temperate deciduous woodland. Well-i­nco­rpo­rated organic and mineral material due to biotur­bation by soil fauna; this results in an isotropic soil which is good for agricu­lture. Neutral/ mildly acidic pH.
Podzols (spodo­sol­s)- Form in coniferous woodland due to the presence of acidic needles. This needle litter decomposes and releases organic acids which form complexes with aluminium and iron in the E horizon. These leach down into the B horizon, giving an orange­-brown colour. (See image below).
Gley Soils- Form in anoxic conditions in areas of saturated ground. This saturation allows chemical species to be reduced. If drained, gleys can be effective agricu­ltural soils. Grey in colour.
Peat- Formed by the slow decomp­osition of organic matter under wet or cold condit­ions. Blanket peat is fed by precip­ita­tion, and raised bogs (which form in topogr­aphic hollows) is fed by ground­water running in from the sides.

A podzol soil profile. Note the distinct horizons:

Download the Soils of the World Cheat Sheet

2 Pages
//media.cheatography.com/storage/thumb/leahs-notes_soils-of-the-world.750.jpg

PDF (recommended)

Alternative Downloads

Share This Cheat Sheet!

 

Comments

No comments yet. Add yours below!

Add a Comment

Your Comment

Please enter your name.

    Please enter your email address

      Please enter your Comment.

          Related Cheat Sheets

          More Cheat Sheets by Leahs_Notes

          Meiosis Cheat Sheet