Teacher's Guide - Soil Formation

Soils can be deep, shallow, new, old, bright orange, black, or even blue (And anywhere in-between)!  What soil looks like depends on the location that it forms in.  It can take over 500 years to form an inch of topsoil on the surface! This lesson is split into three different PowerPoint presentations based on different topics. Soil Formation – Processes details how new soil can appear in a new location, and how soil looks change over time.

Like humans, soils have different properties based on where they are from, and where they “grew up” (formed). Soils have 6 major horizontal layers, or horizons that can be present. These horizons are often present in different types of soil, but each area usually has soils that have similar properties if they are near each other. Soil particles are moved by water, wind, ice, or formed in place from the rocks. Soils form differently for many reasons, and The CLORPT PowerPoint details major soil forming factors: CLimate, Organisms, Relief, Parent material, and Time.

The PowerPoints are appropriate for grades 4+. This presentation is split into three PowerPoints for downloading ease. There are some pretty complex processes that can be discussed at length in older students. Some of the activities listed are for all age groups.

CLORPT

How do soils form? - Processes

How do soils form? - Profiles

Lesson Objectives:

1. Describe what a soil profile looks like?
   • Layers
   • Horizons – O, A, E, B, C
     • All horizons are not always present.  Most typical profile is A-B-C in fields or O-A-B-C in forests.  The R horizon may be very shallow or very deep
2. List the processes that occur in a soil? Give an example of each

• Additions – rain adds water, dust adds minerals, as plants die and animals poop organic mater is added, humans also add fertilizer
• Losses – evaporation, nutrient up take, leaching of nutrients and elements
• Translocations – gravity pull water and dissolved materials down, OM can move in many directions due to critters, clay movement, eluviated horizon
• Transformations – decomposition, weathering, iron rusting (reddening) or dissolving (graying), clay formation
   

3) Describe each horizon?

4) Describe how a soil will change with time.

• OM accumulation

• A horizon forms

• Horizons get thicker

• May get redder if well drained or get grayer if wet

• E horizon becomes more evident

5) Describe a local soil.

Glossary of terms:

In current glossary:

• Decompose

• Bedrock

• Developed Soil

• Eluviated Horizon

• E Horizon

• Horizon

• Humus

• Leaching

• Minerals

• Organic Matter

• Organisms

• Parent material

• Soil

• Soil Profile

• Subsoil

• Topsoil

• Transform

• Weathering

Other glossary words:

• Additions – to add material or substance to the soil

• Losses – to remove material or substance from the soil

• Translocation – to move material or substance within the soil without adding or removing anything

• A Horizon – topsoil, mineral soil horizon with enough OM to make it appear darker (blacker or browner than horizons below it)

• B Horizon – subsoil, zone of accumulation of material from above due to leaching or eluviation

• C Horizon – a horizon composed of material that the soil has formed from

• R Horizon – solid rock, bedrock

• O Horizon – a horizon rich in organic mater

• Soil Monolith – a physical representation (model) of a soil profile

Activities or information:

1) General Soils:

• Lesson Plans -Soil Society of America  (All Grades)  Good background with links to other areas

• Educational Links - USDA NRCS  (Grades K-6) This page lists several other links for additional information from USDA-NRCS.  Includes some basic information and appropriate for lower grades

2)Soil profile photos and description:

• State Soils Booklets (All Grades) This has information and booklets for all of the state soils. Also includes an activity.

• Soil Horizons (Grades 4+) Provides an overview of the soil profile.

• New England Soil Horizons  (Grades 4+, perhaps more towards 8-12) A PowerPoint presentation can be followed from this site.  Good overview for upper levels.  Focuses on New England profiles but can be used in other areas

3)Soil formation:

• Soil Formation and Classification  (Grades 8+) USDA-NRCS discussion of soil forming factors (CLORPT).  Part of web page deals with soil taxonomy which is too advanced for K-8.

• New England Soil Genesis (Grades 4+, perhaps more towards 8-12) A PowerPoint presentation can be followed from this site.  It is a bit advance for 4^th grade but could be used by the teacher for additional information and some examples.  It focuses on the New England region but some of the information is general enough to be used in other areas.

• Soil Mini Monoliths (Grades 4+)  A description of how to make soil profile cards (mini-monoliths) is provided.  This exercise works best with very dry, ground (pulverized) soil materials.  It is difficult to get good results it the soil material is sandy (or sand sized) as the tape is not sticky enough to hold the sand.

Study Questions:

1) How long does it take an inch of soil to form?

• It may take hundreds to thousands of years.  It will take longer in colder and drier regions than in warmer and wetter regions.  This is due to the soil forming processes such as translocation and transformation being slower in cold and/or dry areas. Essentially, chemical reactions (weathering) occur faster as temperature increases.  Since soil formation also requires organisms and organisms require water, reactions (formation) occur faster if there is sufficient water present. 

2) Define the following:

• Losses

• Additions

• Translocations

• Transformations

3) Give example of the following:

• Additions

  • rain adds water, dust adds minerals, as plants die and animals poop organic mater is added, humans also add fertilizer

• Losses

  • evaporation, nutrient up take, leaching of nutrients and elements

• Translocations 

  • gravity pull water and dissolved materials down, OM can move in many directions due to critters, clay movement, eluviated horizon

• Transformations 

  • decomposition, weathering, iron rusting (reddening) or dissolving (graying), clay formation

4) Draw a young soil profile, medium age and older profile.

Questions or feedback about this lesson?  Just contact us.