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Starting Point-Teaching Entry Level Geoscience > Field Labs > Field Lab Examples > Making a Soil Monolith
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Making a Soil Monolith

Aleshia Mueller, Carleton College
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This material is replicated on a number of sites as part of the SERC Pedagogic Service Project

Summary

Maxfield Soil Series Monolith
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A 4 minute video showing how to construct a soil monolith. A Quicktime ( 21.6MB May15 07) version is also available.

This extended exercise engages soils students in both field and laboratory work through the collection and preservation of a soil monolith, a vertical section of soil that has been extracted from an exposed soil profile in its natural position, treated to preserve the texture and structure of the soil as it appears naturally on the landscape, and mounted on a board for display.

Soil monoliths are excellent for educational purposes because although visual interpretation is an integral component of understanding soil profiles, it is not always possible or convenient to examine soil in situ. Soil monoliths make it possible for students to experience how soils vary both spatially and temporally across the landscape. Professional soil scientists, educators, and museum curators use monoliths to observe and analyze properties of a diversity of soils in one place.

Finished monoliths can be displayed at your university or donated to a museum so that others who are not able to examine that soil type in situ have the opportunity to observe a section of it.

Learning Goals

Soil Monoliths Ivory Coast
Soil Monoliths from Ivory Coast
Photo from ISRIC World Soil Museum

Context for Use

This exercise is best for students with some understanding of soil features such as horizons, texture, structure, and color and some experience describing soils. For this reason, it works well around the middle of an introductory soils course.

It is an extended exercise that consists of four field/lab days. Two days are spent in the field describing the soil and extracting the monolith. Two days are spent in the lab preparing the monolith, applying the fixative, and making the descriptive placards.

Depending on how you tailor this to your class, it will take about four weeks to complete all of the steps in this exercise. Allow time for the extracted monolith to dry between steps where indicated.

Teaching Materials

Teaching Notes and Tips

Step one, field: Observe and describe a soil profile
soil_char

This step will give students more experience describing soils in the field.

Find or make an exposure that is representative of a soil type or contains characteristics to which you would like to draw your students' attention. You can choose easy access exposures such as road cuts or have the students dig their own pit. Exposures should extend through the O, A, E, and B horizons and down into the C horizon or weathered rock. This requirement usually yields 1-1.5 meter-deep pits.

Have the students relate the five soil forming factors to the actual soil development. Students should take careful notes and describe in detail soil characteristics such as texture, color, structure, and horizonation. Information collected on this day will be used to create the descriptive placards that will accompany the finished soil monolith.

By the end of this field session, students should be able to produce the following:

  • Drawing of the soil profile using shades of gray or color
  • Accurate and detailed soil profile description containing as much information as possible
  • Summary report of the 5SFFs acting upon this soil and an interpretation of how, and to what degree, each SFF has influenced the development of this soil
  • Soil order determination

Refer to Soils are the Pits for an example of digging soil pits and describing soils.


Step two, field: Prepare profile face and extract monolith
extract monolith

This step gives students professional hands on experience as they extract a soil monolith.

Go back to the soil exposure where the students did the soil description for the previous step. If you have a large class, break them up into groups and make multiple soil monoliths so that each student can be involved in the process.

Have the students choose a section of the exposure and smooth out a vertical face in preparation for extraction. Keep in mind that this is the face that will eventually be displayed on the monolith.

Insert the metal frame from the extraction board into the profile face, cut back the sides, attach the extraction board, cut back the soil behind the frame, and as the soil is loosened, lower the extraction board and set it on flat ground.

Attach the mounting board to the extracted soil, remove the extraction board, and shave the soil down to your desired final thickness. Wrap the monolith in a sheet of plastic for transport back to your lab.

After the extraction, leave the exposure in a state as close as possible to the one in which you found it, bringing back all of your tools and filling in the pit if you dug one.

Transport the extracted soil monoliths from the field to the lab. If the soil is very moist, uncover it so it can dry until you begin the next step. If your soil is fairly dry, you can leave it covered in plastic until you can begin the next step.

For an example of these steps, see SERC's four-minute video How to Make a Soil Monolith.


Step three, lab: Prepare monolith face
soil structure lab

In this step, students restore the natural appearance of the soil before applying a permanent fixative.

When the soil was cut, the natural soil structure was obliterated. Pick out the soil face to reveal the natural structure as it is found in the field. If the soil is too dry, gently remoisten it with a water sprayer before picking out its natural structure.

When the natural soil structure is revealed, brush away any loose particles and clean the mounting boards by scraping or sanding off any dried glue.

If you have pebbles, parent material, or other loose features you want to include in the monolith, you can place them in their natural position on the profile either now or just before applying the fixative in step four.

The soil should be completely dry for the next step, so leave it out to air-dry if necessary.

For an example of these steps, see SERC's four-minute video How to Make a Soil Monolith.


Step four, lab: Apply fixative

Student makes water/glue mixture for soil monolith This step can be completed on the same day as either step three or five, depending on soil moisture level and amount of time available.

When the soil monolith is dry, saturate it with a water-glue mixture to solidify the soil and fix it permanently to the mounting board.

The ratio of water to glue used depends on the soil texture. In general, sandy/loamy soils take 5 parts water and 1 part glue, whereas clayey soils take 10 parts water and 1 part glue.

Pour glue fixative on soil monolith. Protect the mounting board with tape and paper and apply as many applications of the water/glue mixture as needed (2-3) to ensure complete saturation of the soil monolith. Make sure any loose pieces such as pebbles or parent material are in the correct places and that features such as burrows are visible. Do not let the fixative pond on the surface. When the soil is saturated, wipe excess glue from the mounting board and remove the tape.

Let the profile dry completely, preferably in a ventilated area. This may take one to two weeks.

While the water/glue mixture in the soil dries, you can begin step five and create the descriptive plaques, paint the mounting board, and add hanging hardware to the mounting board.

For an example of these steps, see SERC's four-minute video How to Make a Soil Monolith.


Step five, lab: Create plaques, paint board, add hardware
maxfield plaque

It is time to complete the finishing touches and get the soil monolith ready for display.

Creating descriptive plaques, painting the mounting board, and adding hanging hardware are the final steps in this multi-week exercise. These final steps can be completed while the water/glue fixative dries in the soil. The information and descriptions produced in step one will be useful here.


Descriptive Plaques
  • Obtain a site location picture of where the soil occurs
  • Type soil location description: general description of where the soil series is typically found
  • Type soil profile description: detailed description of the representative soil profile for the soil series
  • Mount soil location description with site photo and soil profile description on separate mounting boards for display alongside the finished monolith

Mounting Board

  • Paint the mounting board with a flat black paint
  • Add hanging hardware: attach eyehooks and chain to the top of each mounting board for hanging

Once the soil and paint are dry, your soil monolith is ready for display!

For an example of these steps, see SERC's four-minute video How to Make a Soil Monolith.


Download a pdf of Step-by-Step Instructions (Acrobat (PDF) 854kB Oct15 07).

Assessment

Observe field and lab work. Assess quality and accuracy of location and profile descriptions. Compare detail and accuracy of soil description with previous descriptions.

References and Resources

Belohlavy, F., 1994, Making Soil Monoliths Using White Glue as a Fixative: Soil Survey Horizons

Purdue University Cooperative Extension Service: How to Make Miniature Soil Monoliths


Subject

Geoscience:Geology

Resource Type

Activities:Lab Activity, Field Activity, Audio/Visual:Animations/Video, Activities:Field Activity:Importation of field observations into the classroom, Field laboratories, Activities:Project

Special Interest

Field-Based Teaching and Learning

Grade Level

College Lower (13-14):Introductory Level

Ready for Use

Ready to Use

Earth System Topics

Solid Earth

Topics

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