Make up Lab on Forensic Science Soil Lab on Soil Texture
Percent of Sand, Silt and Clay
Mrs. Ashley
Name ____________________________________________
Make Up Lab
Please read through the lab below so that you know what was done for the lab that you missed.
This is one lab that is difficult to make up, so I am making an exception to allow you to do this
as a makeup lab. After you have read through the lab, go to the last section where it says:
"Questions for Make-up Lab" and answer those questions. The second set of questions:
"Further Research" are the added questions for you to do in place of the lab. Please use the
PowerPoint on soil, the other information from previous soil labs, and internet resources to
complete the table on sand types.
Lab:
For this lab you will be determining the soil texture, which is the percentage of sand, silt and
clay in the sample. Please follow the directions below and then use the soil texture triangle
below to determine the type of soil present. This is another method to help to differentiate
soils. Once you have completed the lab portion, please answer the questions that follow.
Determine soil texture
Soil is composed of particles that are categorized into groups according to their size, as shown
in the table below. One method of classifying soils is to measure the relative amounts of sand,
silt, and clay in a soil sample, then use a soil triangle to determine the soil type. In this lab, the
textural classification of a soil sample will be determined by measuring the relative amounts of
sand, silt, and clay particles, then using a soil triangle to determine the soil type. The
comparative volumes of sand, silt, and clay will be determined based upon the fact that the
different sized particles will settle out of a mixture at different rates.
Relative sizes of soil particles:
Clay
Silt
Sand
Gravel
< 0.002 mm
0.002 – 0.06 mm
0.06 – 2.0 mm
> 2.0 mm
1. Place a 40 to 50 mL of soil sample in the graduated cylinder.
2. Add water until the total volume of soil and water is about 80-100 mL. (You should add as
closely as possible the same amount of water as soil.)
3. Cover the top of the graduated cylinder with a piece of plastic wrap and secure it with a
rubber band.
4. Invert the cylinder several times until the soil is thoroughly suspended in the water. You may
have to shake the cylinder to mix the water and soil thoroughly.
5. Place the cylinder on the table and let the soil material settle for at least 30 minutes. The
different soil materials will settle to the bottom at different rates depending upon their
particle sizes: sand size > silt size > clay size.
6. Estimate and record the volume of the sand, silt and clay layers using the marks on the
graduated cylinder. There should be at least three reasonably distinct layers in the
graduated cylinder representing sand (bottom), silt (middle) and clay (top). There may also
be a dark humus layer above the clay layer, or possibly floating on top of the water.
7. Be sure to record the volumes of the three layers and the total of volume of your sample, and
calculate the percent composition by volume for each layer.
8. You will determine percent volume by the following formula:
Volume of sand________
Total Volume of soil added
X 100 = % sand
Volume of silt
Total Volume of soil added
X 100 = % silt
Volume of clay________
Total Volume of soil added
X 100 = % clay
9. Go to the soil texture triangle below and see what type of soil your two samples are and make a
comparison
Procedure for Use of the Soil Triangle
The soil triangle is used to determine textural classes of soil from the percentages of sand, silt,
and clay in the soil.
To determine soil texture using the soil triangle, the lines from each side must be extended in
the correct direction. Proceed as follows:
� Clay–extend line horizontal from the percent clay (parallel with side labeled sand)
� Silt–extend line downward from percent silt at 60° (parallel with side labeled clay)
� Sand–extend line upward from percent sand at 120° (parallel with side labeled silt)
For example, if a soil is 40% sand, 30% silt, and 30% clay, the texture is clay loam.
FIgure 1
Please answer the following questions:
Percent sand, silt and clay for sample 1
______ Sand
______Slit
______ Clay
Soil texture type: __________
Percent sand, silt and clay for sample 2
______ Sand
______Slit
______ Clay
Soil texture type: __________
Questions for Make-up lab
1. The proportions of what three particles are used to determine soil texture? Which of these
particles has the smallest surface area? Which has the largest?
2. Using the soil texture triangle (Fig. 1), to determine the type of soils with the following
particle sizes:
a. 20% silt, 10% clay, 70% sand _________________
b. 10% silt, 50% sand, 40% clay __________________
c. 40% sand, 10% silt, 50% clay __________________
d. 30% clay, 30% sand, 40% silt _________________
3. Looking at the Soil Texture Triangle (Fig. 1), which soil type has the greatest water retention
ability?
4. Looking at the Soil Texture Triangle (Fig. 1), which soil type has the least water retention
ability?
5. What are some other tests you could perform to distinguish between different soils?
Further Research
6. What type of soil texture is best for growing most crops? What makes this soil the best in
terms of the characteristics of the soil texture?
7.
Sand is one type of soil composition. It is formed by the action of wind and water on
rocks, called weathering. As wind and water mover rocks around, the rocks collide with other
rocks. This causes the rocks to break into smaller and smaller pieces until it becomes small
enough to become sand. Fragments contain two or more minerals and crystals contain only
one mineral. Sand varies in size from 0.05 mm to 2 mm in diameter. Sand may be angular or
rounded. The rounding process is from millions of years of weathering, usually in water this
process of rounding is slower than the rounding by wind.
Sand is classified as mature or immature based on its age. Mature sand has few
fragmented edges and lacks clay (this has eroded from the sand over time). Usually mature
sand is found near beaches where it has experienced long periods of weathering. Immature
sand is found close to where it was formed and not near waves or wind, such as in a swamp or
lagoon. There are four main classifications of sand based on the origin of the sand: continental
sand, volcanic sand, oolite or precipitate sand, and biogenic or skeletal sand. Sand is also
sometimes classified by the color of the sand which reflects what minerals are present.
Please research the sand types based on origin and complete the table below:
Use the following websites to help in your research:
http://www.sandatlas.org/sand-types/
http://www.sandatlas.org/2010/02/volcanic-sand/
http://www.sandatlas.org/sand-types/
http://www.soest.hawaii.edu/GG/ASK/beach_sand.html
http://sandcollectors.org/what-is-sand/
http://books.google.com/books?id=KehxbSii7tAC&pg=PT368&lpg=PT368&dq=Precipitate+sand
+oolite+sand&source=bl&ots=8KMJ4KybMh&sig=ysy1dBaKNVHROehc9yRA0Z2_5M&hl=en&sa=X&ei=HGSwUs_aNtOwsQSksYC4Dw&ved=0CFIQ6
AEwBQ#v=onepage&q=Precipitate%20sand%20oolite%20sand&f=false
http://geology.utah.gov/utahgeo/rockmineral/collecting/oolitic.htm
Table of Sand Types
Type of Sand
Continental
Sand
Volcanic Sand
Biogenic Sand
(Skeletal
Sand)
Oolite Sand
(Precipitate
Sand)
Characteristics including
color, shape, and mineral
composition
Source of material
and where found
How formed