Hawai'i Space Grant College, Hawai'i Institute of Geophysics and Planetology, University of Hawai'i, 1996

Describing Soils 
Purpose 

To describe, sort, and define soils on Earth. 

Key Words

 

soil 

particle size 

compaction 
 
 

Materials

 

soil sample 

magnet 

mass balance 

sieves of
different screen sizes

Background

 Soils are an important natural resource on Earth. Soils support plants and store organic matter. What do soils look like? Is a handful of soil just plain dirt or are there different kinds and sizes of particles?

 Procedure

1.
Collect a sample of soil to investigate.

 

2.
Where was this sample collected?

 
 
3.
Define soil:

 
 
4.
What color is it?

 
 
5.
What does it smell like?

 
 
6.
What does it feel like?

 
 
7.
Do you see any living or dead plants or animals?

 
 
 

8.
Make a sketch of the plants or animals you see.

 

9.
Does the sample contain any iron? Use a magnet to check.
10.
How many grams of iron are in your soil sample?
11.
Does the sample contain particles of uniform size? Use the sieves to check.
12.
Stack the sieves with the largest screen-size on top. Pour your soil sample down the sieve stack. What is the mass of soil particles collected in each sieve?

 
sieve grams of particles
#5  
#4  
#3  
#2  
#1  

13.
When soil is compacted and squeezed, it may or may not stick together. The way in which soil particles stick together gives us additional information about the types of particles present.

 Make a "putty" by mixing a small amount of soil and water in your hand. Try to form a "ribbon" of soil by squeezing your fist tightly closed. If the soil sticks together well, then the soil is mostly clays. If it sticks together moderately well, then the soil is loam, a mixture of sand and clay. If no ribbon can be formed, then the soil contains mostly sand and aggregate (broken rock pieces).

 How would you describe your soil sample after this simple compaction test?
 

14.
List any rocks and minerals you recognize in the soil sample.

 


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