Data Analysis Lab

Based on Real Data*

Interpret the Data

How can you determine a soil's texture? Soils can be classified with the use of a soil textural triangle. Soil texture is determined by the percentages of the sand, silt, and clay that make up the soil. These also vary with depth, from one soil horizon to another. Below are data from three horizons of a soil in North Carolina.

Data and Observations





















Data obtained from: Soil Survey Staff. 2006. National Soil Survey Characterization Data. Soil Survey Laboratory. National Soil Survey Center. (November 9) USDA-NRCS-Lincoln, NE

Data obtained from: Soil Survey Staff. 2006. National Soil Survey Characterization Data. Soil Survey Laboratory. National Soil Survey Center. (November 9) USDA-NRCS-Lincoln, NE

Think Critically

1. Examine the soil texture triangle shown in Figure 7.22 to complete the data table. Record the percentages of particle sizes in the soil samples and the names of their textures.

2. Infer from the data table which soil sample has the greatest percentage of the smallest-sized particles.

3. Identify which soil horizon contains a silty clay texture.

4. Infer, if water passes quickly through sand particles, what horizon will have the most capacity to hold soil moisture.

5. Identify one characteristic of soil, other than water-holding capacity, that is determined by the soil's particle size.

Soil Particle Sizes

Soil Color

The minerals, organic matter, and moisture in each soil horizon determine its color. An examination of the color of a soil can reveal many of its properties. For example, the layers that compose the O-horizon and A-horizon are usually dark-colored because they are rich in humus. Red and yellow soils might be the result of oxidation of iron minerals. Yellow soils are usually poorly drained and are often associated with environmental problems. Grayish or bluish soils are common in poorly drained regions where soils are constantly wet and lack oxygen.

Scientists use the Munsell System of Color Notation, shown in Figure 7.23, to describe soil color. This system consists of three parts: hue (color), value (lightness or darkness), and chroma (intensity). Each color is shown on a chip from a soil book. Using the components of hue, value, and chroma, a soil's color can be precisely described.

Section 7.3 Assessment

Section Summary

I Soil consists of weathered rock and humus.

I Soil is either residual or transported.

I A typical soil profile has O-horizon, A-horizon, B-horizon, and C-horizon.

I Five factors influence soil formation: climate, topography, parent material, biological organisms, and time.

I Characteristics of soil include texture, fertility, and color.

Understand Main Ideas

1. iman<TTflH Describe how soil forms.

2. Summarize the features of each horizon of soil.

3. Classify a soil profile based on whether it is mature or immature.

4. Generalize the effect that topography has on soil formation. Think Critically

5. Infer Soil scientists discover that a soil in a valley has a C-horizon of sand that is 1 km deep. Is this a transported soil or a residual soil? Justify your answer.

6. Hypothesize what type of soil exists in your area, and describe how you would determine whether your hypothesis is correct.

Earth Science

7. Soil in a portion of a garden is found to be claylike and acidic. Design a plan for improving the fertility of this soil.

Self-Check Quiz

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  • lisa
    How to analysis geological data in the lab?
    8 years ago

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