Soil Textural Triangle Worksheet printable pdf download

Soil Textural Triangle

Name: _________________________________________________ Period : _______ Date: _________

Essential Question: How do I classify the types of soil using the soil triangle?

A soil texture triangle is used to classify the texture class of a soil. The sides of the soil

texture triangle are scaled for the percentages of sand, silt, and clay.

Soil Texture is one of the first things

determined when a soil is examined. It is

related to weathering and rocks as parent

materials. The differences in horizons may be due to the

differences in texture of their respective parent materials

or rocks where soil formed.

First, look at the orientation of the percentages on the sides of the triangle. The numbers are arranged

symmetrically around the perimeter. On the left the numbers correspond to the percentage of clay, and

on the right the numbers correspond to the percentage of silt. At the bottom of the triangle chart are the

percentages of sand.

To classify a soil sample, you find the intersection of the

three lines that correspond the three proportions. On the

chart, all of the percents will add up to 100%.

Example: Classify a soil sample that is 30% clay, 15%

silt, and 55% sand. First locate 30% on the clay axis, and

draw a line horizontally from left to right. Next, locate 15%

on the silt axis, and draw a line going down diagonally to the

left. Finally, locate 55% on the sand axis, and draw a line

going up diagonally to the left. The intersection is in a region

called Sandy Clay Loam. See figure on the right.

In some environments clay aggregates form that are so strongly cemented together that they feel like fine

sand or silt. In humid climates iron oxide is the cement. Humid air can hasten the process of rusting, which an

example of chemical weathering.

Chemical weathering occurs when the minerals within the rocks are

chemically altered. Oxidation represents a form of chemical weathering where oxygen combines with

elements in the rock to form oxides. Iron-rich rocks provide a simple example of this: Oxidation results in

In desert climates silica is the cement and in arid

a rusting effect similar to the rust found on exposed iron.

regions lime can be the cement. It takes prolonged rubbing to show that they are clays and not silt

loams.Some soils derived from granite contain grains that resemble mica but are softer. Rubbing breaks down

these grains and reveals that they are clay. These grains resist dispersion and field and laboratory

determinations may disagree.

Soil Textural Triangle Worksheet