Soil Textures Exercise

Sizes of mineral particles are most commonly described in terms of the Wentworth scale (named after a prominent geologist who did pioneering research on sediments)

Wentworth Scale of Size Grades

            Grade Name                            Millimeters                                            Inches

            Boulders                                   over 256                                              over 10

            Cobbles                                   64 - 256                                               2.5 - 10

            Pebbles                                    2 - 64                                                   0.08 - 2.5

            Sand                                        0.0625 - 2                                            0.025 - 0.08

            Silt                                           0.004 - 0.0625                                     0.0016 - 0.025

            Clay                                         0.00024 - 0.004                                    0.000094 - 0.0016

Pie diagrams of points A, B, and C shown on ternary diagram.

 

 Numbers are percent sand, silt, and clay.

                                                                        Hatch = Clay, Vertical = Sand, Horizontal = Silt

1)         Refer to the ternary soil-texture diagram on the previous page.  Names of texture classes and boundaries are shown.  Estimate the limits (in percentage) of sand, silt, and clay that define the boundaries for each of the twelve classes.  Enter the percentages in the blanks below.

Class Name                                          % Sand                        % Silt                           % Clay

Sand                                                    _______                      _______                      _______

Loamy Sand                                         _______                      _______                      _______

Sandy Loam                                         _______                      _______                      _______

Loam                                                   _______                      _______                      _______

Silt                                                       _______                      _______                      _______

Clay                                                     _______                      _______                      _______

Sandy Clay Loam                                 _______                      _______                      _______

Clay Loam                                           _______                      _______                      _______

Sandy Clay                                           _______                      _______                      _______

Silt Loam                                              _______                      _______                      _______

Silty Clay Loam                                    _______                      _______                      _______

Silty Clay                                              _______                      _______                      _______

In the table below are percentages of sand, silt and clay for five different soil samples:

            Sample #                      % Sand                        %Silt                            %Clay

            1                                  15                                51                                34

            2                                  74                                13                                13

            3                                  10                                85                                5

            4                                  17                                31                                52

            5                                  47                                32                                21

2)         Locate each sample on the ternary diagram.  Make a dot and label it with the sample number.  In the spaces below, write the name of the soil texture class.

            Sample 1                      ________________________________

            Sample 2                      ________________________________

            Sample 3                      ________________________________

            Sample 4                      ________________________________

            Sample 5                      ________________________________

3)         Using the empty circles below, construct a pie diagram of each of the five samples.  Refer to the samples on the previous page.

                                                                                                             

Worth 2points. Due Thursday, 29 July.