Module 06 Part 1 Weathering and Soil Lab
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Northern Virginia Community College *
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Course
105
Subject
Geology
Date
Dec 6, 2023
Type
docx
Pages
11
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GOL 105: Weathering and Soil Lab
Objective:
The objective of this exercise is to help familiarize you with the basic soil profile, the processes responsible for creating each of the horizons within the profile, and the general characteristics of weathering of geologic material
.
Introduction:
This exercise will utilize the information contained in Chapter 6 (Weathering and Soil) in your textbook. All work can either be completed directly on this document (save it to your hard drive with a file name that includes your last name, then complete the exercise, save your copy, and then submit it via Blackboard). Another option is to print it, draw/write on the paper, then scan or photograph it to
make digital files capable of being submitted via Blackboard. Note that you will have to draw on several photos, either with pen/pencil or digitally.
Directions:
1.
Read Chapter 6
(Weathering and Soil) in your textbook.
2.
Complete Table 1
.
Identify the soil horizons in a typical soil profile. Fill in the
name of the soil horizons in the left hand column of the figure, and give a brief
description of the content and processes in each of the horizons in the left hand column. (10 pts)
3.
Complete Table 2
. Identify the five (5) most important factors affecting the development of a soil at any given location. List each factor separately in the left side column of the table, and then briefly discuss a few specifics on how this may affect the development of a soil profile. Which horizons will be most affected by each factor? (10 pts)
4.
Complete Figures 3, 4, and 5
. Try your hand at identifying the various soil horizons in each of these two figures. Draw the boundaries on the photo
, and clearly label each horizon with the corresponding letter (O, A, E, B, etc
.). Labels may be placed in the white space next to the photo for clarity. (10 pts)
Revised: December 2018
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Figure 1: A Typical Soil Profile
Name of soil horizon
Description
___O____ Horizon
This layer contains large amounts of organic material and
consists of mostly mineral matter. The top layer contains mostly plate litter such as leaves and other organic matter. The bottom layer consists of humus
.
___A____ Horizon
This layer consists of mostly organic matter, biological activity
is high, and humus is present up to 30%
___E____ Horizon
This layer is light in color and contains little organic material. Fine soil components are washed out by eluviation, and leaching occurs in this layer, which is the depletion of soluble
materials from the upper soil. ____B___ Horizon
In this horizon, the materials removed by eluviation in the E horizon are deposited. It is also known as the zone of accumulation because the accumulation of fine clay particles occurs on this horizon. This allows the horizon's capability to hold water to be enhanced. Revised: December 2018
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Name: _________________
Name of soil horizon
Description
____C___ Horizon
This horizon is noticeable by the partially altered parent material throughout. Bedrock
This layer contains unweathered parent material.
Revised: December 2018
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Table 2: Factors Affecting Soil Formation
Factor Affecting Soil Formation
Description
Parent Material
Parent material is weathered andgradually goes through physical andchemical changes as the process of soil formation. Soils take on the color,mineral composition, texture, structure,etc. of their parent material. Parentmaterial affects soil formation in twoways. One being the rate of weatherinngand the rate of formation. Secondlybeing the chemical makeup of theparent material will affect the soilsfertility
Climate
Climate is seen as one of the most majorinfulences on soil formation.Temperature and percipitation make the strongest impact.
These two togetherdetermine whether chemical ormechanical weathering willpredominatley or greatly influence therate and depth of weathering.
Plants and Animals
Plants and Animals play a vital role insoil
formation as the types and amountof organisms highly affect the phsical and chemical properties of soil. Plantsand animals provide the majority of theorganic matter in soil.
Time
This a very important factor in soilformation. The nature of soil is veryinfluenced by the length of time processes have been operating. Forexample, if weathering has only beenoccuring for a short time the soil will bemore characterized by the parent soil.However, if weathering has beenoccuring for some time the parentmaterial becomes overshadowed byother soil-forming factors
Revised: December 2018
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Factor Affecting Soil Formation
Description
Topography
The shape of the land affects soilformation in a significant way. Becausethe steepeness or slopes affect soil and the amount of erosion and watercontent in the soil. On steep slopes, soilsare poorly developed as the runoffwater increases the amount of erosion.But, soils found in the bottomland canbecome waterlogged.
Revised: December 2018
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Figure 3: Soil profile A
Description:
This soil profile shows the soil layers above the parent bedrock from which it was derived.
Photographer: Bruce Molnia, U.S. Geological Survey
Revised: December 2018
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Figure 4: Soil Profile B
Description:
Soil profile of Clarion soil, one of Iowa's soil types. The soil survey identifies all soil types and gives guidance on use of the more than 400 soil types
in the state. Note that the numbers running down the left side are depth in inches
. These numbers / lines are NOT meant to highlight the different horizons or their boundaries.
Revised: December 2018
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Photo courtesy of USDA NRCS
Revised: December 2018
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Revised: December 2018
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Figure 5: Soil Profile C
Description:
Here is a soil study excavation pit with well-expressed soil horizons. A meter stick and a pair of clippers (for trimming roots) serve as senses
of scale.
Photo by Gregory Lawrence
Revised: December 2018
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Revised: December 2018
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