NOVA Online GOL 105 Soil and Weathering Lab_Jun2023_revision
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Northern Virginia Community College *
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Course
105
Subject
Geology
Date
Dec 6, 2023
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docx
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8
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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
Contains large amounts of
organic material and is mostly
mineral matter.Top layer is
mostly leaves and other organic
matter. Bottom layer is humus.
A Horizon
Mostly organic matter with high
biological activity and 30
percent humus
E Horizon
Light in color with little organic
material. Fine soil components
washed out by eluviation.
Leaching occurs.
B Horizon
Materials from E horizon are
deposited. Zone of
accumulation. Ability to better
hold water.
C Horizon
Partially altered parent material
Bedrock
Unweathered parent material
Revised: December 2018
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Revised: December 2018
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Table 2: Factors Affecting Soil Formation
Factor Affecting Soil Formation
Description
Parent material
Material that is weathered and gradually
goes through physical and chemical
changes from the process of soil
formation. Soils take on the color,
mineral composition, texture, structure,
of their parent material. Parent
material affects soil formation in two
ways being the rate of weatherinng
and the rate of formation. Chemical
makeup of the
parent material will affect the soils
fertility
Climate
One of the most major
infulences on soil formation.
Temperature and percipitation make the
most impact. These two together
determine whether chemical or
mechanical weathering will
greatly influence the
rate and depth of weathering
Plants and animals
They play a very vital role in soil
formation as the types and amount of
organisms highly affect the physical and
chemical properties of soil. Plants and
animals provide the majority of the
organic matter in soils.
Time
An important factor in soil formation.
The nature of soil is influenced by the
length of time of processes. For example
if weathering has only been happening
for a short time the soil will be
characterized by the parent soil. If
weathering has been occuring for some
time the parent material becomes
Revised: December 2018
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Factor Affecting Soil Formation
Description
overshadowed by other soil forming
fators.
Topography
The shape of the land affects soil form in
a significant way because the steepness
or slopes affect soil and the amount of
erosion and water content in the soil. On
steep slopes soils are poorly developed
as the run off water increases the
amount of erosion. But soils found in
the bottomland can get 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
Page 6 of 8
C
B
E
A
O
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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.
Photo courtesy of USDA NRCS
Revised: December 2018
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C
E
O
A
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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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C
A
E
B
O