Soils - Assignment(1) (3) (1) (1).docx (1)
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University of Arkansas, Fayetteville *
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Course
1113
Subject
Geography
Date
Dec 6, 2023
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7
Uploaded by ChefLemur3909
LAB 9: Soils and Mass Wasting
100 points
Due one week after lab start.
LEARNING OUTCOMES
At the end of this lab, you will be able to
1.
Use a soil map to identify the soil series in a specific region.
2.
Determine the best land use for a region based on soil type.
3.
Classify soils based on texture.
INTRODUCTION
Soil is a mixture of organic and inorganic materials, together with air and water. Soil is
different from regolith, which is unconsolidated weathered material (i.e. disaggregated
bedrock). Soils display presence/formation of horizons and include organic activity.
Soil formation is a continuous process. There are four processes involved in soil
formation:
additions, removals, transformations
, and
translocations
.
Additions
are an external source of material to the soil, for example Saharan dust, volcanic
eruptions, leaf fall, soluble salts such as those found in acid rain.
Removals
refer to the removal of dissolved materials, organic and clay complexes through
groundwater (essentially erosion).
Transformation
is the weathering of organic and inorganic material, e.g.
organic matter into humic material.
Translocation
is the movement of chemical constituents, fine and course particles, and organics
either up or down through the soil profile.
These processes lead to organization of unconsolidated material and the development of a soil
profile, which is a vertical sequence of genetically related horizons.
A
soil horizon
is a distinct layer exposed in a profile that differs in mineral chemical and
physical properties. The master soil horizons are O, A, B, and C. The
O horizon
is
dominated by organic activity and consists of
≥
50 % organic material. The
A horizon
is
dominated by leaching (eluviation) of soluble and insoluble materials to lower horizons.
It is generally lightly colored. The
B horizon
is the zone of accumulation for the leachate
from the A horizon. The
C horizon
is regolith, and is essentially the parent material for
the soil.
Other master horizons may develop, depending on climate and topography.
These are E, K, and R. An E horizon is highly leached and derives it name from
Eluviation. It is very light in color. The K horizon is a zone of excessive deposition,
usually of lime or calcium carbonate. The R horizon is unweathered bedrock and is the
parent material of residual soils.
There are five factors that are involved in soil formation
. These are
climate, topography,
organisms, parent material
and
time
. The soils of an area tend to form in equilibrium
with these five factors. The factors account for the variation in soil types on a global and
local scale. They interact with each other on various levels, which results in diverse soil
series. Soil development is a very slow process taking thousands or even millions of
years (basically how long the soil has been exposed for).
Climate
includes temperature and precipitation. Temperature drives the weathering
of primary minerals organic materials. Precipitation is important because it controls
moisture availability and is important for translocation processes.
Organisms
modify the soil in a multitude of ways. Bacteria are important for the
breakdown of dead plant and animal matter, thus providing valuable nutrients for
plant uptake. Plants can help mix the soil and provide a cycle of nutrients within the
system. Earthworms aerate and mix the soil. Larger animals affect the plant
composition and so the impact on the soil. Humans modify soil to a large extent by
building and farming.
Topography
is important in several ways. It affects the rate and direction of water
movement across slopes. Slope stability and overall landscape stability is also a
factor in soil formation.
Parent material
reflects the nature of the underlying material, giving a soil its
basic chemical and physical characteristics, structure, texture, and color.
The length of
Time
that a soil has been forming is extremely important, as soil
formation is a continual process. Older soils tend to be deeper with greater horizon
development.
Soil Types
There are a great number of
soil types
across the globe. Therefore, a taxonomic system
is essential when talking about soils regarding their use for agriculture, engineering
and ecological applications. There is no one standard system and there are several in
use globally. The American system uses the
USDA Soil Classification
. It is a utilitarian
and considers steepness, length, and shape of slopes, drainage patterns, vegetation on
soils, and bedrock. Soil profiles are studied and delineated. Soils generally occur in an
orderly pattern related to geology, landforms, relief, climate, and vegetation of an area.
The USDA Soil Class Scheme is also a Linnean system with six hierarchical categories:
CATEGORY
NUMBER PER CATEGORY
Order
12
Suborder
47
Great Group
230
Sub Group
1200
Family
6000
Series
15,000 (in the USA)
Soil Orders:
Alfisols
: Occurs in the world bread basket; temperate forest soils
Andisols:
Volcanic soils
Aridisols:
Arid soils
Entisols:
New soils
Gelisols:
Frozen soils with permafrost
Histosols:
Organic soils
Inceptisols:
Young. Weekly developed soils
Mollisols:
Grassland soils (most naturally fertile on Earth)
Oxisols:
Tropical soils, extremely rich (usually red)
Spodosols:
Northern Conifer Forest Soils
Ultisols:
Highly leached forest soils
Vertisols:
Heavy clay soils, with high shrink/swell capacity.
There are some 15,000 soils series (or types) in the USA. To a great degree these soil
profiles determine the natural flora and fauna found in a particular area. They also
determine what kind of agriculture of forestry might be practical (if any) and the kinds of
structures that the soil will support. The Federal Court has accurately mapped the
detailed soil cover for most of the country, and knowing how to read these maps and
access the volumes of information they contain is important to many disciplines
(including agriculture, forestry, ecology, archaeology, engineering and real estate).
In this lab we are going to learn how to use the USDA Soil Survey of Yell County,
Arkansas. The County Soils Surveys are a very useful resource for land use planning.
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There are several map sheet subdivisions of the county, which are aerial photos
interpreted with the soil series. The Public Land Survey System (PLSS or Town and
Range) is the grid coordinate system used.
LAB 9: SOILS
Part I: Soil Mapping
Instructions: Use the soil map of Yell County, AR to answer the following questions.
1. What is the soil series at: SW ¼ of the NE ¼, Sec. 8, T6N, R20W? (5 pts)
Roellen
2. What is the soils series at SW ¼ of SW ¼, Sec. 8 T6N, R20W? (5 pts)
Roellen
3. Compare the agricultural value of these 2 soils. (5 pts)
They’re both in the same section and contain the same values and textures
4. What is the soil series at SW ¼, NW ¼, Sec. 10, T5N, R23W? (5 pts)
Carnasaw-Pirum-Clebit
5. What is the prime land use for this type of soil? (5 pts)
pasture and cultivated crops
6. What is the optimum soil type for the development of a wetland habitat reserve in Yell County?
Where are you likely to find those soils? (Hint use the Legend). (5 pts)
Carnasaw-Pirum-Clebit, located mostly in the South
Part II: Soil Classification
Instructions: Work in groups to identify the three different soil types provided and answer the
following questions.
7. In groups, use this
USDA soil texture flow chart
to examine and classify each of your soil samples. One
of these samples is
peat
and does not appear on the flow chart! (10 pts)
Sample 1:
peat
Sample 2:
Sandy Loam
Sample 3:
Silty Clay Loam
8. Based on your classification, which soil would be better for agricultural use? Why? (10 pts)
Sandy Loam would be the best choice for agricultural use because it can hold water together.
9. Compare the permeability of these three soils. Which soil sample would be most likely to contribute to
flooding due to low permeability? (10 pts)
Peat
10. What soil order do most of the soils found in Arkansas belong to? What is the primary texture of
these soils? (10 pt)
Mollisols, dark colored & thick, grassland soils
Instructions: Use the Geologic Map of Arkansas to answer the following questions.
11. Open the Geologic Map of Arkansas PDF (can be found in this lab folder in Blackboard) and locate
Fayetteville. Using the color-coded key, list three different geologic formations that can be found in
Fayetteville. (10)
a)
Bloyd Shale, Prairie Grove Member of the Hale Formation
b)
Pitkin Limestone
c)
Boone Formation
12. Follow
this link
and find the three geologic formations you identified in question 11. What types of
rocks and/or minerals are prevalent in each formation? (10 pts)
a)
("honeycomb weathering"), light-gray to dark-brown, limy sandstone or variously sandy limestone
with lenses of relatively pure, crinoidal, highly fossiliferous limestone and oolitic limestone.
b)
gray & blue gray fossiliferous limestone
c)
gray, fine- to coarse-grained fossiliferous limestone interbedded with chert. Some sections may
be predominantly limestone or chert. The cherts are dark in color in the lower part of the
sequence and light in the upper part.
13. Look at the Geologic Map of Arkansas PDF, and the Ecoregions of Arkansas map below, noting any
similarities in patterns between the two maps (i.e. does a particular land cover type seem to overlap
with a particular geologic substrate?). (10 pts)
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●
The split of the types of land cover is reflective of the geologic substrate like Pine Forest and
Clardy overlap.
Arkansas Statewide Forest Resource Assessment 2018