Soil Fundamentals Flashcards
What is a Pedosphere?
is the skin of the Earth and interfaces with the
atmosphere, biosphere, lithosphere, and hydrosphere
the outermost layer of the Earth that is composed of
soil and subject to soil formation processes.
It exists at the interface of
the lithosphere, atmosphere, hydrosphere and biosphere.
What factors affect the profile of a pedosphere?
the dynamic interaction between the
atmosphere, biosphere, lithosphere, and hydrosphere
lithosphere (minerals), biosphere (life), atmosphere
(air), and hydrosphere (water)
What does the lithosphere refer to?
minerals
What does the biosphere refer to?
life
What does the atmosphere refer to?
air
What does the hydrosphere refer to?
water
Why is the Pedosphere: a unique
medium
An arrangement of solids and pores in soil.
The pores are filled with air and/or water,
while the solids are composed of minerals, living and non living organic matter.
What is the relationship between the Pedosphere and Life
- The soil biota consists of microorganisms, soil fauna, and plants
- They form a food web in the soil
- Control decomposition of plant and animal
residue
**What is a Pedon?
A soil pedon is a 3D body in a landscape that can be divided into 4 main components:
1. air
2. organics
3. minerals
4, water
***Define Pedon
is the smallest volume that can be called a soil (1-10m2)
Define Polypedon
consists of more than 1 pedon
***Define Solum
The upper layer in soil, modified parent material, contain most plant roots
the upper horizon in a soil in which the parent material has been modified and in which most plants roots are contained
Define Aggregate
a group of soil particles cohering in such a way that they mechanically behave as a unit
Define Soilscape
a pedological portion of the landscape
Define Soil Ped
a unit of soil structure such as prism, block, or granule, which is
formed by natural processes
***Define Soil Horizon
a layer of soil or material approximately parallel to the land
surface (cm in thickness)
***Define Soil Profile
Vertical section of soil extending to the parent material
a vertical section of soil through all its horizons and extending into
the parent material (1-2 m)
How many interactions of spheres creates a pedon?
4 (ABHL)
A – Atmosphere
B – Biosphere
H – Hydrosphere
L – Lithosphere
***How many interactions of spheres create a pedosphere?
2 (any combo)
A – Atmosphere
B – Biosphere
H – Hydrosphere
L – Lithosphere
Why is the pedosphere important (2)?
The pedosphere is an integral component of many cycles: water, carbon, nitrogen
The pedosphere is a complex life support system for the plant
What are the soil forming factors (5)?
- Parent Material
- Climate
- Biota
- Time
- Topography
The process of Decay
Over time Plant Material decreases, and through Humification (decay), Humus increases
What are the soil process (3)?
- Physical (leaching, heat transport)
- Chemical (weathering of minerals)
- Biological (decomposition, mineralization)
What are the major components of soil (4)?
- Minerals
- Organic matter
- Water
- Air
List the soil profile
O - organics (humus)
A - Topsoil (minerals with humus)
B - Subsoil (deposited minerals and metals)
C - Parent Rock (partially weathered rock)
R - Bedrock (un-weathered rock)
Profile of the O horizon
L - leaf litter
F - Fermenting leaf litter
H - Humus
Define Rocks
naturally occurring combinations or coherent
aggregates of minerals, fossils or other hard materials
Metamorphic -> Igneous
Melting
Metamorphic -> Sedimentary
weathering, transportation,
lithification
Igneous -> Metamorphic
heat, pressure, ions
Igneous -> Sedimentary
weathering, transportation
lithification
Sedimentary -> Metamorphic
heat, pressure, ions
Sedimentary -> Igneous
Melting
Igneous Rocks
They were once molten and
upon cooling, the magma
(molten rock) crystallized
into solid rock.
Igneous rocks may form deep
inside the Earth or at the
Earth’s surface when a
volcano erupts
How do Igneous Rocks Form?
Intrusive vs Extrusive
Also known as primary rocks (first to be formed)
Intrusive - Slow cooling (of magma)
- Deep beneath the earth’s surface
- large crystals
Extrusive - Rapid cooling (of lava)
- Earths surface
- small crystals (not easily seen with the naked eye)
- cooling can be so rapid that glass forms instead of crystal
Examples of Extrusive igneous rocks
Pumice (the rapid cooling causes voids)
obsidian
Rhyolite
Andesite
Basalt
Perlite
Tuff
Volcanic Breccia
Examples of intrusive igneous rocks
Granite
Diorite
Gabbro
Peridotite
(think of granite and diorite counter tops, they have crystals)
SEDIMENTARY ROCKS
composed of particles derived from pre-existing rocks or by the crystallization of minerals that were held in solutions
What is a general characteristic of sedimentary rocks?
layering or stratification
Describe Fragmental/Clastic in sedimentary rocks
composed of pieces of rocks and minerals
These fragments show evidence of transport – rounding of the grains and size sorting.
describe CHEMICAL sedimentary
rocks are the result of either precipitation of solids from solutions
(like salt from water) or,
by organic process, like shells from marine organisms.
Examples of Fragmental Sedimentary Rocks
Conglomerate
sandstone
shale
How are sedimentary rocks formed
weathering, transportation
lithification
How are igneous rocks formed
melting
How are metamorphic rocks formed
heat, pressure, ions
Examples of chemical sedimentary Rocks
coal
chert
gypsum
diatomite
METAMORPHIC ROCKS
have changed (meta) their form (morphic).
Under the influence of heat, pressure and fluids, pre-existing rocks are modified in form and even in internal atomic structure to produce new rocks stable at the new conditions
done within the solid state, i.e. without melting
Describe foliated rocks
Metamorphic rocks that exhibit parallel alignments of minerals
the minerals all line up perpendicular to the exerted pressure.
Describe non-foliated rocks
Metamorphic rocks composed of minerals that are not elongated or flat, do not exhibit parallel alignments
Examples of foliated rocksMETAMORPHIC ROCKS
Slate
Gneiss
phyllite
schist
Examples of non-foliated rocks METAMORPHIC ROCKS
marble
quartzite
serpentinite
meta conglomerate
what are the characteristics of METAMORPHIC ROCKS?
non-foliated and foliated
what are the characteristics of SEDIMENTARY ROCKS?
Fragmental and chemical
what are the characteristics of IGNEOUS ROCKS?
Intrusive and Extrusive
What factors influence transportation (4)?
- Gravity
- Running water
- Glaciers
- wind
Gravity
includes landslides, forms loosely compacted host rock and is of minor importance
Alluvial
transported by moving water. Greater velocity = greater particle size
Glacial Deposits
action of glaciers-ice age
direct glacial deposits = moraines
Eskers
ridges or mounds of boulders, gravel and sand formed when such materials flowing in streams on, within, or beneath glaciers deposited as the streams bed load
Wind Deposits
also known as Aeolian deposits have wind as the transporting agent.
3 major groups of soil
- Non Cohesive
- Cohesive
- Organic
Define Non Cohesive soil
Soil particles do not tend to stick together
Excellent engineering properties; high bearing capacities
Examples: gravel, sand, silt
Define Cohesive soil
Very small particle size that tend to stick together
Water-particle interaction
Attractive forces between particles
These soils are sticky and plastic
Example: clay
Define organic soil
Typically spongy, crumbly, compressible
Low shear strengths
Undesirable for Civil Engineering applications
Example: use as a top soil for rehabilitation projects, ground cover for gravel pits
What is Atterburg limits
The addition of water greatly affects the plasticity of cohesive soils
Atterburg (1911,1912) defined four states of consistency for cohesive soils
1. Liquid
2. Plastic
3. Semisolid
4. Solid
What are the 4 stages of consistancy for cohesive soils defined by atterburg limits
- Liquid
- Plastic
- Semisolid
- Solid
liquid limit
The dividing line between liquid and plastic states
plastic limit
The dividing line between plastic and semisolid states
shrinkage limit
The dividing line between semisolid and solid states
Permeability
the movement of water within soil.
Water moves through soils with large voids(sand) which are more permeable than those with smaller voids (clay).
Capillarity
the rise of water (or other liquids) in a small-diameter tube inserted into the water, the rise being caused by both cohesion of the water’s molecules (surface tension) and adhesion of the water to the tube’s wall.
Frost Heave
When water in a soils mass drops below the freezing point, water in voids freeze, expands. This vertical expansion of soil caused by the freezing water within is known as frost heave
Shear strength
its ability to resist shear stresses. Shear stresses exist in a sloping hillside or result from filled land, weight of footings, and so on
If a given soil does not have sufficient shear strength to resist shear stresses, failures in the forms of landslides and footing failures will occur
frictional resistance to sliding, interlocking between adjacent solid particles in the soil, and cohesion between adjacent soil particles.
Mechanical Weathering
no change in chemical composition–just disintegration into smaller pieces disintegrates rocks into small particles by means of
- temperature changes - frost action - rainfall - running water - wind - ice - abrasion All of these actions involve breaking, grinding, and crushing
Chemical weathering
breakdown as a result of chemical reactions. Causes chemical decomposition of rock which can drastically change its physical and chemical characteristics.
This type of weathering results from; - reactions of rock minerals with oxygen, water, acids, salts This results in such processes as; - oxidation, solution, carbonation, leaching, hydrolysis
Chemical weathering process cause actions that can;
1 increase volume of materials resulting in subsequent material breakdown
2 dissolve parts of rock matter
3 react with cementing material
weathering vs erosion
Weathering is the process of breaking down rocks and minerals, while erosion is the process of moving the weathered material
*** The pedosphere is
- outermost layer of earth
- composed of soil and subject to soil formation processes
- Forms when there is an interaction between minerals, living organisms, air, and water
***Megma Vs Lava
megma is molten material beneath the surface in a volcano
Lava is molten material that has left the inside of the volcano at earth surface
***What is the key characteristic of intrusive igneous rock?
development of large crystals
*** How is pahoehoe formed
extrusive
igneous
surface cools/movement
the surface in contact with the air begins to crystallize, while the
fluid lava below continues to flow.
This drags the upper, still plastic, surface into a series of smooth wrinkles.
*** Fragmental or clastic sedimentary rocks show evidence of :
Transport
Rounding of grains
size sorting
*** Fosils would be most common in what type of rock
Sedimentary
*** Metamorphic rocks are formed without melting T/F
T
*** Changes that can occur in metamorphic rock include
increase in grain size
formation of new minerals
mineral alignment
** What are types of weathering
mechanical
chemical
***What are agents of transport for weathered rock
1, Gravity
2, moving water
3, glaciers
4. wind
*** deposition can occur through
1, gravity
2, alluviation
3, glacial movement
4. aeolian processes
*** non-cohesive soil has
excellent engineering properties
*** cohesive soil has
poor engineering properties
*** organic soil is
used for rehabilitation projects, not civil engineering uses
*** Attenburg defined these states of consistency for cohesive soils
- liquid
- plastic
- semisolid
- solid
***Attenburg defines the plasticity index (PI) as
The difference between liquid limit and plastic limit
***The AASHTO soil classification system includes
grain size
liquid limit
plasticity index
*** The void ratio, porosity and saturation of soils has implications to the potential ____ of contaminants in soil and groundwater
movement
*** Soils that can be easily saturated of soils that can easily absorb water is associated with
- porosity
- compressibility
- frost heave
