SOILS
WHAT IS SOIL?
IT IS NOT JUST, “DIRT”
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Soil Defined:
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formed from the weathering of rocks and organic activity and is composed of loose
rock fragments and clay derived from weathered rock mixed with organic material.
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Soil is primarily made up of, broken down rock (minerals) and organic materials
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(just like igneous rock, soil is made from the nutrients that are present inside of living
organisms)
HOW SOIL FORMS
The life cycle of soil begins whenever bed rock in the Earths surface begins to erode
over time.
Bedrock: Very solid layer of rock beneath the soil.
As bedrock begins to
erode, the small
eroded particles in the
bed rock will get
deposited onto the
surface of the earth,
where they begin to
form soil.
AS THE BEDROCK BEGINS TO ERODE, THIS IS
WHAT WE SEE HAPPENING OVER TIME
1. SOLID ROCK EXPOSED AT EARTH..
2. BEGINS TO ERODE INTO TINIER, MINERAL PARTICLES,.
3. A LAYER OF SOIL FORMS AT THE SURFACE, THIS LAYER IS A MIXTURE
OF VERY TINY SEDIMENT PARTICLES AS WELL AS ORGANIC
ORGANISIMS THAT MAKE THE SOIL HEALTHY FOR PLANT GROWTH
WHAT SOIL IS MADE OF
HUMUS- Decayed organic matter in soil.. Humus forms as plant and animal remains
decay. Humus is very rich in sulfur, phosporus, and potassium. (necessary for plant
growth.
SOIL HORIZON- MATURE SOIL THAT IS BROKEN
UP INTO THREE SECTIONS A-B-C
A-HORIZON: USUALLY DARK IN
COLORDUE TO A LOT OF ORGANIC
MATERIAL BEING PRESENT IN THE
SOIL. WHERE PLANT GROWTH
OCCURS
B-HORIZON- KNOW AS “SUBSOIL”
MADE OF TIGHTLY COMPACTED
CLAY- CLAY IS LIGHT AND IS
DEPOSITED FIRST ON THE
SURFACE
C- HORIZON- DEEPEST LAYER,
COMPOSED OF BROKEN BED
ROCK
FACTORS AFFECTING PLANT GROWTH
POROSITY AND PERMEABILITY
POROSITY :is a measure of how much soil is open space. This space can be
between grains or within cracks or cavities of the soil
.
PERMEABILITY
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Permeability is a measure of the ability of a rock or sediment to transmit water or
other liquids. Water does not pass through impermeable materials. A substantial
amount of water is stored in permeable soil and rock underground.
A COMMON TOPOGRAPHIC FEATURE EFFECT BY
POROSITY AND PERMEABILITYIS……
KARST TOPOGRAPHY
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What is Karst topography?
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topography developed in areas underlain by carbonate rocks, including limestone
and dolomite. Karst topography includes features like caves and sinkholes and forms
when limestone is slowly dissolved away by slightly acidic groundwater.
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KARST TOPOGRAPHY
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Karst topography occurs whenever groundwater begins to dissolve away the
limestone bed rock below the Earths surface
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The groundwater is in a layer of moist soil that travels through that layer of soil and
begins to dissolve the limestone in the Earth.
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Would this mean that the soil and limestone in these areas are highly permeable or not
very permeable?
WHERE KARST TOPOGRAPHY EXISTS IN
VIRGINIA