Transcript SOIL ORIGIN and DEVELOPMENT

SOIL ORIGIN and DEVELOPMENT
• SOILS are a SLOWLY RENEWABLE resource
It takes 100’s to 1000’s of YEARS for SOILS to
DEVELOP…
…but they do GROW, CHANGE, and DEVELOP
over TIME
ROCKS, MINERALS and NUTRIENTS
• ROCK (solid bedrock of earth’s crust) is broken down to
PARENT MATERIAL (smaller rocks) and through the
process of WEATHERING is further broken down to SOIL
– ROCK – Solid bedrock which is a mixture of MINERALS of
DIFFERENT KINDS and PROPORTIONS
– MINERALS – PURE INORGANIC ELEMENTS or COMPOUNDS of
a DEFINITE CHEMICAL COMPOSITION usually CRYSTALLINE
in form
– NUTRIENTS – Dissolved IONS in water called the SOIL SOLUTION
ROCKS - 3 MAJOR CLASSIFICATIONS
• IGNEOUS ROCK – created by the COOLING and
SOLIDIFICATION of MOLTEN ROCK
– LAVA (extrusive) & MAGMA (intrusive)
ROCKS - 3 MAJOR CLASSIFICATIONS
• SEDIMENTARY ROCK – deposits of MUD and SAND
(through wind and water erosion) that are CEMENTED
together by CHEMICALS or PRESSURE
ROCKS - 3 MAJOR CLASSIFICATIONS
• METAMORPHIC ROCK - formed when either IGNEOUS or
SEDIMENTARY ROCK is subjected to GREAT HEAT &
PRESSURE
SOIL FORMATION
• SOIL is formed from the
WEATHERING of ROCK
– PHYSICAL WEATHERING
• FRACTURING due to
expansion and contraction
– Frost Wedging - freezing
and thawing of water
– Heating and cooling
SOIL FORMATION
– PHYSICAL WEATHERING
• EROSION or wearing down of rock
– Water
– Wind
SOIL FORMATION
• WEATHERING of ROCK
– CHEMICAL WEATHERING
• DISSOLUTION - Water
DISSOLVES minerals into
SOLUTION
SOIL FORMATION
– CHEMICAL WEATHERING
• HYDROLYSIS – Water reacts
with minerals in rock create NEW,
SOFTER COMPOUNDS
SOIL FORMATION
– CHEMICAL WEATHERING
• OXIDATION – O2 reacts with
minerals in rock to form NEW
COMPOUNDS
SOIL FORMATION
• WEATHERING of ROCK
– PLANTS ….can also PHYSICALLY and
CHEMICALLY WEATHER ROCK
• ROOT WEDGING – Plant roots
PHSICALLY force open cracks by
ROOT GROWTH
• LICHENS – exude acid which
CHEMICALLY WEATHERS rock
FACTORS AFFECTING SOIL FORMATION
• The TYPE of SOIL developed depends on the
amount of TIME a PARENT MATERIAL of a
specific TOPOGRAPHY is exposed to the effects of
CLIMATE and VEGETATION (or LIFE).
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PARENT MATERIAL
CLIMATE
LIFE
TOPOGRAPHY
TIME
FACTORS AFFECTING SOIL FORMATION
– PARENT MATERIAL – are broken up rocks that
have started that process of WEATHERING
• RESIDUAL SOILS - are soils formed in PLACE
– Less common
– Form SLOWLY from weathering
FACTORS AFFECTING SOIL FORMATION
– PARENT MATERIAL
• TRANSPORTED SOILS –
are soils that have been
TRANSPORTED and
DEPOSITED from the
original site to another
– More common
– Form FASTER
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GLACIAL ICE
WIND
WATER
GRAVITY
VOLCANIC ACTION
FACTORS AFFECTING SOIL FORMATION
– PARENT MATERIAL
• CUMULOSE SOILS –
soils that accumulate in
one spot
– Usually formed under
WATERLOGGED
conditions
– Containing > 20%
organic matter
FACTORS AFFECTING SOIL FORMATION
– CLIMATE
• Temperature
– Decreased Temp >>> decreases weathering >>> soil forms
slower
– Decreased Temp >>> decreases decomposition >>> increases
OM overall
• Rainfall
– Increased rainfall >>>increases leaching of nutrients
– Increased rainfall >>>increases plants >>> increases OM
FACTORS AFFECTING SOIL FORMATION
– LIFE
• PLANTS affect soils
– GRASSLANDS vs.
FORESTS
• SOIL BIOLOGY – all
sorts of ORGANISMS
that aid in mixing, OM
decomposition, holding
and releasing of WATER
and NUTRIENTS
FACTORS AFFECTING SOIL FORMATION
– TOPOGRAPHY- lay of the land
• SLOPE – steepness of site
• ASPECT – which direction the slope faces
FACTORS AFFECTING SOIL FORMATION
• TIME
– The longer the TIME, the
MORE DEVELOPED the
SOIL PROFILE
• 0 year – when soil first
exposed to atmosphere
• YOUNGER SOILS show
fewer layers in the profile
• OLD SOILS show more
layers
SOIL PROFILE
• To STUDY SOILS we dig a pit called a
PEDON (3’ x 3’ x 5’ deep)
SOIL PROFILE
• SOILS change over time in response to 4
processes…
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ADDITIONS
LOSSES
TRANLOCATIONS
TRANSFORMATIONS
SOIL PROFILE
• Because of these processes… LAYERS are
formed in soils called HORIZONS