soil origin and development soils are a slowly renewable resource it takes 100’s to 1000’s of...
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SOIL ORIGIN and DEVELOPMENTSOIL 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 NUTRIENTSROCKS, 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 - ROCKS - 3 MAJOR CLASSIFICATIONS
• IGNEOUS ROCK – created by the COOLING and SOLIDIFICATION of MOLTEN ROCK– LAVA (extrusive) & MAGMA (intrusive)
ROCKS - 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 - ROCKS - 3 MAJOR CLASSIFICATIONS
• METAMORPHIC ROCK - formed when either IGNEOUS or SEDIMENTARY ROCK is subjected to GREAT HEAT & PRESSURE
SOIL FORMATIONSOIL 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 FORMATIONSOIL FORMATION
– PHYSICAL WEATHERING
• EROSION or wearing down of rock
– Water
– Wind
SOIL FORMATIONSOIL FORMATION
• WEATHERING of ROCK
– CHEMICAL WEATHERING
• DISSOLUTION - Water DISSOLVES minerals into SOLUTION
SOIL FORMATIONSOIL FORMATION
– CHEMICAL WEATHERING
• HYDROLYSIS – Water reacts with minerals in rock create NEW, SOFTER COMPOUNDS
SOIL FORMATIONSOIL FORMATION
– CHEMICAL WEATHERING
• OXIDATION – O2 reacts with minerals in rock to form NEW COMPOUNDS
SOIL FORMATIONSOIL 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 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).
– PARENT MATERIAL– CLIMATE– LIFE– TOPOGRAPHY– TIME
FACTORS AFFECTING SOIL FORMATION 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 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
• GLACIAL ICE• WIND• WATER• GRAVITY• VOLCANIC ACTION
FACTORS AFFECTING SOIL FORMATION 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 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 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 FACTORS AFFECTING SOIL FORMATION
– TOPOGRAPHY- lay of the land • SLOPE – steepness of site
• ASPECT – which direction the slope faces
FACTORS AFFECTING SOIL FORMATION 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 PROFILESOIL PROFILE
• To STUDY SOILS we dig a pit called a PEDON (3’ x 3’ x 5’ deep)
SOIL PROFILESOIL PROFILE
• SOILS change over time in response to 4 processes…
– ADDITIONS– LOSSES– TRANLOCATIONS– TRANSFORMATIONS
SOIL PROFILESOIL PROFILE
• Because of these processes… LAYERS are formed in soils called HORIZONS