SOIL ORIGIN and DEVELOPMENT SOILS are a SLOWLY RENEWABLE resource It takes 100’s to 1000’s of...

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)


• SEDIMENTARY ROCK – deposits of MUD and SAND (through wind and water erosion) that are CEMENTED together by CHEMICALS or PRESSURE


• 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


– PHYSICAL WEATHERING

• EROSION or wearing down of rock

– Water

– Wind


• WEATHERING of ROCK

– CHEMICAL WEATHERING

• DISSOLUTION - Water DISSOLVES minerals into SOLUTION



• HYDROLYSIS – Water reacts with minerals in rock create NEW, SOFTER COMPOUNDS



• OXIDATION – O2 reacts with minerals in rock to form NEW COMPOUNDS


• 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


– 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


– 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


– PARENT MATERIAL

• CUMULOSE SOILS – soils that accumulate in one spot

– Usually formed under WATERLOGGED conditions

– Containing > 20% organic matter


– 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


– 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


– TOPOGRAPHY- lay of the land • SLOPE – steepness of site

• ASPECT – which direction the slope faces


• 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)


• SOILS change over time in response to 4 processes…

– ADDITIONS– LOSSES– TRANLOCATIONS– TRANSFORMATIONS


• Because of these processes… LAYERS are formed in soils called HORIZONS

SOIL ORIGIN and DEVELOPMENT SOILS are a SLOWLY RENEWABLE resource It takes 100’s to 1000’s of...

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