SOIL ORIGIN and DEVELOPMENT SOILS are a SLOWLY

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 ROCKS - • IGNEOUS ROCK – created by the COOLING and SOLIDIFICATION of MOLTEN ROCK – LAVA (extrusive) & MAGMA (intrusive)

ROCKS - 3 MAJOR CLASSIFICATIONS ROCKS - • SEDIMENTARY ROCK – deposits of MUD and SAND (through wind and water erosion) that are CEMENTED together by CHEMICALS or PRESSURE

ROCKS - 3 MAJOR CLASSIFICATIONS ROCKS - • 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 – O 2 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). – 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 • • • 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 5’ deep)

SOIL PROFILE • SOILS change over time in response to 4 processes… – ADDITIONS – LOSSES – TRANLOCATIONS – TRANSFORMATIONS

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