SOIL Definitions Bedrock Solid unweathered base rock Regolith

SOIL

Definitions § Bedrock – Solid, un-weathered base rock § Regolith – Broken up rock particles

4 Components of Soil

Rock Material in Soil § Sand - Largest component (2 mm – 0. 06 mm) § Composition (parent material) = Quartz § Source = Mechanical weathering

Rock Material in Soil § Silt (0. 06 mm-0. 002 mm) § Composition - feldspar & quartz § Source - mechanical weathering

Rock Material in Soil § Clay - less than 0. 002 mm § Composition (parent material)– feldspar § Source – chemical weathering

Which soil is best? § Sandy Soil? l Pro vs. Con § Silty Soil? l Pro vs. Con § Clay Soil? l Pro vs. Con

Soil Sizes § Sand (largest) § Silt § Clay (smallest) § Loam (mix of all 3)

Soil Texture

TAKE OUT YOUR OBJ. NOTES Pick up your papers from back

Soil Profile § A cross section of soil showing the different layers (horizons) § Horizons l l l A (O) B (E) C DRAW THIS

SOIL PROFILE § A- HORIZON: Organic material § B-HORIZON: area where nutrients from A are “leaching” down. § C-HORIZON: mostly parent bedrock, unweathered material.

SOIL HORIZONS § A- horizon top soil rich in organics humus- decaying leaves § B- horizon plant roots anchor here § C- horizon bedrock

Tropical - Rainforest § Thin A + B § lots of chemical weathering, but nutrients are used quickly § why?

Desert Climate § § thin A + B little nutrients little weathering why?

Polar soil § thin A + B § few nutrients § little chemical weathering § why? ? ?

Temperate Climate § Thick A + B § lots of nutrients § good farmland § lots of chem. + phys. weathering § why?

Importance of soil § Food chain § Filters groundwater § 1 cm = 1, 000 years formation § Providing resources for world to survive.