EARTH SCIENCE NOTES (original notes by Mrs. Schwab) Weathering & Soil EARTH SCIENCE NOTES (original notes by Mrs. Schwab)

WHAT IS WEATHERING? Weathering is a collection of ways that minerals and rocks are broken or worn down into bits and pieces. The bits and pieces of the original rock are called sediment.

CHEMICAL WEATHERING Rocks are chemically changed New products are formed

CHEMICAL WEATHERING (EXAMPLES) Oxidation – Rust – Iron Oxide Iron + Oxygen = Iron Oxide Carbonic Acid CO2 + Water = Carbonic Acid Dissolves rocks

SPEED OF REACTION The speed at which chemical weathering happens: increases when weather is: Warm Moist

MECHANICAL WEATHERING Physical Weathering Breakup of rocks to smaller pieces No new materials No chemical changes

TYPES OF MECHANICAL WEATHERING Day/Night Cycle Daytime – rocks heat up & expand Nighttime – rocks cool & contract Repeated – cracks form in rocks

TYPES OF MECHANICAL WEATHERING Frost Action (Ice Wedging) Water seeps into cracks in rock Water expands when frozen Ice cracks rock Water melts Water seeps further into crack in rock

TYPES OF MECHANICAL WEATHERING Animals Insects & burrowing animals dig holes into soil Holes allow water & air to reach rocks Rocks crack due to water action

TYPES OF MECHANICAL WEATHERING Plant/Tree Roots Roots move through soil – water & air move down to rock layer – water freezes Roots move into cracks in rocks Roots grow – crack gets bigger Roots split rocks

SPEED OF REACTION Weather changes Amount of water Warm - increase - plant growth/animal movements Cold – increase - water freezes Amount of water Little water – decrease – deserts/polar areas More water – increase – rainy / snow areas

SOIL Rock fragments Organic Material Dirt (slang) Decomposed plants/animals Plant roots Insects & worms Bacteria Dirt (slang)

SOIL PROFILE Cutaway view of soil layers Mature soil has 3 layers Layer = Horizon

SOIL HORIZONS Horizon A Top Soil Upper most layer of soil Few rocks – More organic material Humus - Organic material in soil – gives dark color Leaching – Minerals carried to lower level by water

SOIL HORIZONS Horizon B Subsoil Larger rock fragments – Little organic material Some leaching Lighter color than Horizon A

SOIL HORIZONS Horizon C 1st stage of soil Partly weathered rock – No organic material Rock chunks – almost no organic

SOIL HORIZONS Bedrock - solid unchanged rock Determines soil make-up Determines soil thickness (speed weathering)

WHERE THE BEST SOIL IS River Flood Plains Valley Areas River Deltas Great Plains

WHERE POOR SOIL IS Mountains Steep Slopes

TYPES OF SOIL Clay Soils Fine Grained Water does not move easily Feldspar minerals Aluminum Common in Bradford County

TYPES OF SOIL Sandy Soils Coarse grained Water moves easily Quartz minerals Rare in Bradford County

HEALTHY SOIL Soil one of most economically important resources on Earth Material supports plant life & so all life Soil is source of nutrients for all plants 16 Elements needed Air & water provide H,O, N, C Minerals from rocks P,K,Ca

HEALTHY SOIL Erosion Control Soil Conservation keeps soil in place Decrease nutrient loss Conserve water in soil

SOIL LOSS Erosion of soil is natural process Soil moves from one place to another Slow process

CAUSES OF SOIL LOSS Removal of plant cover (Plowing, Construction) Overgrazing Desertification Forest Harvest (cutting trees) Floods

PREVENTION OF SOIL LOSS Crop Rotation Each year plant different crop in field Each crop removes/replaces different minerals Recycle old nutrients Corn - oats - clover

PREVENTION OF SOIL LOSS Contour Plowing Plant across direction of water flow Plant across slope NOT up/down Reduces water erosion - runoff

PREVENTION OF SOIL LOSS Strip Cropping Alternating sections of crop Corn – grain Terracing Step cropping on a slope Grape Vines – Rice in China No-Till Farming Harvest but do not plow in fall