Weathering and SoilNotes Sheet

Section One Weathering Effects of Weathering- surface processes break down into smaller

pieces called sediments

Mechanical Weathering- physical processes breaks rock into fragments with the same chemical makeup and characteristics as the original rock

Plant roots and burrowing animals cause mechanical weathering

Ice wedging- water enters cracks and freezes and expands, breaking rocks apart

Small pieces of rock have more surface area than the original rock and weather faster

Section One Weathering Chemical Weathering- chemical reactions dissolve minerals in rocks

or change them into different minerals Carbonic acid, formed from carbon dioxide gas and water, and

plants acid can react with minerals to weather rock Oxidation- chemical process that occurs when iron is exposed to

water and the oxygen in the air

Effects of Climate- pattern of weather that occurs in a particular area over many years

Mechanical weathering is more rapid than chemical weathering in cold climates

Chemical weathering is more rapid than mechanical weathering in warm, wet climates

Rock type can affect rate of weathering

Section Two The Nature of Soil Formation of Soil- can take thousands of years Soil is a mixture of weathered rock, decayed organic matter,

mineral fragments, water, and soil

Formation is influenced by climate, slope, types of rock, types of vegetation, and length of time that rock has been weathering

Composition of Soil- the ingredients that make up soil Clay, silt, and sand are small particles of sediments

Decaying, dark-colored plant and animal material called humus

Small spaces between soil particles my be filled with air or water

Section Two The Nature of Soil Soil Profile- made up of different layers of soil Horizon A- top soil layer

• May be covered with organic litter that may turn into humus• Fertile layer with more humus and less rock and mineral particles than

other soil horizons Horizon B- middle soil layer

• Contains less hums and is lighter in color than Horizon A• Minerals travel from Horizon A to Horizon B in a process called

leaching Horizon C- bottom soil layer

• Has very little organic matter and is not strongly affected by leaching

• Contains rock- the parent material of the soil• Glaciers can deposit soil that did not form from the bedrock beneath

it

Section Two The Nature of Soil Soil Types- differ in different places Different regions have different climates that affect soil

development

Parent rock affects soil formation and types of vegetation that grows in a region

Time affects soil development because the longer the weathering has occurred, the less the soil looks like the parent rock

Soil on steep slopes develop poorly

Section Three Soil Erosion

Soil erosion or loss is important because plants do not grow as well when topsoil is lost

Causes and Effects of Erosion- many human activities disturb the natural balance between soil production and soil erosion

Agricultural Cultivation- increased farming removes the plant cover, leaving soils open to wind and water erosion

Forest Harvesting- removes forest which increases erosion and particularly damages tropical rain forest soil

Overgrazing results when animals graze until almost all ground cover disappears

Urban Construction clear land of vegetation and removes soil

Section Three Soil Erosion

Preventing Soil Erosion- soil must be protected Manage crops

• Farmers plant shelter belts of trees to break the force of the wind• Bare soil can be covered with decaying plants to hold soil in place• Farmers graze animals on vegetation instead of plowing it under• With no-till farming, plants stalks are left in the field to provide

cover for soil

Section Three Soil Erosion

Reduces erosion on slopes

• Contour farming reduces soil erosion by planting along the contours of slops

• Terracing creates steep-sided flat areas for crops on the sides of hills and mountains

Reduce erosion at construction sites

• Exposed ground is covered with mulch

• Water is sprayed onto bare soil to reduce wind erosion

• Topsoil is replaces and trees are planted

• Seeded areas are reinforced with netting or straw

• Steeper slopes are protected by retaining walls