Do Now:

•Read the Short story from John Muir, then answer the following questions:

•1. Why is soil an important part of our environment? T and T

•2. What are ways soil can be weathered?

Aim: Why is soil an important resource?

I. Soil is more than just dirt.

Complex, ancient material teeming with living organismsCategorized by physical & chemical features

color & texture How does soil form?

A. Soil Origin

Weatheringprocess that breaks rock into smaller pieces

first step in soil formation

http://schoolworkhelper.net/wp-content/uploads/2011/01/soil20-chemical-weathering.gif

1. Physical weathering

Aka mechanicalDoesn’t change the chemistry of the rockForces= wind and water

2. Chemical weathering

Result of chemical interactions between water, minerals in the rock and other atmospheric gases.

3. Biological weathering

result of the activities of living organisms

Severe erosion following tropical forest removal, Madagascar. What role does vegetation play?

Evacuated ocean front homes from cliffside erosion & heavy rains due to "El Nino" in 1998. What type of erosion is this?

B. Soil Texture Categories by U.S. Dept. of Agriculture (USDA)

Clay- particles < 0.002mm in diameterEasily sticks together, really compactedLittle pores so it can hold little water

Soil Textures Continued:

Silt- particles 0.002 - 0.05 mm in d

Sand- particles 0.05 - 2.0 mm in dToo large to easily stick, looseLarge pores so it can hold more water

C. Soil Acidity & AlkalinitypH range= #0-14Tells you the [] of hydrogen ions

Soils pH is usually between 4-8 Neutral/slightly acidic

Acidity: How acidic the soil is.pH = 0-6

Alkalinity: How basic the soil ispH = 8-14

1. pH affect on soil

pH affects solubility of nutrientsDetermines the nutrients available for absorption by plant rootsIf too acidic/basic, certain soil nutrients will not be able to be used by regional plants

2. When soil becomes too acidic…

ions of heavy metals like mercury (Hg) or aluminum (Al) can leach onto the ground water which can travel to streams & rivers

harming plant & aquatic lifeEx: aluminum ions can damage the gills of a fish and cause them to suffocate