2. Weathering  It is surface processes that break down rock  Breaks rocks into smaller and smaller pieces  Ex.) Sand, silt, clay  The formation of soil depends on the amount of weathering that occurs

3. Weathering: 2 types  1.) Mechanical: when rocks are broken apart by physical means  Chemical make-up stays the same  Different factors can be mechanical weathering  1.) Plants and animals:  plants grow, roots wedge rocks apart  Animals push rocks and soil to the surface  2.) Ice Wedging: ice forms in cracks and then expands  3.) Surface Area: increases the amount of chemical weathering

4. Continued…  2.) Chemical Weathering: chemicals dissolve the minerals in the rocks and alter them  Different factors affect chemical weathering  Chemical composition is changed  1.) Natural acids: H 2 O and CO 2 mix, make weak acid  Ex.) Dissolve calcite, destroys the rock marble  2.) Plant acids: acids made from decaying plants  3.) Oxygen: causes oxidation  Oxidation is the same as rusting  Ex.) magnetite rusting to limonite

5. 10-2: Rates of Weathering  Takes a long time  Different factors can increase weathering rates though  Differential Weathering: softer, less weather resistant rocks wear away and leave harder more resistant rocks behind  Natural selection of the rock cycle

6. Different Factors: 1.Size and Surface Area:  Larger the surface area the more weathering will occur  Think of your face in the cold winter wind 2.Weather & Climate:  Chemical weathering increases in warm, humid climates  Water and temperatures also increases mechanical weathering  Ex.) Frost Wedging, heat buckling 3.Elevation:  Greater the slope the greater the mechanical weathering  Higher the peaks are the more weathering occurs

7. Ch. 10-3: Soil:  Soil: weathered rock, decayed organic matter, mineral fragments, water, and air  Can take thousands of years to form  Can be 60m or a few cm thick  There are 5 factors that affect soil formation:  1.) Climate  2.) Slope of land  3.) Types of rock  4.) Types of vegetation  5.) Amount of time rock has been weathered

8. Soil Composition:  We know what makes up soil  Most organic matter comes from plants though, not dead animals  When the plant and animal remains do decay by fungus and bacteria it becomes humus  Serves as a great nutrient supply for plants  Good surface soil has a ~50/50 mix of humus and rocky soil

9. Soil Profile:  Different layers of soil are called horizons  All horizons together form a soil profile  Horizon A: top layer  Covered with litter (leafs, plant remain etc.)  Known as topsoil  Horizon B: middle layer  Lighter then topsoil  Nutrients are leached to this level  Horizon C: bottom layer  Lowest layer  Not much organic material (light in color)  Under C or in C is rock

10. 10-4: Soil Conservation  What is it? Method to maintain soil fertility  Soil provides:  Minerals  Housing  Water Storage  Soil Damage and Loss:  Soil Erosion: movement of soil  Water, wind, gravity  How?  1.) vegetation is removed  2.) slopes are steepened

11. Soil Conservation techniques  1.) Contour plowing  2.) Terracing  3.) No-till farming  4.) Cover crop