Erosion
The transport of loosened, dissolved or worn away rock and soil by natural processes. Erosion transports rocky material after layers of rock and soil have been broken down into smaller pieces

Agents- there are 4 agents of erosion, and there are at least 4 solutions to slow down the agents. The agents of erosion are Wind, Water, gravity and Glacial.

Solutions are Silt blankets, Silt walls, Gabion Walls and Multicellular underlay.
Silt Walls and Fences are simply placed at the foots of hills and slopes too stop wash-off. Silt Blankets are placed over the banks of gentle-sloping creeks and shores. Gabion Walls are made of large rocks which are interlocked together by the use of a metal netting. These walls are used as retaining walls on hills, rivers and creeks. Multicellular underlay is laid underneath the layers of soil and sediment. The Multicellular configuration holds the layers of soil in place.

Soil Conservation-
Soil conservation is maintaining good soil health, by various practices. The aim of soil conservation methods is to prevent soil erosion, prevent soil's overuse and prevent soil contamination from chemicals. There are various measures that are used to maintain soil health, and prevent the above harms to soil. Here are the soil conservation methods which are practiced for soil management.

Farming methods-
    Planting Vegetation: This is one of the most effective and cost saving soil conservation methods. This measure is among soil conservation methods used by farmers. By planting trees, grass, plants, soil erosion can be greatly prevented. Plants help to stabilize the properties of soil and trees also act as a wind barrier and prevents soil from being blown away.
    Contour Ploughing: Contour farming or ploughing is used by farmers, wherein they plough across a slope and follow the elevation contour lines. This methods prevents water run off, and thus prevents soil erosion by allowing water to slowly penetrate the soil.
    Watering the Soil: We water plants and trees, but it is equally important to water soil to maintain its health. Soil erosion occurs if the soil is blown away by wind. By watering and settling the soil, one can prevent soil erosion from the blowing away of soil by wind. One of the effective soil conservation methods in India is the drip irrigation system which provides water to the soil without the water running off.
    Salinity Management: Excessive collection of salts in the soil has harmful effects on the metabolism of plants. Salinity can lead to death of the vegetation and thus cause soil erosion, which is why salinity management is important.
    Terracing: Terracing is among one of the best soil conservation methods, where cultivation is done on a terrace leveled section of land. In terracing, farming is done on a unique step like structure and the possibility of water running off is slowed down.
    

Gravity & Erosion
    One of the principal sources of erosion is gravity, which is also the force behind creep, slumping (a large block of soil and rock), rockfalls, mudslides &  landslides    Creep is not quick or catastrophic but more mass movement actually occurs

Landforms shaped by Erosion
    Mountains- peaks, valleys, landslides, mudslides..
    Plains & Plateaus- Plateaus erode into hills & valleys or mesas
                Plains are not usually affected but change due to erosion

Soil is a mixture of weathered rock, micro-organisms, and organic remains that cover bedrock.

Its composition depends on the rocks that weathered and the local climate.

Physical weathered rocks break into small particles.  Chemical weathered rocks change minerals and often increase clay content.  Plants and animals add waste products and dead organisms.  They also burrow through and circulate water and air.  This will change the soils texture.

The gradual formation of soil in place produces layers we call horizons.  The top layer is the best layer for growing crops.  It is rich and dark and covered with organic matter we can call humus   (Not the food!!).  Some important minerals find their way to being transported deeper, usually by water. The lowest layer of soil is usually covered with broken bedrock.   Obviously the most weathering occurs on the top layer or Horizon A because it is exposed to all kinds of physical and chemical agents.  This area will also contain the most organic material.

In New York State, we do not usually show the complete development of soil profiles because much of our top layers were created as a result of glaciers moving southward and pushing everything in their way to our area.  So many of our rocks and soils actually originated far north of us and were broken down and transported as a result of the end of the ice age.
  
Soil Profiles-

Top layer- Horizon A- Top Soil- color gray to black and filled with organic
                        Material

2nd layer- Horizon B- subsoil- Usually red or brown, (lots of clay that has
                        Been washed downward)  Often the color comes from oxidation
                        Of minerals on Horizon A

3rd layer- Horizon C- Slightly weathered  parent material (rock fragments)
                                    From the bedrock that sits below.

 

 

Mass Movement of Soil-

      When we talk of mass movement, we are talking about a lot of soil moving at one time.   Gravity causes soil and rock fragments to fall, slide or move slowly down a slope.    Creep is the word we use for slow, downslope movement of soil

 

            Talus is a pile of rock fragments found at the base of a slope.  Talus piles are often found at the bottom of a cliff.

 

            Landslides are sudden movements, when bedrock or loose rock moves down a slope.  An avalanche is a landslide made of snow, ice or rock or mixtures of all of the above.

 

            Mudflow is the rapid movement of water saturated clay and silt.  It is especially fast and dangerous.

 

Protecting the Soil-  We need soil to grow food.  Human technology has contributed to the loss of soil by moving rocks for building, we do not have natural weathering of these rocks.  By destroying plant cover, like deforestation, more water gets to the soil and carries it away.  Salt used to melt ice on roads adds unwanted minerals to the soil and makes it difficult to grow things as a result.  We need to have undisturbed soil with plant covering and natural growth and weathering of rock in order for our world to continue to develop.

Deep within the Earth’s crust minerals are protected and remain stable, but when exposed to atmospheric conditions on the surface and in the hydrosphere, minerals undergo chemical changes.  When this happens, the rock changes into a new substance.

             The rusting of iron is an example of oxidation.  In this case iron is exposed to water and air and changes to form rust (iron oxide).  When feldspar is uplifted to the surface if forms clay. 
  
            Chemical weathering usually requires water to bring about mineral changes.  Chemical weathering takes place most rapidly in warm and moist climates.
  
            Some minerals resist chemical weathering.  Quartz (found in sand) resists most chemicals.  However olivine quickly weathers to clay when exposed to the atmosphere.
  
            Limestone is a hard rock that usually withstands physical weathering, however it is mostly made up of calcite, that when exposed to water decomposes and creates organic acid, while the rest of the rock becomes soluble in water and is carried away.    Water containing acid will only speed up the process.

Due to processes the include wind, water, ice, chemicals and gravity rocks break down to smaller pieces.   If they remain the same in composition, they probably mechanically weathered.  If they changed in composition, they chemically weathered.


Mechanical weathering is the same thing as physical weathering.  This means that the rocks are actually broken apart.  In this case the rock is exactly the same as it’s bigger sized original, except that it is smaller.   Rocks can be physically weathered by Ice wedging or Frost Action.    In this case, ice wedging refers to water getting into cracks freezing and expanding.  Frost Action is the freezing and warming of water which causes expansion and contraction and eventually leads to breaking.   Plant roots can cause mechanical weathering, as can wind.  Wind actually can weather by moving sand to almost “sand blast” pieces of a rock off.  We see this on monuments and stone statues like the Sphinx.    Flowing water from a stream can also weather rock.  We call this abrasion.  The constant bump and rub against the rock eventually breaks it down to particles which are carried by the stream and lead to further collisions and breaking down of other rocks.   Finally, gravity leads to breakage as well.  As rocks travel down hill they also bump and break, on the way down.   Waves are another type of water abrasion.  This constant attack on the rocks eventually wears and breaks rocks down.  

Mineral composition is a contributing factor in physical weathering, as harder minerals are difficult to break and softer minerals weather easier.  Quartz and Feldspar resist weathering, but often do break.  Mica and Calcite break apart easier.   Another mineral, Kaolinite (clay) weathers easily as well.