Most soils have horizontal layers known as soil horizons. These differ in their physical, chemical and organic composition. Several geological processes affect the formation of soil horizons. The weathering of rock and succession of plants to form the particles of sand, clay, silt and organic matter is discussed in the earthcache "Getting the Good Dirt." Once the soil has formed eluviation (the downward transport of fine particles (eg clay) by rainfall can occur. This may change the layer that this material is leached from and the layer that it is deposited into. They are absent in soils which have not had enough time to form horizons (eg sand, swamp, glacial moraine, ash, river gravel) and where there has been significant human disturbance (eg landscaping, excavation). A vertical column of soil showing these soil horizons is known as a soil profile. Soil scientists usually obtain these by using an auger or the good old fashioned spade. Road cuttings provide an excellent opportunity for viewing soil profiles without the sweat! A Typical Soil Profile: Thanks US Dept of Agriculture! Organic matter: Litter layer of plant residues in relatively undecomposed form. Surface soil: Layer of mineral soil with most organic matter accumulation and soil life. This layer eluviates (is depleted of) iron, clay, aluminum, organic compounds, and other soluble constituents. The layer E may be found below this when eluviation is pronounced. Subsoil: This layer accumulates iron, clay, aluminum and organic compounds. Parent rock: Layer of big unbroken rocks. Note: these are the common horizons, refer to sources for other horizons.
Logging Requirements
0. Email the following answers to us. Include the GC
1. Using the information above identify which soil horizons are present at GZ?
2. How thick are each of the horizons?
3. How long do you think it took the erosion to occur?
4. Post a pic at GZ (we would love to see you there!)