Soil+and+Its+Uses

The Wonderful World of Dirt

First, a quick review of plate tectonics:
 * The Earth is composed of huge plates made up of the crust and the outer part of the mantle
 * These plates are slowly moved by the heat of the Earth
 * Plates collide and pull apart, and occasionally they cause giant earthquakes.

Soil
 * Rocks are created my tectonic plate motion, moltan rock cools to form new rock.
 * The rock weathers and erodes over time, leaving mineral fragments which mis with organic water, air, living organisms, and water.
 * Good soil is composed like this:
 * [[image:http://www.physicalgeography.net/fundamentals/images/soil_breakdown.gif width="428" height="253"]]
 * This combination provides good drainage, aeration and organic matter.
 * **Humus:** The organic material resulting from the decay of plant and animal remains.
 * Slope also can be an indicator of soil quality.
 * Soil Horizons
 * Oi Horizon - lots of loose organic debris not decomposed
 * Oa - Paritally decomposed organic matter.
 * A Horizon - topsoil, Has maximum biological activity.
 * E horizon - Leaching removes soluble minerals. Removal of materials or suspended in water occurs.
 * B Horizon - (subsoil) WHere the dissolved and suspended materials accumulate. Lots of silicate, clay minerals or iron and organic matter.
 * The lower the land is, the bigger the A horizon is and the smaller the B horizon is.