Soil is composed of minerals, water, air and organic matter. It has distinct horizontal layers called horizons, including the O horizon at the top with partially decomposed organic matter, the A horizon or topsoil containing humus and living creatures, the B horizon or subsoil rich in minerals and clay but also containing roots, and the C and D horizons of weathering parent material and bedrock.
2. Soil
? Soil is a combination of minerals, water, air and organic matter. On average
there is
? 45% mineral matter
? 25% water
? 25% air
? 5 % organic matter
3. ? Minerals come from rock that have been weathered
? Water and air from the atmosphere
? Organic matter from the biosphere
13. Questions
? Which type of weathering leads to the build up of humus. ?
? Write one characteristic of subsoil that would make it good for plant growth.
? Write characteristics of subsoil that makes it inappropriate for plant growth.
Editor's Notes
#5: Cracks appear water enter cracks and expand when it freezes forcing the rocks apart
#7: An example of chemical biological weathering is when certain mosses, lichens, algae, fungi and even the smallest bacteria, will form on a rock, and will produce chemicals which (depending on the rock type) will eat away at the rock, giving the plant nutrients but also weathering at the same time.