Soil
Soil is a natural body consisting of layers (soil horizons) that are primarily composed of minerals which differ from their parent materials in their texture, structure, consistency, colour, chemical, biological and other characteristics. It is the unconsolidated or loose covering of fine rock particles that covers the surface of the earth. Soil is the end product of the influence of the climate (temperature, precipitation), relief (slope), organisms (flora and fauna), parent materials (original minerals), and time. In engineering, soil is referred to as regolith, or loose rock material: this is the 'drift deposit' lying on top of the 'solid geology'. However, in horticulture, the term 'soil' is defined as the humic layer of topsoil, or the depth of regolith containing organic material that influences and has been influenced by plant roots and may range in depth from centimetres to many metres. Expressions such as lunar soil or Martian soil are commonly used for extraterrestrial regolith, even though there is no known biological component.
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Famous quotes containing the word soil:
“The constant abrasion and decay of our lives makes the soil of our future growth.”
—Henry David Thoreau (1817–1862)
“The point of the dragonfly’s terrible lip, the giant water bug, birdsong, or the beautiful dazzle and flash of sunlighted minnows, is not that it all fits together like clockwork--for it doesn’t ... but that it all flows so freely wild, like the creek, that it all surges in such a free, finged tangle. Freedom is the world’s water and weather, the world’s nourishment freely given, its soil and sap: and the creator loves pizzazz.”
—Annie Dillard (b. 1945)