111-16 - GY 111 Lecture Notes D Haywick(2008-09 1 GY 111 Lecture Note Series Soils Lecture Goals A What is soil B Typical soil profile(s C Soil

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GY 111 Lecture Notes D. Haywick (2008-09) 1 GY 111 Lecture Note Series Soils Lecture Goals A) What is soil? B) Typical soil profile(s) C) Soil Types Reference: Press et al., 2004, Chapter 7; Grotzinger et al., 2007, Chapter 16 p 373-384 A) What is Soil? As we discussed last time, rocks exposed at the surface of the Earth are subject to physical and chemical weathering. Given sufficient time and a suitable climate (hot and wet is best for chemical weathering; cold and wet is best for physical weathering), even the most resistant rock will be reduced to a shadow of its former self. The product of weathering will ultimately be sediment (the major ingredient of sedimentary rock); however, we reserve the term “sediment” for material that is moved from its place of origin (i.e., the place where weathering is occurring), to some depositional sink (i.e., a place where sediment is collected). In situ weathering of rock may leave a layer of weathered residue atop the rock. If the residue is more or less broken bits of rock which was primarily the result of physical weathering, we generally refer to it as regolith. If the rock has been physically and chemically weathered and if there is an appreciable amount of organic material, it is better to refer to the layer as soil: Soil is the most important Earth resource that we have (with the possible exception of water and as one smart ass student said "air"). Without soil, we would not have potatoes, lettuce, peas, corn, bread, beef, chickens, trees etc. Life without potatoes would be pretty tough. It is for this reason that soil conservation is taken so seriously. In the past, we had many serious experiences with soils erosion (the Great Dust Bowl of the early 20 th Century is but one example). Today, agricultural practices are better and soil erosion by wind is not as much of a problem; however, water runoff as a cause of soil erosion is still a major concern. B) Soil Profile(s) Soils are complex, but they all more or less share one important characteristic. They are layers. Soil scientists (usually agricultural geographers) recognize 3 or 4 layers (properly termed horizons ) within most soils. The following cartoon summarizes a typical soil profile:
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GY 111 Lecture Notes D. Haywick (2008-09) 2 The horizons are labeled from top to bottom, A (including O), B and C. The A Horizon is also called the Zone of Leeching and is the part of the soil that is most intensely chemically weathered. The term leaeching implies that all of the soluble minerals have been removed
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This note was uploaded on 02/04/2012 for the course GLY 111 taught by Professor Haywick during the Fall '11 term at S. Alabama.

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111-16 - GY 111 Lecture Notes D Haywick(2008-09 1 GY 111 Lecture Note Series Soils Lecture Goals A What is soil B Typical soil profile(s C Soil

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