03_416M_Sed Production_handout

03_416M_Sed Production_handout - WEATHERING AND SEDIMENTARY...

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1 WEATHERING AND SEDIMENTARY ROCKS 1.Weathering – The first step in the chain of processes that produce sedimentary rocks. Process which acts at the earth's surface to decompose and breakdown rocks. 2.Erosion movement of weathered material from the site of weathering. Primary agent is gravity , but gravity acts in concert with a fluid (water or air).
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2 Types of Weathering 1. Mechanical or Physical - the breakdown of rock material into smaller and smaller pieces with no change in the chemical composition of the weathered material. 2. Chemical - the breakdown of rocks by chemical agents (e.g., water). The rock material is changed into another substance by reacting with a chemical. Physical weathering breaks rocks down into smaller pieces thus increasing the surface area over which chemical weathering can occur (see below) . Estimates of Relative Contributions : Mechanical Weathering: 5.6×10 15 g/yr Chemical Weathering: 4.0×10 15 g/yr Roughly equal, but not evenly distributed over earth surface.
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3 1. Physical Weathering Most significant in: Cold, High relief areas Composition parent rock influences sediment production rate Some Physical Weathering Processes . Frost (Freeze-Thaw) Weathering - Water freezes and expands because the solid occupies greater volume . Action wedges the rocks apart. Temperature must move back and forth over freezing point . Insolation
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This note was uploaded on 02/08/2011 for the course GEO 416M taught by Professor Staff during the Fall '08 term at University of Texas at Austin.

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03_416M_Sed Production_handout - WEATHERING AND SEDIMENTARY...

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