03-Sed Production ppt - WEATHERING AND SEDIMENTARY ROCKS...

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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 - __the 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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03-Sed Production ppt - WEATHERING AND SEDIMENTARY ROCKS...

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