GEO 303 Lecture Notes - Lecture 7: Geode, Breccia, Natural Bridge Caverns
10 May 2016
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Classified by the way they form: sedimentary rock: form from sediments. Sedimentary rocks: formed by the deposition, compaction, and cementation of sediments or chemical or biochemical precipitation, typically occur at or relativity close to the surface (low pressure and temperature, 1. Clastic: made of sediments that come from pre existing rocks that have been weathered and eroded then glued together (lithified: 2. How are sediments produced: weathering: chemical/physical breakdown of rock at or near earth"s surface. Mechanical weathering: wind, abrasion by flowing water, pressure change (exfoliation), roots/burrows, frost wedging, wetting/drying. Frost wedging: water goes into cracks during summer, freezes during winter, expands, pushes it apart. Chemical weathering: reacting between minerals and water to form new minerals and/or dissolved ions. Exfoliation: like an onion, comes off in sheets or layers. Weathering process: some minearls are more resistant to weathering than others. Minerals that form at high temperature have low stability. Minerals that form at the surface (low temp) have high stability.
