GEO 102 1st Edition Lecture 15 Outline of Last Lecture I. Half-livesOutline of Current Lecture II. Physical WeatheringIII. Chemical WeatheringIV. ErosionV. Environments of DepositionCurrent LectureTypes of Physical Weathering- Frost wedging- ice gets into a crack of a rock, expands, and breaks the rock- Unloading- exfoliation- Biological- from tree roots and fungi- Current/glacial- Thermal effectsTypes of Chemical Weathering- Dissolution- dropping acid o minerals. It dissolves the mineral away- Hydrolysis- electrochemically plucking molecules of a mineral out of the mineral- Oxidation- oxygen displacing a portion of the molecules in metal rich rocko Clays do not form initially as clay. Clay minerals only form as the residual broken down stuff of another mineral breaking downErosion- The transport of materials weathered from a rock- The principle agents are:o Liquid water (the most common)o Ice (rare but very effective)o Wind (only small particles)EntrainmentThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- This refers to the act of lifting a particle from a position of rest to be carried in a wind or current- We can predict how this will happen with great precision using mathOrder of Transport- Heavy particles need a lot of energy to lift and carry- Clay needs a lot of energy to lift (van der waals forces) but very little to carry it- Particles are lifted in the following order:o Silt, sand, pebbles, and clay last- But they are dropped in a different ordero Pebbles, sand, silt, and clayWhy is the Beach Sandy?- This illustrates why different sediments are found in different places- This is also a way we can know what past earth environments were likeo Depositional environmentso Certain rocks are associated with eachErosion Methods- High energy versus low energyo Ice is slow but viscous, so it is high energyo Wind is fast but not viscous, so it is low energyo Water is the most common carrier- Remember that the particles get further eroded as they travel and become smaller and rounderEnvironments of Deposition- Energy also defines where things drop outo Beaches have lots of wave energyo It washes away the small particles (sometimes even sand)o Leaving only the heavy materials behind Example: mud puddles and gold
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