EAR 105 1st Edition Lecture 8Outline of Last Lecture I. Review of Rock CycleII. Introduction to Metamorphic RocksIII. Foliation & Non-FoliationOutline of Current Lecture IV. Review of TerminologyV. WeatheringVI. SoilCurrent LectureIV. Review of Terminology- Recall: sun’s energy drives Earth’s external processeso The sun’s energy thus drives the circulation of these processes- Weathering: the disintegration and decomposition of material at or near the surfaceo i.e. “breaking down in place”- Mass Wasting: the downslope movement of Earth materials due to gravity- Erosion: transport of Earth materials by water, wind, or iceo ex. Colorado river cuts down, or erodes, the layers of sedimentary rocks near in the Grand Canyon.o Where the sediment rocks wear down in place, weathering is occurringo Rivers can undercut sediment banks, which leads to processes of mass wasting V. Weathering- Two types of weathering: Mechanical (Physical) and Chemical- Mechanical weathering: breaking down into smaller pieceso Frost wedging- water gets into the cracks of rocks, expands as it freezes, and pushes the cracks out furthero Salt crystal growth- o Sheeting- rocks that are formed at depths are habituated to high temperature& pressure. Tectonic processes causes such rocks to be exposed at the surface, and the rocks must adjust to the environment through expansion, or unloading. The expansion and release of pressure results in the formation of cracks.These 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.o Biological Activity- animals interacting with rocks on the earth’s surface- Mechanical weathering facilitates further mechanical weathering as well as chemical weathering in that the former produces more surface area in which both types of weathering can occur- Chemical weathering: altering chemical composition (internal structure) of minerals by removing or adding elements-- necessarily occurs in placeo Water is the most important agent of chemical weathering; it is known as theuniversal solvent Oxygen dissolved in water oxidizes minerals, resulting in rust. Carbon dioxide dissolved in water forms carbonic acid and alters the material involvedo Chemical Weathering of Granite: Weathering of potassium feldspar produces clay minerals, soluble salt ( potassium bicarbonate), and silica in solution- I.e. the resulting clay minerals can undergo lithification to become shale, the most abundant sedimentary rock the quartz in granite is highly resilient to weathering- Mechanical and chemical weathering necessarily work together.- Spheroidal Weathering: occurs on the outside of the rock, resulting in the rounding of edges that were preliminarily left in angular shapes due to processes of mechanical weathering.- Important characteristics for determining a substances’ propensity to weathering Mineral composition and solubility Amount of joints, cracks, and edges Climate—since water plays such a big role in weathering processes- Temp and moisture- Differential weathering: caused by variations in compositiono Different driving forces of weathering can act at different rates depending on the subject material’s compositiono Where rock is more resistant, it will remain standingVI. Soil- Advanced breakdown of rocks and minerals results in the formation of soil- Soil is an interface in the Earth system—has biological components, air, water, and rock & mineral particles- Soil definition: a mixture of mineral matter, water, and airo Regolith: preliminary condition to soil—layer of broken down rock that coversthe Earth, but it is not yet soil since it cannot yet sustain plant life- Soil texture and structure: - Texture refers to the proportions of different particles- Structure: chemical composition- Residual Material: forms from the bedrock (parent material)- Transported soil: generally good soil, well sorted, has been transported by movement of water, wind, ice- Slope matters: o Very steep grounds don’t give room for soil to accumulate. The soils here are subject to mass wasting & erosiono Flood plains produce best soils, adequate moisture, room for accumulation- Horizons of soil based on temperature regions: the top four layers are considered true soilo Topsoil: O- Organic matter A- organic and mineral mattero Transitory E- little organic mattero Subsoil B- accumulation of clay and