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What are the rates and types of weathering Mechanical and Chemical Weathering Mechanical Physical Weathering A rate of weathering where rocks are broken down physically The overall makeup of the rock stays the same Mostly common in cold dry climates Chemical Weathering Complex process by which rock components and internal structures of minerals are broken down converting the constituents into new minerals and releasing them into surrounding areas What affects weathering Surface Area Related to particle size controls weathering because the smaller the particle size the larger the surface area exposed to weathering for a given volume of material The presence of joints therefore increases a rock s surface area Spheroidal weathering which produces rounded surfaces on weathered rock can be caused where Concentric shells of altered rock material clay produced by chemical weathering are easily removed Faster weathering of edges and corners of rock tends to produce rounded surfaces where a sphere has the least volume to surface area ratio of any geometric form Climate controls weathering in that rocks experience the most thorough and rapid chemical weathering in warm humid climates Weathering rates are lowest in desert and cold climates Parent Material mineral composition of rock controls weathering processes because minerals that forms at high temperature and high pressure are less stable at the Earth s surface than low temperature low pressure minerals Bowen s Reaction Series can be used in reverse to predict the ease of chemical weathering of common igneous minerals Presence of Plants and Animals influence weathering as chemical and physical weathering rates are increased by the action of plants and animals Topography affects weathering as irregular steep topography exposes more rock to weathering than horizontal surfaces What are three things that effect the rate of weathering Rock characteristics Climate Differential weathering Definition of soil in terms of the ClORPT equation Soil is a function of climate organisms relief parent material and time regolith The layer of loose rock resting on bedrock constituting the surface of most land Partially weathered rock overlying bedrock The layer of unconsolidated rock and mineral fragments and soil that covers most of the land surface pedon Column of soil extending from the O horizon into the C horizon ped naturally occurring clump of soil column of soil extending from the O horizon into the C horizon the basic sampling unit used in a soil survey Horizonation occurs because water flow through biological and chemical reactions occur over time degree of B horizon development indicates maturity of soil Process of horizon development layers of soil that are formed over a period of time a layer of soil approximately parallel to the soil surface with characteristics produced by soil forming processes Field approach to horizons Color most diagnostic Texture of sand slit and clay Structure how well developed the soil is Boundries if they are ragged and have cracks in them that means some erosion has taken place Mottles fluctuating water table mottled refers to a patchy blotch texture of alteration or interbedding commonly found in limestone Krotovina Russian animal burrows What are the properties of soil profiles A E B C R Horizons A top soil Topmost inorganic horizon non carbon based E eluvial later Eluvial Zone zone of loss some material is lost from this area leached out We do not have this layer B subsoil Illuvial Zone the zone of gain C unconsolidated regolith The parent like material Is not parent material because something has altered it such as water or roots moving through it We don t have this layer R bedrock Hard bedrock like basalt granite or sandstone Not considered soil material Impossible to dig with hands Consolidated Parent material A the top The one that is exposed to the most intense weathering vulnerable to temrature changes Instance weathering E white All of the organic has been leached out of it such as the iron and the aluminum leached horizon B subsoil accumulation products of weathering Increasing clay its red C unconsolidated regolith Unchanged or slightly changed parent material sediments R hard bedrock like sandstone limestone shale Impossible to dig with hands Consolidated Parent material K increases in calcium carbonated in soil horizon Thick calcium carbonate horizon associated with deserts and dry environment bc not enough water circulation down through the soil profile to leach out the calcium carbonate Well Cemented carbonate horizon Distribution of Pedalfers and Pedocals across the continent Pedalfers east forest soils Pedocals west prairie soils What are alfisols Alfisols are moderately weathered soil beneath humid temperate forests comprised of a moderate organic layer and high amounts of clays in the B horizon Seasonal mid latitude soil Fertile strong clay rich Forest Soils Sandstone What are some features of aridisols arid dry low organic matter content calcite often forms in B horizon high pH dry soils salinization common Dessert Soils What are mollisols Mollisols are grassland soils of the steppes prairies It is noticeably dark soil with high amounts of organic material clay rich and well structured Parent material in our region Limestone Dense biomass produces dark A horizons Strong clay rich Grassland Soils Limestone Shale bedrock high clay content alcoholatic good preservation Primary vegetation is grass prairie soil What are vertisols Vertisols are heavy clay soils that contain more than 30 swelling clays which swell significantly when saturated and shrink significantly when dried Located in floodplains and are adjacent to drainages High in Calcium Clayey soils with wide cracks at some time of the year Floodplain Soils Truning soil being inverted A lot of contaction and expansion Parent material Clays that are along flood place of rock outcroppings that are sedimentary 75 How are ancient environments reconstructed Primary structures are looked at Examples cross bedded sand indicate sanddones primary structure examples of it sanddones eolian word used to describe the action of wind What are the three basic types of sedimentary rock How are Sedimentary Rocks Classified On the basis of their texture and Composition Texture and composition size and shape What are the common types of cements And how do we test for them Hemotite streak plate Limotite Streak Quartz scratch glass iron oxide calcium carbonate

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UNT GEOL 1610 - Lecture notes

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