UNIVERSITY OF SOUTH ALABAMA Last Time wow GY 111 Physical Geology Lecture 17 Groundwater Sedimentary Environments Part 2 1 Types of modern beaches beach morphology 2 Waves and beach dynamics 3 Shelves Biochemical and Chemical Rocks 4 Reefs atolls and oolites 5 Evaporites and evaporate basins 6 Deep Marine Environments Beach Morphology The Shelf The shallow marine flat area surrounding continents The Shelf Coral Reefs Atolls are isolated coral reefs that form on shelves or in much deeper water Ooid formation 1 Today Evaporite Basins If evaporation is extreme shallow sea water e g in tidal flats can completely dry up precipitating dissolved salts These areas are called evaporite basins or sabkhas Hydrosphere Groundwater 1 The hydrosphere and the hydrological cycle 2 Groundwater concepts 3 Groundwater topography Karst Web notes 17 Hydrological Cycle Water in the hydrosphere is circulated within the hydrological cycle The hydrosphere is defined as all the water above on and in the Earth hydrosphere http www coloradocollege edu dept ev courses EV211WWW hydrological 20cycle jpg Hydrological Cycle Groundwater Groundwater is water that infiltrates below the Earth s surface Most of the planet s water is in the oceans 96 followed by the ice caps 3 and then groundwater 1 Porosity percent void space in a material Permeability degree of connectivity of pores ability of a material to transmit a fluid http www coloradocollege edu dept ev courses EV211WWW hydrological 20cycle jpg Common permeable geological material includes sandstone limestone marble fault breccia http www belmont sd62 bc ca teacher geology12 photos erosion water permeability gif 2 Water Table Water Table Undersaturated zone Vadose Straight down water movement Saturated zone Phreatic Lateral water movement The water table is a planar surface that separates the saturated and undersaturated zones The water table is a planar surface that separates the saturated and undersaturated zones http myweb cwpost liu edu vdivener notes water table gif http myweb cwpost liu edu vdivener notes water table gif Water Table Morphology z The water table is a subdued replica of the overlying topographic surface Water Table Morphology z Where the water table intersects the surface there will be a water discharge spring pond lake or stream http earthsci org education teacher basicgeol groundwa chwattab gif http earthsci org education teacher basicgeol groundwa chwattab gif Water Table Morphology z Porous layers that are capable of passing water and releasing it at springs and or wells are called aquifers Water Table Morphology z Clay layers may act as aquicludes and generate a perched water table a localized water table http www tol ca files web images engineering environment WebImages unconfined jpg 3 Water Table Morphology z The recharge area is where the precipitation enters the groundwater system Types of Aquifers z z z z z Unconfined Aquifer open to direct recharge at the Earth s surface Confined Aquifer bracketed by aquicludes impermeable Potentiometric Surface elevation to which the pressurized water in a confined aquifer will rise Artesian Well water rises to an elevation above the aquifer Flowing Artesian Well Spring potentiometric surface is above the ground surface http groundwater oregonstate edu sites default files u1 rechargeb gif Types of Aquifers Potentiometric Surface elevation to which the pressurized water in a confined aquifer will rise Artesian Well water rises to an elevation above the aquifer Flowing Artesian Well Spring potentiometric surface is above the ground surface Anthropogenic Effects z Pumping lowers the elevation of the local water table Drawdown http www douglas co us water images Denver Basin Aquifers clip image004 jpg Anthropogenic Effects z Excessive pumping can severely lower the elevation of the local water table cone of depression Anthropogenic Effects z Which can really be bad during droughts wells run dry http myweb cwpost liu edu vdivener notes 4 Water Resources z Potable groundwater is a rapidly diminishing resource Other Groundwater Issues z Ground subsidence and collapse Sinkholes Other Groundwater Issues z Saltwater intrusion Salt water is more dense than fresh water Other Groundwater Issues z Contamination Issues z z z z Lead Pb sources include atmospheric pollution and older lead pipes Radioactive Waste natural and anthropogenic sources Microorganisms sewage and waste water flooding and storm surge Other chemical contaminants solvents gasoline nitrates road salt etc Contamination of groundwater supply Hydrothermal Systems z Groundwater heated by magmatic sources 5 Karst Topography Karst Topography z Limestone dissolution features are abundant and diverse both at the surface and underground zLike meandering rivers the degree of karstification can be related to age Karst Topography Small Scale rillenkarren karren solution pits pavements Karst Topography Large Scale caves sinkholes disappearing streams tower karst http www devsys co uk Album Places 20of 20Interest limestone 20caves jpg Karst Topography Large Scale Karst Features on Maps Caves caves sinkholes disappearing streams tower karst 6 Groundwater Flow Hydrogeology z Darcy s Law governs the volume of groundwater produced at a well head Q A K x h l z z z z z Q is volume A is cross sectional area of aquifer K is permeability h is hydraulic head i e you can determine groundwater flow rates l is map distance Today s Homework Download and read Web Lecture 17 Assignment 2 Groundwater Contour Maps 1 2 due next Tuesday Next Time 1 Geological Time 7
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