Weathering+and+Erosion

2Weathering The breakdown of rocks at of near the surface of the Earth Physical Weathering The breakdown of rocks into smaller pieces without chemical change Ice wedging (frost action) Water held in the cracks of rocks wedges the rock apart when it freezes Root wedging (plant action) Tiny roots grow into cracks in the rock and then as the root grows the rock splits Exfoliation When large masses of rocks, mainly igneous, are lifted up to the surface the relief of overlying pressure causes the rock to expand. Upward expansion leads to curved breaks which may peel off in layers. Chemical Weathering The breakdown of rock through a change in mineral or chemical composition Oxidation: The chemical reaction of oxygen with other substances. Iron is most easily attacked resulting in rust (iron oxides) Carbonic Acid When carbon dioxide dissolves into water. It dissolves many common minerals. <span style="font-family: Verdana,Geneva,sans-serif;">Minerals Resistance To Weathering <span style="font-family: Verdana,Geneva,sans-serif;">Different minerals and rocks have different physical and chemical properties which allow them to weather at different rates <span style="font-family: Verdana,Geneva,sans-serif;">Quartz <span style="font-family: Verdana,Geneva,sans-serif;">Almost unchanged by chemical weathering. It is hard and does not have cleavage so it also resists mechanical weathering <span style="font-family: Verdana,Geneva,sans-serif;">Feldspar, mica,calcite and gypsum <span style="font-family: Verdana,Geneva,sans-serif;">Affected by both types of weathering and will break down into clay with calcite and gypsum dissolving and begin carried off in solution <span style="font-family: Verdana,Geneva,sans-serif;">Sedimentary Rocks: <span style="font-family: Verdana,Geneva,sans-serif;">Shale is the least resistant to mechanical weathering <span style="font-family: Verdana,Geneva,sans-serif;">Sandstone: is the most resistant to mechanical weathering <span style="font-family: Verdana,Geneva,sans-serif;">The type of cement which hold the sandstone together determines how resistant the rock is calcite- low resistance Silica-high resistance <span style="font-family: Verdana,Geneva,sans-serif;">Rocks which contain the mineral calcite, such as limestone or marble are somewhat resistant to mechanical weathering but is the least resistant to chemical weathering <span style="font-family: Verdana,Geneva,sans-serif;">Factors affecting rate of weathering <span style="font-family: Verdana,Geneva,sans-serif;">Exposure: <span style="font-family: Verdana,Geneva,sans-serif;">The closer to the surface of the earth, the faster it will weather <span style="font-family: Verdana,Geneva,sans-serif;">Rate and type of weathering depends on exposure of rocks to air, water and the action of living things <span style="font-family: Verdana,Geneva,sans-serif;">Surface Area: <span style="font-family: Verdana,Geneva,sans-serif;">The grater the surface area exposed to weathering the faster the rate of weathering <span style="font-family: Verdana,Geneva,sans-serif;">Two samples of the same material having the same mass can have different surface areas. If one sample is a large piece of marble with a mass of 50g and the other 50g of many small pieces of marble the smaller pieces will have the greater surface area <span style="font-family: Verdana,Geneva,sans-serif;">Climate Effect on Weathering <span style="font-family: Verdana,Geneva,sans-serif;">Chemical weathering is usually greater in Warm, moist climates physical weathering is usually greater in Moist areas with temperature variations (cold and warm)

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<span style="font-family: Verdana,Geneva,sans-serif;">Soils <span style="font-family: Verdana,Geneva,sans-serif;">Soil is made of loose weathered rock and organic material in which plants with roots can grow, The rocks material is composed of sand, silt and clay. <span style="font-family: Verdana,Geneva,sans-serif;">Parent material is the material from which a soil is formed <span style="font-family: Verdana,Geneva,sans-serif;">Residual soil- soil that has the bedrock beneath the soil as a parent material <span style="font-family: Verdana,Geneva,sans-serif;">Transported Soil- Soils formed from deposits left by winds,rivers and glaciers <span style="font-family: Verdana,Geneva,sans-serif;">A-horizon top soil <span style="font-family: Verdana,Geneva,sans-serif;">Darkest color due to organic material <span style="font-family: Verdana,Geneva,sans-serif;">B-hoizon subsoil <span style="font-family: Verdana,Geneva,sans-serif;">1) clay is washed to the subsoil <span style="font-family: Verdana,Geneva,sans-serif;">2) may contain soluble minerals such as calcium <span style="font-family: Verdana,Geneva,sans-serif;">3) color is usually red-brown from Iron oxides that form above and wash down <span style="font-family: Verdana,Geneva,sans-serif;">C- Horizon <span style="font-family: Verdana,Geneva,sans-serif;">Made of slightly weathered parent material (rock fragments) <span style="font-family: Verdana,Geneva,sans-serif;">Climate: <span style="font-family: Verdana,Geneva,sans-serif;">Tropical soils from in areas with high temperatures and heavy rainfall. A thick infertile soil profile are results of heavy rain. <span style="font-family: Verdana,Geneva,sans-serif;">Grassland soil form in areas with enough rainfall for heavy grass, but not trees. About 1 meter thick and fertile <span style="font-family: Verdana,Geneva,sans-serif;">Forest soils form in humid regions with cool seasons. Soil profile is less then 1 meter thick with well developed A,B and C horizons <span style="font-family: Verdana,Geneva,sans-serif;">Desert soils form in very dry climates. Soil profile is a few centimeters thick and be very fertile when they are warted <span style="font-family: Verdana,Geneva,sans-serif;">Arctic soils form at high elevations and high latitudes. Poorly drained surfaces and the bottom layers are constantly frozen <span style="font-family: Verdana,Geneva,sans-serif;">Mass Movements <span style="font-family: Verdana,Geneva,sans-serif;">Movements of loose earth material down a slope <span style="font-family: Verdana,Geneva,sans-serif;">A) Gravity is an aid in weathering and erosion. Steep slopes weather to gentle slopes. <span style="font-family: Verdana,Geneva,sans-serif;">Creep- slow, imperceptible down slope movement of the soil. Causes objects that are fixed in the soil to learn downhill. Water in the soil is what adds the weight <span style="font-family: Verdana,Geneva,sans-serif;">Mudflow- the rapid movement of a water saturated mass of soil. <span style="font-family: Verdana,Geneva,sans-serif;">Slump- Occurs when a section of land moves downhill as a whole because of a plane of weakness in the underlying soil. <span style="font-family: Verdana,Geneva,sans-serif;">Landslide- Sudden movement of a mass or bedrock or loose rock down the slope of a hill or mountain. (Avalanche, snow, ice, rock and soil) <span style="font-family: Verdana,Geneva,sans-serif;">Talus- Is a pile of rock fragments at the base of a cliff. <span style="font-family: Verdana,Geneva,sans-serif;">Wind Erosion <span style="font-family: Verdana,Geneva,sans-serif;">Wind transports materials by causing their particles to move in different ways <span style="font-family: Verdana,Geneva,sans-serif;">Suspension- a method of transport by which strong winds cause small particles to stay airborne long distances. <span style="font-family: Verdana,Geneva,sans-serif;">Salutation-Causes a bouncing of method of motion of larger particles. Salutation accounts for most sand transport <span style="font-family: Verdana,Geneva,sans-serif;">Wind erosion is greatest in Arid climates (low precipitation) with little vegetation Deserts and sea shores Abrasion is a process of erosion found in wind, water and ice. It occurs wen particles such as sand rub against they surface of rocks or other materials <span style="font-family: Verdana,Geneva,sans-serif;">Ventifacts are rocks shaped by windblown sediments <span style="font-family: Verdana,Geneva,sans-serif;">Wind deposition occurs in areas where wind velocity decreases <span style="font-family: Verdana,Geneva,sans-serif;">dunes are piles of windblown sand has have a gentle side and steep side <span style="font-family: Verdana,Geneva,sans-serif;">The gentler slope occurs when the side on which the wins is blowing (windward side). The steeper the slope occurs on the side projected from the wind (leeward side) <span style="font-family: Verdana,Geneva,sans-serif;">Loses-Thick deposits of fine lightweight particles(silt and clay) that are carried by the wind in great quantities of long distances.They are some of the most fertile soils. <span style="font-family: Verdana,Geneva,sans-serif;">Louis Agassiz is known for the idea that glaciers once covered many parts of the world <span style="font-family: Verdana,Geneva,sans-serif;">Formation of A glacier <span style="font-family: Verdana,Geneva,sans-serif;">Glaciers are accumulations of ice enough to survive summer melt- forms from snow under pressure which turns to ice <span style="font-family: Verdana,Geneva,sans-serif;">Snow line-The lowest level that permanent snows reach in summer <span style="font-family: Verdana,Geneva,sans-serif;">Highest near the equator <span style="font-family: Verdana,Geneva,sans-serif;">Fern is the Granular ice material formed in snow fields from freshly fallen snow become compressed and recrystallizing <span style="font-family: Verdana,Geneva,sans-serif;">The lower layers become ice and begin flowing downward or outward because of overlying pressure <span style="font-family: Verdana,Geneva,sans-serif;">Alpine Glaciers(valley glaciers) <span style="font-family: Verdana,Geneva,sans-serif;">Occur in mountain regions above the snow line <span style="font-family: Verdana,Geneva,sans-serif;">Flow downhill and carve out the U-shaped valleys <span style="font-family: Verdana,Geneva,sans-serif;">Continental Glaciers (ice sheets) <span style="font-family: Verdana,Geneva,sans-serif;">A glacier that spreads over a wide geographic area. Form in plan areas where the snow line is close to sea level and wide areas above the snow line(responsible for much of the landscape in NY) <span style="font-family: Verdana,Geneva,sans-serif;">20,00 years ago,new york state was covered by a huge ice sheet that originated in Canada <span style="font-family: Verdana,Geneva,sans-serif;">Glacier Movement <span style="font-family: Verdana,Geneva,sans-serif;">The overlying weight of snow and ice causes gains of ice partially melt and refreeze. As this happens ice grains slip past each other and move downhill <span style="font-family: Verdana,Geneva,sans-serif;">Glaciers move more rapidly at the surface than at the base and faster at the center than at the sides.Friction with the valley walls slow the flow. <span style="font-family: Verdana,Geneva,sans-serif;">*Flow at a rate of a few cm to several meters per day <span style="font-family: Verdana,Geneva,sans-serif;">Crevasses: Are cracks across the width of the glacier that form when glaciers move other steep slopes I<span style="font-family: Verdana,Geneva,sans-serif;">ce front is the end of a glacier <span style="font-family: Verdana,Geneva,sans-serif;">The ice front is Stationary as long as the rate of movement and melting are equal <span style="font-family: Verdana,Geneva,sans-serif;">A glacier recedes when it melts faster than normal <span style="font-family: Verdana,Geneva,sans-serif;">A glacier advances when the rate of movement is greater then the rate at which it melts <span style="font-family: Verdana,Geneva,sans-serif;">Calving is when blocks of ice break off into the sea <span style="font-family: Verdana,Geneva,sans-serif;">Pieces of rock are picked up as glaciers move and then are dragged along the bedrock and /or valley wall <span style="font-family: Verdana,Geneva,sans-serif;">Find sand acts as sandpaper and politic the bedrock <span style="font-family: Verdana,Geneva,sans-serif;">Larger sediments leave long parallel scratched called striations <span style="font-family: Verdana,Geneva,sans-serif;">striations show the direction of movement <span style="font-family: Verdana,Geneva,sans-serif;">The finger lakes of NY were formed as advancing ice deeply scoured out valleys <span style="font-family: Verdana,Geneva,sans-serif;">Glacial through are formed when a glacier carve out a valely forming a U-shaped valley <span style="font-family: Verdana,Geneva,sans-serif;">Valley glaciers leave sharp mountain tops while continental glaciers leave rounded tops <span style="font-family: Verdana,Geneva,sans-serif;">Here are a few depositionl features of glaciers <span style="font-family: Verdana,Geneva,sans-serif;">Moraine is Glacier deposit of unsorted rock material <span style="font-family: Verdana,Geneva,sans-serif;">Ground Moraine- Carried alond the bottom <span style="font-family: Verdana,Geneva,sans-serif;">Lateral Moraine-Long lines of Rocks iences along the valley slides <span style="font-family: Verdana,Geneva,sans-serif;">Medial Moraine-When two glaciers come together and there lateral moraines join together <span style="font-family: Verdana,Geneva,sans-serif;">Terminal Moraines- Piles of unsorted soil and rock left at the front of Glacier where it stopped moving. This marks the farthest advance of the glacier <span style="font-family: Verdana,Geneva,sans-serif;">Drumlins-Accumulations of rock and soil that build up in front if the ice as the ice moved up and over thesis over these piles <span style="font-family: Verdana,Geneva,sans-serif;">Round end faces the direction in which the glacier advance <span style="font-family: Verdana,Geneva,sans-serif;">Kettles-When buried ice left by a glacier melts and leaves a depression <span style="font-family: Verdana,Geneva,sans-serif;">Kettle Lake-When these depressions fill with water like a pond <span style="font-family: Verdana,Geneva,sans-serif;">Erosion is the process by whuch earth materials are moved by naturall agents like water,wind and ice <span style="font-family: Verdana,Geneva,sans-serif;">Running Water: <span style="font-family: Verdana,Geneva,sans-serif;">Running water is the most effective agent of erosion <span style="font-family: Verdana,Geneva,sans-serif;">The sun is where running water gets energy <span style="font-family: Verdana,Geneva,sans-serif;">Rocks are weathered both chemically and physically by running water <span style="font-family: Verdana,Geneva,sans-serif;">Physical <span style="font-family: Verdana,Geneva,sans-serif;">Abrasion is the term given to the use of sands,pebbles and even boulders as cutting tools to grind away at the stream bed. During this process the "tools" themselves wear down <span style="font-family: Verdana,Geneva,sans-serif;">Chemical: <span style="font-family: Verdana,Geneva,sans-serif;">The water dissolves soluble minerals <span style="font-family: Verdana,Geneva,sans-serif;">Rivers carry rock material in three ways <span style="font-family: Verdana,Geneva,sans-serif;">Solution- This is material that is dissolved form he bedrock. Most commonly found in solution are compounds are calcium and magnesium <span style="font-family: Verdana,Geneva,sans-serif;">Suspension- When small rock particles, such as clay silt and fine sand, are kept from sinking by the turbulence of the stream. This gives the water a muddy look <span style="font-family: Verdana,Geneva,sans-serif;">Bed Load- Sand, pebbles and some boulders which move along the stream bed. <span style="font-family: Verdana,Geneva,sans-serif;">Carrying power <span style="font-family: Verdana,Geneva,sans-serif;">Carrying power- is the indicated by both the total amount of sediment in a stream and by the size of the particles being moved <span style="font-family: Verdana,Geneva,sans-serif;">the stream discharge and speed will determine the carrying power of the stream <span style="font-family: Verdana,Geneva,sans-serif;"> Discharge is the volume of water flowing past a given point at a given time <span style="font-family: Verdana,Geneva,sans-serif;"> Speed is generally determined by the steepness or gradient of its bed <span style="font-family: Verdana,Geneva,sans-serif;"> A stream is moving at high speed discharge can carry much larger sediments then a slow moving stream. Example: spring time snow melting excessive rai. <span style="font-family: Verdana,Geneva,sans-serif;"> Rivers tent to have V-sjaped velley because they tend to flow a high speends and dig int the stream bed. <span style="font-family: Verdana,Geneva,sans-serif;"> Base level is the lowest level a river can cut into its bed to from a permanent stream rain water must flow down a slope and dig deep enough to cut into water table. This weathering away of the land to form a stream valley is called head ward erosion. <span style="font-family: Verdana,Geneva,sans-serif;"> A divide is an area of high land that separates one river valley from another <span style="font-family: Verdana,Geneva,sans-serif;"> On ethier side of a divide a river sytem may form <span style="font-family: Verdana,Geneva,sans-serif;"> Watershed is all of the land that drains into the river either directly of through its tributaries <span style="font-family: Verdana,Geneva,sans-serif;"> Waterfalls <span style="font-family: Verdana,Geneva,sans-serif;"> Water flowing over a steep cliff will result in a waterfall. Waterfalls are not permanent structures <span style="font-family: Verdana,Geneva,sans-serif;"> Undermining is the erosional process occurring at the base of a waterfall. Here water carrying sediment plunges down and back into the stream bed and cliff below. This causes the rocks t the top of the falls to overhand. Over time this overhand will collapse and the stream will move back towards its source <span style="font-family: Verdana,Geneva,sans-serif;"> River Deposition <span style="font-family: Verdana,Geneva,sans-serif;"> Deposition occurs when a stream either decreases in speed or discharge <span style="font-family: Verdana,Geneva,sans-serif;"> Generally the speed decreases when its slopes decrease or its bed widens. The greatest loss of speed occurs when a river empties into a quiet body of water <span style="font-family: Verdana,Geneva,sans-serif;"> A decrease in discharge would occur if a river traveled through an area with low precipitation <span style="font-family: Verdana,Geneva,sans-serif;"> As rivers begin to decrease their slope they over slower and will begin to move side to side <span style="font-family: Verdana,Geneva,sans-serif;"> As the valley wall on either side is eroded the valley floor is widen <span style="font-family: Verdana,Geneva,sans-serif;"> A flood plain is the widened valley floor area which will accumulate water during times of excess rain when the river floods <span style="font-family: Verdana,Geneva,sans-serif;"> Erosion and Deposition in a river <span style="font-family: Verdana,Geneva,sans-serif;"> endears are broad curves in the river (each bend or turn) <span style="font-family: Verdana,Geneva,sans-serif;"> Erosion is greatest on the outside of a meander where water is flowing the fastest. (cut bank) <span style="font-family: Verdana,Geneva,sans-serif;"> Erosion fast cut banks <span style="font-family: Verdana,Geneva,sans-serif;"> Deposition slow- fill bank <span style="font-family: Verdana,Geneva,sans-serif;"> Oxbow lake- meanders can only become so large before they break through into another meander. The river then deposits mud and silt along the end of the abandoned meander. The now separated meander becomes a lake. <span style="font-family: Verdana,Geneva,sans-serif;"> Running water deposts well sorted particles <span style="font-family: Verdana,Geneva,sans-serif;"> Vertical sorting when sediments are suddenly deposited into water. The particles separate by size with the largest on the bottom and smallest on top. <span style="font-family: Verdana,Geneva,sans-serif;"> Horizontal Sorting- when rivers empty their sediments into quiet bodies of water. Particles are sorted by size with larger particles being found closer to the shore and smaller particles being carried out into the body of water to be deposited <span style="font-family: Verdana,Geneva,sans-serif;"> Delta- A fan shaped deposit of sediment at the mouth of a river <span style="font-family: Verdana,Geneva,sans-serif;"> River vocabulary <span style="font-family: Verdana,Geneva,sans-serif;"> River Stages: <span style="font-family: Verdana,Geneva,sans-serif;"> Young river <span style="font-family: Verdana,Geneva,sans-serif;"> Slope of the land-Steep <span style="font-family: Verdana,Geneva,sans-serif;"> Velocity- fast <span style="font-family: Verdana,Geneva,sans-serif;"> Type of erosion-head ward erosion <span style="font-family: Verdana,Geneva,sans-serif;"> Shape of the Valley- straight <span style="font-family: Verdana,Geneva,sans-serif;"> Characteritics- channel touches both valley walls Valley is Vshaped <span style="font-family: Verdana,Geneva,sans-serif;">Examples-Upper hudson and Niagara river <span style="font-family: Verdana,Geneva,sans-serif;">Special Features- waterfalls,rapids, islands and no tributaries <span style="font-family: Verdana,Geneva,sans-serif;">Mature River: <span style="font-family: Verdana,Geneva,sans-serif;">Slope of the land-less steep <span style="font-family: Verdana,Geneva,sans-serif;">Velocity-slowing down <span style="font-family: Verdana,Geneva,sans-serif;">Type of Erosion- Lateral Erosion (widening the valley) <span style="font-family: Verdana,Geneva,sans-serif;">Shape of the valley- Meandering <span style="font-family: Verdana,Geneva,sans-serif;">Characteristic Features-Channel touches both valley walls on the meanders valley is wide and flat <span style="font-family: Verdana,Geneva,sans-serif;">Examples: Ohio and Mississippi rivers <span style="font-family: Verdana,Geneva,sans-serif;">Special features-oxbow lake,meanders, flood plain, tributaries <span style="font-family: Verdana,Geneva,sans-serif;">Old River <span style="font-family: Verdana,Geneva,sans-serif;">Slope of the land-nearly flat <span style="font-family: Verdana,Geneva,sans-serif;">Velocity-sluggish <span style="font-family: Verdana,Geneva,sans-serif;">Type of erosion- no erosion (depositing sediments) <span style="font-family: Verdana,Geneva,sans-serif;">Shape of the valley-very meandering <span style="font-family: Verdana,Geneva,sans-serif;">Characteristic features- Channel does not touch the valley walls and valley is very wide and flat <span style="font-family: Verdana,Geneva,sans-serif;">Examples-Lower Mississippi <span style="font-family: Verdana,Geneva,sans-serif;">Special Features- Flood plain,oxbow lakes,yazoo streams, back-swamps (bayous)
 * <span style="font-family: Verdana,Geneva,sans-serif;">Erosion: **

<span style="font-family: Verdana,Geneva,sans-serif;">Groundwater and Wells: <span style="font-family: Verdana,Geneva,sans-serif;">The Water Cycle: <span style="font-family: Verdana,Geneva,sans-serif;">The hydrosphere- <span style="font-family: Verdana,Geneva,sans-serif;">Water on and in earth's crust makes up hydrosphere <span style="font-family: Verdana,Geneva,sans-serif;">About 97% of the hydrosphere is contained in the oceans <span style="font-family: Verdana,Geneva,sans-serif;">Fresh water is about only 3% of the hudrosphere <span style="font-family: Verdana,Geneva,sans-serif;">The most fresh water (70-80%) is found in polar caps <span style="font-family: Verdana,Geneva,sans-serif;">Rivers, streams and lakes are only a small fraction of Earth's fresh water <span style="font-family: Verdana,Geneva,sans-serif;">Groundwater and precipitation <span style="font-family: Verdana,Geneva,sans-serif;">Oceans are the ultimate source of all water on earth <span style="font-family: Verdana,Geneva,sans-serif;">Evaporation of seawater cycles water into the atmosphere in from of invisible water vapor and visible clouds <span style="font-family: Verdana,Geneva,sans-serif;">Some of the precipitation falls back into the oceans and some back on land. <span style="font-family: Verdana,Geneva,sans-serif;">Infiltration: process which precipitation has fallen on land, trickles into the ground and becomes groundwater <span style="font-family: Verdana,Geneva,sans-serif;">Only a small portion of water becomes runoff and returns back to oceans through streams and rivers <span style="font-family: Verdana,Geneva,sans-serif;">The water slowly moves through the ground and eventually returns to the surface, though springs and seepage into wetlands and streams then back into the oceans <span style="font-family: Verdana,Geneva,sans-serif;">Groundwater storage <span style="font-family: Verdana,Geneva,sans-serif;">Puddles of water on the ground seep into small openings in the ground called pores. <span style="font-family: Verdana,Geneva,sans-serif;">Although the crust appears solid, it is composed of soil, sediment and rock that contains pore spaces <span style="font-family: Verdana,Geneva,sans-serif;">The amount of pore space in a material is called its porosity. <span style="font-family: Verdana,Geneva,sans-serif;">Subsurface materials have prosities ranging from 2 to more than 50% <span style="font-family: Verdana,Geneva,sans-serif;">Example: the porosity of well sorted sand is 30% however in poorly sorted sediment smaller particles occupy some of the pore spaces and reduce overall porosity of the sediment <span style="font-family: Verdana,Geneva,sans-serif;">Cement that binds grains of sedimentary rocks together reduces the rocks porosity <span style="font-family: Verdana,Geneva,sans-serif;">Because of enormous volume of sediments and rocks beneath the surface large quantity of groundwater are stored int eh pore spaces. <span style="font-family: Verdana,Geneva,sans-serif;">Zone of saturation and Aeration: <span style="font-family: Verdana,Geneva,sans-serif;">The zone of saturation- region below Earth's surface in which groundwaer fills all the pores <span style="font-family: Verdana,Geneva,sans-serif;">The upper boundary of the zone of saturation is called a water table <span style="font-family: Verdana,Geneva,sans-serif;">Only the water in the zone of saturation is called groundwater <span style="font-family: Verdana,Geneva,sans-serif;">The zone Aeration is above the water table. Materials are moist because they're not saturated with water. Air occupies most of the pores <span style="font-family: Verdana,Geneva,sans-serif;">Water Movement <span style="font-family: Verdana,Geneva,sans-serif;">The water in the zones of saturation and aeration is classified as gravational or capillary water <span style="font-family: Verdana,Geneva,sans-serif;">Graveitational water trickles downward as a result of gravity <span style="font-family: Verdana,Geneva,sans-serif;">Capillary water is drawn upward through capillary action above the water table and is held in pore spaces of rocks and sediments because of surface tension <span style="font-family: Verdana,Geneva,sans-serif;">Water table <span style="font-family: Verdana,Geneva,sans-serif;">The depth of a water table varies on local weather conditions <span style="font-family: Verdana,Geneva,sans-serif;">Swampy area's water table is at Earth's surface <span style="font-family: Verdana,Geneva,sans-serif;">The water table follows the shape of the land that is located about it. <span style="font-family: Verdana,Geneva,sans-serif;">The table fluctuates with seasonal and weather conditions <span style="font-family: Verdana,Geneva,sans-serif;">It rises in wet seasons (like spring) and drops during dry seasons,such as summer <span style="font-family: Verdana,Geneva,sans-serif;">Groundwater Movement <span style="font-family: Verdana,Geneva,sans-serif;">Groundwater flows downhill in the direction of which the table goes <span style="font-family: Verdana,Geneva,sans-serif;">The motion is slow becuase the water flows through many tiny pres <span style="font-family: Verdana,Geneva,sans-serif;">The tendency of material to let water through is it premeability <span style="font-family: Verdana,Geneva,sans-serif;">Materials with larger connected pores like sand and gravel have high premeability and high flows velocities <span style="font-family: Verdana,Geneva,sans-serif;">Permeable materials include high fractured bedrock sandstone and limestone <span style="font-family: Verdana,Geneva,sans-serif;">Groundwater flows through premeable sediment and rock called aquifers, where pore spaces are large and conected <span style="font-family: Verdana,Geneva,sans-serif;">Impermeable- fine-grained materials that have low premeability becuase of their small pores <span style="font-family: Verdana,Geneva,sans-serif;">Silt, clay and shale are all impremeable materials <span style="font-family: Verdana,Geneva,sans-serif;">Impermeable layers called aquicludes are barriers to ground water flow <span style="font-family: Verdana,Geneva,sans-serif;">Wells: <span style="font-family: Verdana,Geneva,sans-serif;">Wells are holes dug or drilled into the ground to reach an aquifer <span style="font-family: Verdana,Geneva,sans-serif;">There are two main types of wells, ordinary and artesian <span style="font-family: Verdana,Geneva,sans-serif;">Ordinary wells: simpest well are those that are dug or driled below the water table into an aquifer which is the same level water in the well as the sourrounding water table <span style="font-family: Verdana,Geneva,sans-serif;">As water is drawn out of the well it is replaced by surrounding water in the aquifer <span style="font-family: Verdana,Geneva,sans-serif;">Over-pumping occurs when water is drawn ot of a well at a rate faster than that at which is replaced <span style="font-family: Verdana,Geneva,sans-serif;">The diffrence between the original table and water level in pumed well is called drawndown <span style="font-family: Verdana,Geneva,sans-serif;">If many wells withdrawn water from table-aquifer cones of depression can over-lap and lowers table causing well to become dry <span style="font-family: Verdana,Geneva,sans-serif;">Water from precip replenishes water content of aquifer called recharge <span style="font-family: Verdana,Geneva,sans-serif;">Artesian Wells: when rate of recharge is high enough pressurized water in a well drilled