Spring, Well, Caverns, and Geysers
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- SPRING,WELL,CAVERN andGEYSERS
- SPRINGA spring is a location where groundwaternaturally emerges from the Earths subsurfacein a defined flow and in an amount largeenough to form a pool or stream-like flow.Springs can discharge fresh groundwater eitheronto the ground surface, directly into the bedsof rivers or streams, or directly into the oceanbelow sea level.
- HOW SPRINGS F ORMMost of the water that emerges at springs is meteoric innature: that is, it originally fell as rain or snow on thesurface of the Earth. At hot springs near active volcanoes,some of the water may have originated from magma,molten rock that also contains dissolved substances suchas water. As magma cools and crystallizes in the Earthscrust, it releases much of this water. Spring water alsocan be ancient sea water, although it usually is dilutedwith meteoric water.
- springs is simple.It consists of: A recharge area where water enters the subsurface; An aquifer or set of aquifers through which the waterflows; and A discharge point where water emerges as a spring.
- C HARACTERISTICS OF SPRINGSSprings may be considered curious featuresbecause water appears to flow directly out ofrocks. Yet springs are less mysterious when oneunderstands where the water came from andhow long it has been in the subsurface.
- Origin of the Water. The question of where the water came from is specificallyasking from what region the water originatescommonly termedthe recharge area. The recharge area is usually, but not always,surrounded or outlined by topographic highs such as ridges andmountaintops. It is within the recharge area where the water,generally from precipitation, sinks below the surface and travels tothe spring.
- AGE OF THE WATER.Water ages can be estimated with chemical tracers ,provided the chemical behavior of tracers in thesubsurface is known. One example of a useful tracer istritium, a radioactive form of hydrogen. Tritium decaysradioactively to helium at a known rate. By measuring therelative abundance of tritium and helium produced bythe decay of tritium, it is possible to determine the age ofthe water.
- TEMPERATURE The temperature of spring water is related to the amount and rate ofgroundwater flow. As depth below the Earths surface increases,temperature increases. As a result, deep circulating groundwater can bewarmed. If groundwater velocities are low and the springs are small,most of the heat will be conducted though the rocks and the water willremain cold. If the springs are large, the spring water also will be coldbecause the volume of water is too great to be adequately warmed. Thewarmest springs occur when discharges are moderately large, and oftenare found in regions where the subsurface is unusually warm, such asvolcanically active areas.
- WELL..A water well is an excavation or structure created in theground by digging, driving, boring or drilling to accessgroundwater in underground aquifers. The well water isdrawn by an electric submersible pump, a trash pump, avertical turbine pump, a handpump or a mechanicalpump (e.g. from a water-pumping windmill). It canalso be drawn up using containers, such as buckets, thatare raised mechanically or by hand.
- TYPES OFWELLS..
- Dug wells Hacking at the ground with a pick and shovel is one way to dig awell. If the ground is soft and the water table is shallow, then dugwells can work. Historically, dug wells were excavated by handshovel to below the water table until incoming water exceeded thediggers bailing rate . The well was lined with stones, brick, tile, orother material to prevent collapse, and was covered with a cap ofwood, stone, or concrete. They cannot be dug much deeper thanthe water table -- just as you cannot dig a hole very deep when youare at the beach... it keeps filling up with water!
- Driven wells Driven wells are still common today. They are built bydriving a small-diameter pipe into soft earth, such as sandor gravel. A screen is usually attached to the bottom ofthe pipe to filter out sand and other particles. Problems?They can only tap shallow water, and because the sourceof the water is so close to the surface, contaminationfrom surface pollutants can occur.
- Drilled wells Most modern wells are drilled, which requires a fairlycomplicated and expensive drill rig. Drill rigs are oftenmounted on big trucks. They use rotary drill bits thatchew away at the rock, percussion bits that smash therock, or, if the ground is soft,large auger bits. Drilledwells can be drilled more than 1,000 feet deep. Often apump is placed at the bottom to push water up to thesurface.
- A cave or cavern is a natural underground spacelarge enough for a human to enter. Caves formnaturally by the weathering of rock and theyoften extend deep underground. The word"cave" can also refer to much smaller openingssuch as sea caves, rock shelters, and grottos.
- T Y P E S A N D F O R M AT I O NSolutional caveare the most frequently occurring caves and such caves form inrock that is soluble, such as limestone, but can also form in otherrocks, including chalk, dolomite, marble, salt, and gypsum. Rock isdissolved by natural acid in groundwater that seeps throughbedding-planes, faults, joints and so on. Over geological epochscracks expand to become caves or cave systems.
- Primary caveSome caves are formed at thesame time as the surrounding rock.These are sometimes calledprimary caves
- SEA CAVE OR LITTORAL CAVE Sea caves are found along coasts around the world. A specialcase is littoral caves, which are formed by wave action in zones ofweakness in sea cliffs. Often these weaknesses are faults, but theymay also be dykes or bedding-plane contacts. Some wave-cut cavesare now above sea level because of later uplift. Elsewhere, in placessuch as Thailands Phang Nga Bay, solutional caves have beenflooded by the sea and are now subject to littoral erosion. Sea cavesare generally around 5 to 50 metres (16 to 160 ft) in length, but mayexceed 300 metres (980 ft).
- GL ACIER CAVE Glacier caves occur in ice and under glaciers and areformed by melting. They are also influenced by the veryslow flow of the ice, which tends to close the caves again.(These are sometimes called ice caves, though this termis properly reserved for caves that contain year-round iceformations).
- A geyser is a spring characterized by intermittent dischargeof water ejected turbulently and accompanied by a vapourphase (steam). The word geyser comes from Geysir, the nameof an erupting spring at Haukadalur, Iceland; that name, inturn, comes from the Icelandic verb geysa, "to gush. Theformation of geysers is due to particular hydrogeologicalconditions, which exist in only a few places on Earth, so theyare a fairly rare phenomenon. Generally all geyser field sites arelocated near active volcanic areas, and the geyser effect is due tothe proximity of magma.
- F ORM AND FUNCTION Geysers are temporary geological features. Geysers aregenerally associated with volcanic areas.As the water boils, theresulting pressure forces a superheated column of steam andwater to the surface through the geysers internal plumbing.The formation of geysers specifically requires the combinationof three geologic conditions that are usually found in volcanicterrain.
- Intense heat The heat needed for geyser formation comes from magmathat needs to be near the surface of the earth. The fact thatgeysers need heat much higher than normally found near theearths surface is the reason they are associated with volcanoesor volcanic areas. The pressures encountered at the areas wherethe water is heated makes the boiling point of the water muchhigher than at normal atmospheric pressures.
- Water The water that is ejected from a geyser must travel undergroundthrough deep, pressurized fissures in the Earths crust.A plumbing system In order for the heated water to form a geyser, a plumbingsystem is required. This includes a reservoir to hold the water whileit is being heated. Geysers are generally aligned along faults. Theplumbing system is made up of a system of fractures, fissures,porous spaces and sometimes cavities. Constrictions in the systemare essential to the building up of pressure before an eruption.
- GENERAL C ATEGORIZATION Old faithful geyseror cone geyserErupts approximately91 minutes
- Fountain geysererruptingFrom the pool
- END OF SLIDESHOW..tnxLynnette joy Ulep4bse3_soc.sci