SPRING,WELL, CAVERN and GEYSERS…

SPRINGA spring is a location where groundwater naturally emerges from the Earth's subsurface in a defined flow and in an amount large enough to form a pool or stream-like flow. Springs can discharge fresh groundwater either onto the ground surface, directly into the beds of rivers or streams, or directly into the ocean below sea level.

H O W S P R I N G S F O R MMost of the water that emerges at springs is meteoric in nature: that is, it originally fell as rain or snow on the surface 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 such as water. As magma cools and crystallizes in the Earth's crust, it releases much of this water. Spring water also can be ancient sea water, although it usually is diluted with 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 water flows; andA discharge point where water emerges as a spring.

CHARACTERISTICS OF SPRINGS

Springs may be considered curious features because water appears to flow directly out of rocks. Yet springs are less mysterious when one understands where the water came from and how long it has been in the subsurface.

Origin of the Water.The question of where the water came from is specifically asking from what region the water originates—commonly termed the recharge area. The recharge area is usually, but not always, surrounded or outlined by topographic highs such as ridges and mountaintops. It is within the recharge area where the water, generally from precipitation, sinks below the surface and travels to the spring. 

AGE OF THE WATER.Water ages can be estimated with chemical tracers , provided the chemical behavior of tracers in the subsurface is known. One example of a useful tracer is tritium, a radioactive form of hydrogen. Tritium decays radioactively to helium at a known rate. By measuring the relative abundance of tritium and helium produced by the decay of tritium, it is possible to determine the age of the water.

TEMPERATUREThe temperature of spring water is related to the amount and rate of groundwater flow. As depth below the Earth's surface increases, temperature increases. As a result, deep circulating groundwater can be warmed. If groundwater velocities are low and the springs are small, most of the heat will be conducted though the rocks and the water will remain cold. If the springs are large, the spring water also will be cold because the volume of water is too great to be adequately warmed. The warmest springs occur when discharges are moderately large, and often are found in regions where the subsurface is unusually warm, such as volcanically active areas.

WATER WELLS..

WELL..A water well is an excavation or structure created in the ground by digging, driving, boring or drilling to access groundwater in underground aquifers. The well water is drawn by an electric submersible pump, a trash pump, a vertical turbine pump, a handpump or a mechanical pump (e.g. from a water-pumping windmill[1]). It can also be drawn up using containers, such as buckets, that are raised mechanically or by hand.

TYPES OF WELLS..

Dug wells Hacking at the ground with a pick and shovel is one way to dig a well. If the ground is soft and the water table is shallow, then dug wells can work. Historically, dug wells were excavated by hand shovel to below the water table until incoming water exceeded the digger's bailing rate . The well was lined with stones, brick, tile, or other material to prevent collapse, and was covered with a cap of wood, stone, or concrete. They cannot be dug much deeper than the water table -- just as you cannot dig a hole very deep when you are at the beach... it keeps filling up with water!

Driven wellsDriven wells are still common today. They are built by driving a small-diameter pipe into soft earth, such as sand or gravel. A screen is usually attached to the bottom of the pipe to filter out sand and other particles. Problems? They can only tap shallow water, and because the source of the water is so close to the surface, contamination from surface pollutants can occur.

Drilled wellsMost modern wells are drilled, which requires a fairly complicated and expensive drill rig. Drill rigs are often mounted on big trucks. They use rotary drill bits that chew away at the rock, percussion bits that smash the rock, or, if the ground is soft,large auger bits. Drilled wells can be drilled more than 1,000 feet deep. Often a pump is placed at the bottom to push water up to the surface.

CAVERNS

A cave or cavern is a natural underground space large enough for a human to enter. Caves form naturally by the weathering of rock and they often extend deep underground. The word "cave" can also refer to much smaller openings such as sea caves, rock shelters, and grottos.

TYPES AND FORMATION

Solutional caveare the most frequently occurring caves and such caves form in rock that is soluble, such as limestone, but can also form in other rocks, including chalk, dolomite, marble, salt, and gypsum. Rock is dissolved by natural acid in groundwater that seeps through bedding-planes, faults, joints and so on. Over geological epochs cracks expand to become caves or cave systems.

Primary caveSome caves are formed at the same time as the surrounding rock. These are sometimes called primary caves

SEA CAVE OR LITTORAL CAVE

Sea caves are found along coasts around the world. A special case is littoral caves, which are formed by wave action in zones of weakness in sea cliffs. Often these weaknesses are faults, but they may also be dykes or bedding-plane contacts. Some wave-cut caves are now above sea level because of later uplift. Elsewhere, in places such as Thailand's Phang Nga Bay, solutional caves have been flooded by the sea and are now subject to littoral erosion. Sea caves are generally around 5 to 50 metres (16 to 160 ft) in length, but may exceed 300 metres (980 ft).

GLACIER CAVE

Glacier caves occur in ice and under glaciers and are formed by melting. They are also influenced by the very slow flow of the ice, which tends to close the caves again. (These are sometimes called ice caves, though this term is properly reserved for caves that contain year-round ice formations).

GEYSERS

A geyser is a spring characterized by intermittent discharge of water ejected turbulently and accompanied by a vapour phase (steam). The word geyser comes from Geysir, the name of an erupting spring at Haukadalur, Iceland; that name, in turn, comes from the Icelandic verb geysa, "to gush“. The formation of geysers is due to particular hydrogeological conditions, which exist in only a few places on Earth, so they are a fairly rare phenomenon. Generally all geyser field sites are located near active volcanic areas, and the geyser effect is due to the proximity of magma.

FORM AND FUNCTIONGeysers are temporary geological features. Geysers are generally associated with volcanic areas.As the water boils, the resulting pressure forces a superheated column of steam and water to the surface through the geyser's internal plumbing. The formation of geysers specifically requires the combination of three geologic conditions that are usually found in volcanic terrain.

Intense heatThe heat needed for geyser formation comes from magma that needs to be near the surface of the earth. The fact that geysers need heat much higher than normally found near the earth's surface is the reason they are associated with volcanoes or volcanic areas. The pressures encountered at the areas where the water is heated makes the boiling point of the water much higher than at normal atmospheric pressures.

WaterThe water that is ejected from a geyser must travel underground through deep, pressurized fissures in the Earth's crust.

A plumbing systemIn order for the heated water to form a geyser, a plumbing system is required. This includes a reservoir to hold the water while it is being heated. Geysers are generally aligned along faults.[3] The plumbing system is made up of a system of fractures, fissures, porous spaces and sometimes cavities. Constrictions in the system are essential to the building up of pressure before an eruption.

GENERAL CATEGORIZATION

Old faithful geyseror cone geyser Erupts approximately91 minutes

Fountain geyser erruptingFrom the pool

END OF SLIDE SHOW..tnxLynnette joy Ulep4bse3_soc.sci