Artesians EarthCache
Hidden : 4/14/2008
Difficulty:
1 out of 5
Terrain:
1.5 out of 5

Size: Size: not chosen (not chosen)

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Geocache Description:





Be sure to bring a gallon jug along, a thermometer, and a way to measure time with you for this one.

The water in an artesian well flows from an aquifer, which is a layer of very porous rock or sediment, usually sandstone, capable of holding and transmitting large quantities of water. Artesian springs can occur in similar fashion where faults or cracks in the overlying impervious layer allow water to flow upward.

Artesian wells are deep-drilled wells through which water is forced upward under pressure. The water in an artesian well flows from an aquifer, which is a layer of very porous rock or sediment, usually sandstone, capable of holding and transmitting large quantities of water.



The geologic conditions necessary for an artesian well are an inclined aquifer sandwiched between impervious rock layers above and below that trap water in it. Water enters the exposed edge of the aquifer at a high elevation and percolates downward through interconnected pore spaces. The water held in these spaces is under pressure because of the weight of water in the portion of the aquifer above it. If a well is drilled from the land surface through the overlying impervious layer into the aquifer, this pressure will cause the water to rise in the well. In areas where the slope of the aquifer is great enough, pressure will drive the water above ground level in a spectacular, permanent fountain.

Artesian springs can occur in similar fashion where faults or cracks in the overlying impervious layer allow water to flow upward. Water from an artesian well or spring is usually cold and free of organic contaminants, making it desirable for drinking. In North America, the Dakota sandstone provides aquifers for an artesian system that underlies parts of the Dakotas, Montana, Wyoming, Kansas, Nebraska, and Saskatchewan and supplies great quantities of water to the dry Great Plains region. Many East Coast cities derive their water supplies from aquifers that are exposed along the edge of the Piedmont and dip downward toward the Atlantic coast.

The largest artesian system in the world underlies nearly all of Eastern and Southern Australia. Other important artesian systems serve London, Paris, and East Algeria.

The aquifer that supplies this well cannot be steep as Indiana does not have that many hills. But as you approach the well, you will see that the water is shot out at a high volume. The height would be nice to see, but as you approach the well, you will see the the structure of the well prohibits the water from shooting into the air. The only explanation for the high volume is that the aquifer must be huge.

The word artesian comes from the French town and province of Artois (called Artesium during Roman times) near Calais, where the first European artesian well was drilled in A.D. 1126, by Carthusian monks, and is still flowing today. The term artesian can be applied to any system in which groundwater is confined and builds up high hydrostatic (fluid) pressure. Water in such a system is able to rise above the level of the aquifer if a well is drilled through the confining layer (aquiclude), thereby reducing the pressue and forcing the water upward. For an artesian system to develop, three geologic conditions must be present. 1.the aquifer must be confined above and below to prevent water from escaping 2.the rock sequence is usually tilted and exposed at the surface, enabling the aquifer to be recharged 3.there is suffient precipitation in the recharge zone to keep the aquifer filled The elevation of the water table in the recharge area and the distance of the well head from the recharge area determine the height to which artesian water rises in a well. The surface defined by the water table in the recharge area, called the artesian-pressure surface, is indicated by the sloping dashed line in the figure.
An artesian well will flow freely at the ground surface only if the wellhead is at an elevation below the artesian pressure surface. In this situation, the water flows out of the well because it rises toward the artesian-pressure surface, which is at a higher elevation than the wellhead. In addition to artesian wells, many artesian springs also exist. Such springs can occur if a fault or fracture intersects the aquifer allowing water to rise above the aquifer. Because the geologic conditions necessary for artesian water can occur in a variety of ways, artesian systems are quite common in many areas of the world underlain by sedimentary rock.

To log this EarthCache, you must:
1. Post a picture of yourself and your GPS at this Artesian well.
2. Email me your estimate of the rate, gallons per minute, at which the well is pumping out water. This can be done by bringing a one gallon jug, and a watch with a second hand. Then, you simply time how long it takes to fill the one gallon jug.
3. Email the difference of air temperature to water temperature. To do this measure the air temperature, measure the water temperature, calculate the difference.


THIS EARTHCACHE WAS PLACED BY A
PLATINUM EARTHCACHE MASTER



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