FLOWING ARTESIAN
WELL
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.
In order to log this earthcache you
must:
1. Post a new photo of yourself (including
your face) at the well holding your GPSr, at the time you post your
found it log.
2. Estimate the flow of
water from the well in terms of gallons per minute. To do this you
will need a container of known volume and a watch with a second
hand. Email the Result to the Cache Owner.
All photographs copyright 2006 by RikTu Outfitters
GAG PHOTOS WILL NOT BE ACCEPTED
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