The ground beneath our feet is not just rock, or at least, not just
one kind of rock. Many different types of rock exist, and they have
very different properties. Often, different types of rocks exist in
horizontal layers beneath the land surface. Some layers are more porous than others, and at a certain
depth below ground the pores and fractures in
these rocks can be totally filled with water
(an aquifer). When precipitation
falls and seeps into the ground, it moves downward
until it hits a rock layer,
which is so dense and unfractured that it won't allow water to easily
move through it. When this happens it is easier for the water to start
moving horizontally across the more porous rock layer. Sometimes when
building a road, the layers are cut into and revealed, and water can
be seen dripping out through the exposed layers.
Measuring water
Human's influence
Water use
Water Science home page
U.S. Department of the Interior | U.S. Geological Survey
URL: http://ga.water.usgs.gov/edu/gwroadcut.html
Page Contact Information: Howard Perlman
Page Last Modified: Friday, 07-Nov-2008 15:43:43 EST
