Our valley of the sun was formed as part of the Basin and Range
disturbance, which means that in between the mountains such as the
Estrellas, Camelback Mountain and Mummy Mountain, there are deep
valleys that have filled in with soil over time. This gives us the
flat desert floor we live on. In the west valley, a salt deposit
formed somewhere between 12- 15 million years ago. This deposit,
known as the Luke Salt Deposit, contains over 15 cubic miles of
salt. It may be as thick as 10,000 feet. No one has drilled to its
bottom yet to be sure.
Forming a roughly triangular shape, the deposit’s southwest
corner is near Cotton and Indian School, the northern corner is in
El Mirage, and the southeastern corner is near 99th Avenue and
McDowell Road. The center, where it is at its deepest, is Glendale
and Dysart Roads. Not surprisingly, Morton Salt has a mining
operation there. The plant pumps water into the salt deposit. The
salt dissolves and the saturated fluid (brine) is pumped out into
evaporation ponds. The salt from this operation is used for
industrial purposes and not as table salt. Caverns dissolved in the
subsurface salt are used to store liquefied petroleum gas. These
are the 2 main industries that use the salt deposit here and
elsewhere in our state. Sometime in the future, natural gas may
also be stored in the left over caverns.
The thickest known salt deposits are in the deep intermountain
basins in the Basin and Range Province, which includes the Phoenix
area. Twelve to fifteen million years ago, our valley, only
partially filled with the sediments, filled with one or more vast
lakes. These lakes never drained out to sea. In time, the water
evaporated and formed the salt deposit in a non marine environment
in the Miocene time period. The Luke Salt Deposit is believed to be
one of the 3 thickest bedded evaporite deposit in the world. The
other 2 are also in Arizona. One, near Kingman is sodium chloride.
The other, near Eloy, is anhydrite salt, a calcium sulfite salt.
The Luke Salt Deposit begins only 500 feet below the surface of the
ground and maybe as much as 10,000 feet thick.
Salt is plastic in nature and has a low density compared to the
surrounding soils. It is also quite buoyant. The salt deposit tends
to bulge upwards. The small hills you will see at the coordinates
are the results of soil that has been pushed up by salt
deposit.
To claim credit for this earthcache, please take a photo of
the low rolling hills, either the field south of you, or across
Litchfield Road. Also please email me the estimated height of the
tallest mound you can see. All logs without photos will be deleted
effective Jan 23rd 2006. Please do not go onto the properties
to look at the hills closely. You can get a better appreciation for
them from where you are, on the side street.
Please
visit AZGeocaching.com link here