The Oasis of Mara is located directly behind the
Twentynine Palms Visitor Center. The trail is completely paved
and is handicapped accessible.
Please note, all water sources in the park are protected and
reserved for wildlife.
Many of the oasis and springs in Joshua Tree are related to
faults. Faults not only create a barrier for movement of water from
one side of the fault to the other, but also create cracks for
movement along the fault.
As rocs move past each other along fault lines, the rocks on
either side of the fault get ground up into very tiny pieces. Over
time the rocks along the fault line are ground up into a powder
called fault gouge (See Fault trail in Black Rock Campground) that
act like a dam to horizontal groundwater flow. At the same time,
the fault represents a crack in the ground. Water moves along the
crack easier than it does across the crack.
In the case of the Oasis of Mara, the Pinto
Mountain Fault runs just about east-west and relatively
straight down into the ground. Ground water flowing downhill
backs up on the uphill side of the fault and rises to the
surface along the line of the fault. The palms and green
vegetation that make up the oasis clump along the line of the
fault.
There is another feature that marks the location of the fault.
The paved trail is built on the uphill side of a fault scarp. The
scarp is the relatively steep slope marking the movement of the
fault where one side of the fault moved up relative to the other.
These scarps gradually erode away.
It is though that recent movements along the Pinto Mountain
Fault have changed the flow of water at the oasis. Currently there
is no natural water at the oasis, but groundwater is close enough
to the surface to maintain the greenery.
Logging requirements:
Send me a note with :
- The text "GC1G4QB Oasis of Mara" on the first line
- The number of people in your group.
- About how wide is the oasis compared to its length?
- What direction is the land at the given coordinates moving as a
result of the Pinto Mountain Fault?
- About how high is the scarp at this point?
- When was natural surface water last observed at the
oasis?
The following sources were used to generate this
cache:
- Trent, D.D. & Richard W. Hazlett, Joshua
Tree National Park Geology, Joshua Tree National Park Association,
2002
- Eric H Christiansen and W. Kenneth Hamblin,
2008, Earth's Dynamic Systems, Web Edition 1.0 Groundwater Systems;
http://earthds.info/pdfs/EDS_13.PDF
- Lorence G. Collins, LARGE-SCALE K- AND
Si-METASOMATISM TO FORM THE MEGACRYSTAL QUARTZ MONZONITE AT
TWENTYNINE PALMS, CALIFORNIA, February 15, 1997
http://www.csun.edu/~vcgeo005/29palms.htm
Placement approved by the
Joshua Tree National Park