The Desert Has its Faults EarthCache
The Desert Has its Faults
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This part of the Mojave desert has hundreds of faults. You are now standing on a segment of the second largest fault in California. This is the Garlock Fault.
This Earthcache is on a turnout off the North 395. Presumably this turnout is for cars that are overheating after climbing the long grade. While your car is cooling, please enjoy this Earthcache. The trail leading from it is a Bureau of Land Management (BLM) trail opened to the public as indicated on the brown stake marked RM3. Please do not wander off the trail. If you have any questions, you can contact the Ridgecrest BLM office at 760-384-5400. The staff is very friendly and encourages visitors to the desert
Garlock Fault Zone
Type of Faulting: left-lateral strike-slip
Length: 250 km
Nearest Community: Frazier Park, Tehachapi, Mojave, Johannesburg
Most Recent Surface Ruptures: 1050 A.D. (?) near Tehachapi; 1500 A.D. (?) near Johannesburg (Searles Valley)
Slip Rate: between 2 and 11 mm/yr; probably averages about 7 mm per year
Interval Between Major Ruptures: between 200 and 3000 years, depending on the fault segment
Probable Magnitudes: MW6.8 - 7.6
Other Notes: The Garlock fault zone is one of the most obvious geologic features in southern California, clearly marking the northern boundary of the area known as the Mojave Block, as well as the southern ends of the Sierra Nevada and the valleys of the westernmost Basin and Range province. While no earthquake has produced surface rupture on the Garlock fault in historic times (although cracks opened along a short segment of the fault in 1952, due to the shaking of the Kern County earthquake, and groundwater removal has also triggered slip in the Fremont Valley area), there have been a few sizable quakes recorded along the Garlock fault zone. The most recent was a magnitude 5.7 near the town of Mojave on July 11, 1992. It is thought to have been triggered by the Landers earthquake, just two weeks earlier. At least one fsection of the fault has shown movement by creep in recent years. These facts, along with the freshness of scarps left behind from previous ruptures and the on-going seismicity associated with the fault zone, leave little doubt that the Garlock fault zone will rupture again in the future.
I would like you to take some time and enjoy this part of the desert. If you are posting this as a find, Please email me the answers to 2 of the 4 questions I am asking. You may answer all 4.
1. While standing at the coordinates, look about 100 feet south east. There are several larger boulders on the ridge. What color are they?
2. What type of rock is it? Bonus: Why do you suppose so many of this type of rock are in this desert.
3. Take a walk about 100 feet down the trail marked RM3. This is open to the public. Just to the west of this trail are hundreds of a small type of rock. What color are they?
4. Why is this rock inherent to this part of the desert?
Please email me the answer to at least 2 of these questions. Do not post them as a log.
Most of all, take some time and enjoy the beauty of the different faults as they go through the desert. If not for them, our area would be flat like Kansas.
Additional Hints
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