Note: There are only a few ECs in this series. Unfortunately, most of the Maacama Fault is on private property and not accessible, which limits the number of ECs I can create in this series.
The Maacama fault is a right lateral strike-slip fault*. It is considered the north-most portion of the series of faults that includes the Rogers Creek fault (south of Maacama Fault to San Pablo Bay) and the Hayward Fault (from Pt Pinole on San Pablo Bay to Fremont). Most of the Maacama Fault has a creep of about 8 millimeters per year (8 mm/yr or about 0.32 inches/yr). However, this fault also can and has produced earthquakes. Also, the Maacama fault is really a broad zone of semi-parallel faults and for the most part not one discrete fault.
Look due west across the valley and Hwy 101. The large hillslope you see on the otherside of Long Creek & Highway 101 is termed a Shutter Ridge. This is a process similar to what created the Beheaded Drainage at Maacama Fault Series #1: Beheaded (GC8YCB6). Rather than chopping up a drainage here as the fault moved laterally the fault sliced a ridge. That is, there was a ridge that extended across the fault and as the fault moved it moved the two opposite sides of the fault away from each other. The slope opposite you is the face of the ridge where it was “sliced.” Here there are several traces of the fault mostly mapped near the top of the ridge.
To log this and any EarthCache you must answer the questions below and send them to the Cache Owner (me). Once you make the observations please log the cache immediately. I will only contact you if there is a problem with your answers. I am very free with any good faith attempt to answer the questions even if wrong. I have only deleted logs when I can determine that the logger is BS-ing and I can determine they did not actually physically visit the site.
Question #1: Estimate (guess) the height of the Shutter Ridge face from Long Valley Creek at the bottom to the top of the Shutter Ridge face. Trees may confound you’re guess, but do your best. All good faith efforts will be honored.
*A right lateral strike-slip fault is a fault that moves laterally where if you stand on one side of the fault facing the opposite side of the fault, that opposite side of the fault moves to the right relative to the side you are standing on.
Reference:
Pampeyan. E.H.; P.W. Harsh, and J.M. Coakley. 1981. “Preliminary map showing recently active breaks along the Maacama Fault zone between Hopland and Laytonville, Mendocino County, California: Miscellaneous Field Studies Map 1217.” United States Geological Survey.
U.S Geological Survey. U.S. Quaternary Fault Map. [Web Page} https://usgs.maps.arcgis.com/apps/webappviewer/index.html?id=5a6038b3a1684561a9b0aadf88412fcf