This EC is part of a larger series of ECs all focusing on features of the Hayward Fault. There is a final cache in the series (xxx) that can only be logged once you visited all the others in the series. Also, if you're interested in logging the final it is recommended you check out final in advance since observations you've made at this cache and other caches in the series will be helpful/required to log the final. Each of the ECs in the series contains slightly different information regarding the fault, with some overlap. Please see the Geotour for more information on this series (xxx).
The Hayward Fault is a splay off a the Calaveras Fault in the vicinity of San Jose, and the Calaveras Fault originates off the San Andreas Fault at a bend in the vicinity of Hollister (Figure of faults in the Bay Area http://i41.servimg.com/u/f41/16/31/61/01/haywar10.jpg ). The Hayward Fault starts in the vicinity of east of San Jose and extends at the foot of the East Bay Hills until disappears under San Pablo Bay at Point Pinole. The Hayward Fault is what is referred to as a right lateral strike-slip fault; this means that if standing on one side of the fault facing the other side of the fault, the opposite moves laterally (horizontally) to the right of the side your standing on.
At this cache you'll be able to observe several features where the fault has caused other deformation indirectly associated with the motion on the fault. Within Point Pinole uplift, tilting of the land surface, and effect of earthquakes can be observed.
You may log this cache once you find AND send to the CO in an email answers to the questions below. Please also include the name of the cache and GC code in the subject line.
GZ: There is nothing to log or respond to the cache owner at GZ, but this represents the start of your EC of the Hayward Fault at Point Pinole. When you get to the footbridge over the rail line, look south. Right at the change in slope from a steep to more shallow grade is Hayward Fault passes along the toe of the slope.
Way Point #1: At GZ a very small sea (bay) cliff can be observed. This location cannot easily be access at peak tide, and you should visit somewhere between mid-tide and low tide. This mini sea cliff exposes the uplifted bedrock. In the slope above the bedrock you observe, buried under landslide materials, peat/organic rich layers represent the former bay land mud flats were excavated in the past. Radio carbon dating of organics in this layer indicate that this peat was uplifted approximately 1300 years ago. It is believed that these soils were uplifted in a single earthquake event at that time.
Question #1: Describe the bedrock you observe in this mini-"sea" cliff
Way Point #2: Look up the hill. This knoll is formed by uplift on the Hayward Fault.
Question #2: Estimate the elevation difference from the top of the knoll to the current sea level.
Way Point #3. You are looking across the uplift caused by the fault. The trace of the fault is not exposed at this location due to landslides that are believed to be earthquake induced.
Question #3: Characteristic landslide features can be observed in this terrain. Describe the landslide terrain.
Way Point #4. From out on the fishing pier, look back at Point Pinole. Notice the tilt to the land surface. This tilting is cause by compressive forces on the Hayward Fault that is towards the right side of the point from your current vantage point. Now look north across San Pablo Bay, you will see a set of hills trending northwest on the east side Petaluma River Valley. At the west foot of these hills is the Rogers Creek Fault. Because it is not right in line with the Hayward Fault the Rogers Creek Fault is not considered a direct continuation of the Hayward Fault, but is still considered a continuation of the motion on the Hayward Fault.
Question #4: In what cardinal compass direction is the land surface tilting? Estimate the angle of the dip.