Not New Jersey's Fault

Ross teaches a Geology Lab at CSUSB, including an extra-credit/makeup lab... a hike up to the San Andreas Fault. I have heard all about "the hike" since we started dating (about 8 years ago), but this past Saturday was the first time I actually got to see it for myself.

We went up to the school to meet the students for 10 am. There wasn't a big turnout, just twelve students... probably because the forecast was for light rain.

 

This NASA photo shows the San Andrea Fault , the Arrowhead
Springs Fault, and their proximity to the CSUSB campus.

We’ve all heard that one day California will experience “The Big One.” This, of course, refers to a major earthquake and it is widely assumed this will happen on the San Andreas fault, which passes less than a mile north of the CSUSB campus. The lab is designed to familiarize students with this fault, and to teach about fault characteristics in general.

We learned that  the straight line of the base of the mountain, along with a straight line of trees,  may be the result of faulting.

We also learned the significance of the presence of Pelona schist, which is lithologically identical to the Orocopia schist. There is no Pelona schist in the San Bernardino Mountains. The Pelona schist is on the Pacific Plate, and the Orocopia schist is on the North American Plate, indicating that the two were originally from the same location.

There was also a water channel that could be traced all the way to the line of trees, but which ended abruptly, with no apparent source for the water that eroded it; direct evidence of faulting.

We finally got to a point where there were changes in soil color, and fine-grained fragmented rocks underfoot. We were in the San Andreas fault zone! We crossed over the area, from the Pacific plate to the North American tectonic plate!

On the way back, it started to rain.  We hurried back down to the campus. I’m so glad I finally got to experience this!