We spent the MLK weekend visiting our almost one year old grandson (and family) in California. One day, we traveled across the Santa Cruz mountains to the ocean and visited a small state park, Natural Bridges State Beach with its namesake natural bridge sitting just a little bit off shore. I will admit, I was too busy making faces and goofy sounds and generally playing grandfather with the baby to notice when we crossed over from the North American Plate to the Pacific Plate. I guess I will pay more attention on the next visit.
Once at the state park we spent some time exploring the beach. Having spent most of my geology career in Colorado and Utah, I find visiting a current beach to be lots of fun. The beaches I usually frequent were sea side back in the Permian.
The rock was a fun mudstone. A very fine grained sedimentary rock, Miocene in age. Again, I am used to pretty soft sedimentary rock in the canyons of Utah. This mudstone was, pardon the expression, rock hard! The cementing agent of SiO2 has created a very erosion resistant rock that made some great tide pools, ocean side cliffs and
... of course the natural bridges. In the recent (historical) past there were three bridges present. Two have succumbed to the power of erosion leaving the sole remaining bridge, for now. Reading a web site from the University at Santa Cruz the author suggests that the bridges have been transformed from a natural wonder into an educational resource.As for being on the Pacific plate. It didn't feel very different, but I thought I could just faintly detect a little more northward motion instead of the constant westward traveling I have been doing my whole life.